1000 Physics & Electricity MCQs with Answers and Explanation

Electricity

Q1. Electric charge is a:

(a) Scalar quantity ✅

(b) Vector quantity

(d) None

Explanation: Charge has magnitude but no direction.

Q2. SI unit of electric charge is:

(a) Coulomb ✅

(b) Ampere

(d) Ohm

Explanation: 1 Coulomb = charge transported by 1 A in 1 s.

Q3. Charge of one electron is:

(a) –1.6 × 10⁻¹⁹ C ✅

(b) +1.6 × 10⁻¹⁹ C

(d) 1 C

Explanation: Electron carries negative elementary charge.

Q4. Charge is quantized because:

(a) It exists in integral multiples of e ✅

(b) It varies continuously

(d) None

Explanation: q = ne, where n is integer.

Q5. Charge is conserved in:

(a) All physical processes ✅

(b) Only chemical reactions

(d) None

Explanation: Total charge before and after remains constant.

Q6. Like charges:

(a) Repel each other ✅

(b) Attract each other

(d) None

Explanation: Electrostatic force is repulsive for like charges.

Q7. Unlike charges:

(a) Attract each other ✅

(b) Repel each other

(d) None

Explanation: Opposite charges experience attractive force.

Q8. Charging by friction involves:

(a) Transfer of electrons ✅

(b) Creation of charge

(d) None

Explanation: One body loses electrons, other gains.

Q9. Charging by conduction requires:

(a) Direct contact ✅

(b) No contact

(d) None

Explanation: Charge flows between touching bodies.

Q10. Charging by induction involves:

(a) Rearrangement of charges ✅

(b) Direct contact

(d) None

Explanation: Nearby charged body induces redistribution.

Q11. Conductors allow:

(a) Free movement of charges ✅

(b) No movement

(d) None

Explanation: Electrons move freely in conductors.

Q12. Insulators:

(a) Do not allow free charge movement ✅

(b) Conduct electricity

(d) None

Explanation: Electrons are tightly bound.

Q13. Grounding a charged body:

(a) Neutralizes it ✅

(b) Increases charge

(d) None

Explanation: Excess charge flows to Earth.

Q14. Electroscope detects:

(a) Presence of charge ✅

(b) Mass

(d) None

Explanation: Divergence of leaves indicates charge.

Q15. SI unit of current is:

(a) Ampere ✅

(b) Coulomb

(d) Ohm

Explanation: 1 A = 1 C/s.

Q16. Current is defined as:

(a) Rate of flow of charge ✅

(b) Rate of flow of energy

(d) None

Explanation: I = Q/t.

Q17. Direction of conventional current is:

(a) Positive to negative ✅

(b) Negative to positive

(d) None

Explanation: Opposite to electron flow.

Q18. Electron flow is:

(a) Negative to positive ✅

(b) Positive to negative

(d) None

Explanation: Electrons move opposite to conventional current.

Q19. Static electricity involves:

(a) Stationary charges ✅

(b) Moving charges

(d) None

Explanation: Charges accumulate without flow.

Q20. Electric field is:

(a) Force per unit charge ✅

(b) Energy per unit charge

(d) None

Explanation: E = F/q.

Q21. Unit of electric field:

(a) N/C ✅

(b) V

(d) Ohm

Explanation: Derived from E = F/q.

Q22. Electric field lines start from:

(a) Positive charge ✅

(b) Negative charge

(d) None

Explanation: Lines originate from positive and terminate at negative.

Q23. Electric field lines never:

(a) Intersect ✅

(b) Curve

(d) None

Explanation: Unique direction at each point.

Q24. Electric dipole consists of:

(a) Equal and opposite charges separated by distance ✅

(b) Two like charges

(d) None

Explanation: Dipole moment = q × 2d.

Q25. Dipole moment is a:

(a) Vector quantity ✅

(b) Scalar quantity

(d) None

Explanation: Direction from negative to positive charge.

Q26. Coulomb’s law states that the force between two point charges is:

(a) Directly proportional to product of charges and inversely proportional to square of distance ✅

(b) Directly proportional to distance

(d) None

Explanation: F = k q₁q₂ / r², where k = 1/(4πϵ₀). The force depends on the medium’s permittivity and decreases rapidly with distance squared.

Q27. Coulomb’s law is similar to:

(a) Newton’s law of gravitation ✅

(b) Ohm’s law

(d) None

Explanation: Both are inverse square laws. Difference: gravitational force is always attractive, electrostatic can be attractive or repulsive.

Q28. Unit of Coulomb’s constant k is:

(a) N·m²/C² ✅

(b) N/C

(d) None

Explanation: Derived from F = k q₁q₂ / r². It ensures dimensional consistency of force in Newtons.

Q29. Permittivity of free space (ϵ₀) value is:

(a) 8.85 × 10⁻¹² C²/(N·m²) ✅

(b) 9 × 10⁹ N·m²/C²

(d) None

Explanation: ϵ₀ is fundamental constant that determines strength of electric interactions in vacuum.

Q30. Electrostatic force is:

(a) Conservative ✅

(b) Non-conservative

(d) None

Explanation: Work done is path independent. Potential energy can be defined for charge configurations.

Q31. Superposition principle states:

(a) Net force is vector sum of individual forces ✅

(b) Net force is scalar sum

(d) None

Explanation: Electrostatic forces add vectorially; each pair acts independently without altering others.

Q32. Electric field at a point is defined as:

(a) Force per unit positive test charge ✅

(b) Energy per unit charge

(d) None

Explanation: E = F/q. Direction is the force experienced by a positive test charge.

Q33. Unit of electric field is:

(a) N/C or V/m ✅

(b) Ampere

(d) None

Explanation: Both units are equivalent since 1 V/m = 1 N/C.

Q34. Electric field due to point charge is:

(a) E = kq/r² ✅

(b) E = q/r

(d) None

Explanation: Derived from Coulomb’s law. Field decreases with square of distance.

Q35. Direction of electric field lines:

(a) Outward from positive, inward to negative ✅

(b) Random

(d) None

Explanation: Conventionally, field lines show direction of force on positive test charge.

Q36. Electric field lines never:

(a) Intersect ✅

(b) Curve

(d) None

Explanation: At any point, field has unique direction. Intersection would imply two directions simultaneously, impossible.

Q37. Electric dipole consists of:

(a) Equal and opposite charges separated by distance ✅

(b) Two like charges

(d) None

Explanation: Dipole moment p = q × 2d. Vector points from negative to positive charge.

Q38. Dipole moment is:

(a) Vector quantity ✅

(b) Scalar quantity

(d) None

Explanation: Magnitude = q × separation, direction from –q to +q.

Q39. Electric field due to dipole at axial point:

(a) E = (2kp)/r³ ✅

(b) E = kp/r²

(d) None

Explanation: Stronger along axis, decreases as cube of distance.

Q40. Electric field due to dipole at equatorial point:

(a) E = (–kp)/r³ ✅

(b) E = (2kp)/r³

(d) None

Explanation: Field is opposite to dipole moment direction, weaker than axial.

Q41. Torque on dipole in uniform field:

(a) τ = pE sin θ ✅

(b) τ = pE cos θ

(d) None

Explanation: Dipole experiences torque tending to align with field.

Q42. Work done in rotating dipole:

(a) W = pE (cos θ₁ – cos θ₂) ✅

(b) W = pE sin θ

(d) None

Explanation: Work depends on initial and final orientation angles.

Q43. Potential energy of dipole in uniform field:

(a) U = –pE cos θ ✅

(b) U = pE sin θ

(d) None

Explanation: Minimum when dipole aligns with field (θ = 0).

Q44. Electric flux is defined as:

(a) Φ = E·A cos θ ✅

(b) Φ = EA

(d) None

Explanation: Measures field lines passing through a surface. Unit: N·m²/C.

Q45. Gauss’s law states:

(a) Net flux through closed surface = q/ϵ₀ ✅

(b) Net flux = 0 always

(d) None

Explanation: Relates enclosed charge to electric flux, fundamental in electrostatics.

Q46. Electric field due to infinite line charge:

(a) E = λ/(2πϵ₀r) ✅

(b) E = λ/r²

(d) None

Explanation: Derived using Gauss’s law with cylindrical symmetry.

Q47. Electric field due to infinite plane sheet:

(a) E = σ/(2ϵ₀) ✅

(b) E = σ/ϵ₀

(d) None

Explanation: Field is uniform, independent of distance.

Q48. Electric field inside a conductor:

(a) Zero ✅

(b) Constant

(d) None

Explanation: Charges reside on surface, canceling internal field.

Q49. Electric field just outside conductor surface:

(a) E = σ/ϵ₀ ✅

(b) E = σ/(2ϵ₀)

(d) None

Explanation: Field proportional to surface charge density.

Q50. Electrostatic shielding means:

(a) Electric field inside hollow conductor is zero ✅

(b) Field is maximum

(d) None

Explanation: Conductors block external fields; principle used in Faraday cages.

Q51. Electric potential at a point is defined as:

(a) Work done per unit charge in bringing it from infinity ✅

(b) Force per unit charge

(d) None

Explanation: V = W/q. It represents the potential energy per unit charge at a point in an electric field.

Q52. SI unit of potential is:

(a) Volt ✅

(b) Joule

(d) Ohm

Explanation: 1 Volt = 1 Joule per Coulomb. It measures energy per unit charge.

Q53. Potential due to point charge is:

(a) V = kq/r ✅

(b) V = q/r²

(d) None

Explanation: Derived from work-energy relation. Potential decreases inversely with distance.

Q54. Potential at infinity is taken as:

(a) Zero ✅

(b) Infinite

(d) None

Explanation: Reference point convention. Work is measured relative to infinity.

Q55. Potential energy of two charges is:

(a) U = kq₁q₂/r ✅

(b) U = q₁q₂/r²

(d) None

Explanation: Energy stored in configuration of charges. Positive for like charges, negative for unlike.

Q56. Work done in moving charge between two points:

(a) W = q(V₁ – V₂) ✅

(b) W = qV

(d) None

Explanation: Work depends only on potential difference, not path taken.

Q57. Equipotential surfaces are:

(a) Surfaces of constant potential ✅

(b) Surfaces of constant field

(d) None

Explanation: No work is done in moving charge along equipotential surface.

Q58. Electric field is always:

(a) Perpendicular to equipotential surfaces ✅

(b) Parallel to equipotential surfaces

(d) None

Explanation: Field lines cross equipotential surfaces at right angles.

Q59. Potential due to dipole at axial point:

(a) V = (kp)/r² ✅

(b) V = (2kp)/r³

(d) None

Explanation: Potential decreases as inverse square of distance along axis.

Q60. Potential due to dipole at equatorial point:

(a) V = 0 ✅

(b) V = kp/r²

(d) None

Explanation: Contributions from both charges cancel at equatorial line.

Q61. Potential energy of dipole in uniform field:

(a) U = –pE cos θ ✅

(b) U = pE sin θ

(d) None

Explanation: Energy minimum when dipole aligns with field.

Q62. Potential difference is measured by:

(a) Voltmeter ✅

(b) Ammeter

(d) None

Explanation: Voltmeter is connected in parallel to measure voltage.

Q63. Work done in moving charge in uniform field:

(a) W = qEd ✅

(b) W = qE

(d) None

Explanation: Work = force × displacement = qE × d.

Q64. Potential gradient is defined as:

(a) Rate of change of potential with distance ✅

(b) Rate of change of charge

(d) None

Explanation: E = –dV/dx. Field is negative gradient of potential.

Q65. Potential due to ring of charge at center:

(a) V = kQ/R ✅

(b) V = kQ/R²

(d) None

Explanation: All points on ring are equidistant from center.

Q66. Potential due to uniformly charged sphere outside:

(a) V = kQ/r ✅

(b) V = kQ/R

(d) None

Explanation: Sphere behaves like point charge at center for external points.

Q67. Potential inside uniformly charged sphere:

(a) V = kQ(3R² – r²)/(2R³) ✅

(b) V = kQ/r

(d) None

Explanation: Derived using Gauss’s law. Potential decreases quadratically inside.

Q68. Potential energy of system of charges:

(a) Sum of pairwise energies ✅

(b) Product of charges

(d) None

Explanation: U = Σ kqᵢqⱼ/rᵢⱼ. Superposition principle applies.

Q69. Potential due to infinite line charge:

(a) V = (2kλ) ln(r) ✅

(b) V = λ/r

(d) None

Explanation: Potential grows logarithmically with distance.

Q70. Potential due to infinite plane sheet:

(a) V = σx/ϵ₀ ✅

(b) V = σ/ϵ₀

(d) None

Explanation: Potential increases linearly with distance from sheet.

Q71. Potential difference between two points in field:

(a) V = ∫ E·dr ✅

(b) V = E × d

(d) None

Explanation: Line integral of field gives potential difference.

Q72. Potential energy of charge in field:

(a) U = qV ✅

(b) U = qE

(d) None

Explanation: Energy stored depends on charge and potential at point.

Q73. Potential due to dipole at large distance:

(a) V ∝ 1/r² ✅

(b) V ∝ 1/r³

(d) None

Explanation: Dipole potential decreases faster than point charge potential.

Q74. Potential difference in capacitor plates:

(a) V = Q/C ✅

(b) V = Qd

(d) None

Explanation: Relation between charge, capacitance, and voltage.

Q75. Energy stored in capacitor:

(a) U = ½ CV² ✅

(b) U = CV²

(d) None

Explanation: Derived from work done in charging. Energy proportional to square of voltage.

Q76. Electric current is defined as:

(a) Rate of flow of charge ✅

(b) Rate of flow of energy

(d) None

Explanation: I = Q/t. Current measures how much charge passes through a cross-section per unit time.

Q77. SI unit of current is:

(a) Ampere ✅

(b) Coulomb

(d) Ohm

Explanation: 1 Ampere = 1 Coulomb per second. It is a fundamental SI unit.

Q78. Direction of conventional current is:

(a) Positive to negative ✅

(b) Negative to positive

(d) None

Explanation: By convention, current flows from higher potential to lower potential, opposite to electron flow.

Q79. Electron flow is:

(a) Negative to positive ✅

(b) Positive to negative

(d) None

Explanation: Electrons move opposite to conventional current direction.

Q80. Electric circuit is:

(a) Closed path for current flow ✅

(b) Open path

(d) None

Explanation: Current flows only in a closed conducting loop.

Q81. Open circuit means:

(a) No current flows ✅

(b) Maximum current flows

(d) None

Explanation: Break in path prevents charge movement.

Q82. Closed circuit means:

(a) Current flows ✅

(b) No current flows

(d) None

Explanation: Continuous conducting path allows charge flow.

Q83. Short circuit occurs when:

(a) Resistance becomes very low ✅

(b) Resistance becomes very high

(d) None

Explanation: Large current flows, potentially damaging circuit.

Q84. Series connection of resistors means:

(a) Same current flows through all ✅

(b) Same voltage across all

(d) None

Explanation: Current is constant, voltage divides.

Q85. Parallel connection of resistors means:

(a) Same voltage across all ✅

(b) Same current through all

(d) None

Explanation: Voltage is constant, current divides.

Q86. Equivalent resistance in series:

(a) R = R₁ + R₂ + R₃ ✅

(b) 1/R = 1/R₁ + 1/R₂

(d) None

Explanation: Resistances add directly in series.

Q87. Equivalent resistance in parallel:

(a) 1/R = 1/R₁ + 1/R₂ + 1/R₃ ✅

(b) R = R₁ + R₂

(d) None

Explanation: Reciprocal sum rule applies in parallel.

Q88. Kirchhoff’s current law (KCL) states:

(a) Sum of currents entering junction = sum leaving ✅

(b) Sum of voltages = 0

(d) None

Explanation: Based on conservation of charge.

Q89. Kirchhoff’s voltage law (KVL) states:

(a) Sum of potential differences in closed loop = 0 ✅

(b) Sum of currents = 0

(d) None

Explanation: Based on conservation of energy.

Q90. Ammeter measures:

(a) Current ✅

(b) Voltage

(d) None

Explanation: Connected in series, low resistance.

Q91. Voltmeter measures:

(a) Voltage ✅

(b) Current

(d) None

Explanation: Connected in parallel, high resistance.

Q92. Galvanometer detects:

(a) Small currents ✅

(b) Large currents

(d) None

Explanation: Sensitive instrument for tiny currents.

Q93. Conversion of galvanometer to ammeter requires:

(a) Low resistance shunt ✅

(b) High resistance series

(d) None

Explanation: Shunt bypasses excess current.

Q94. Conversion of galvanometer to voltmeter requires:

(a) High resistance series ✅

(b) Low resistance shunt

(d) None

Explanation: Series resistance limits current, measures voltage.

Q95. Electric fuse works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Excess current melts fuse wire, breaking circuit.

Q96. Electric switch is used to:

(a) Open or close circuit ✅

(b) Measure current

(d) None

Explanation: Controls flow of current.

Q97. Electric relay is:

(a) Electromagnetic switch ✅

(b) Mechanical switch

(d) None

Explanation: Uses electromagnet to control circuit remotely.

Q98. Circuit breaker replaces:

(a) Fuse ✅

(b) Battery

(d) None

Explanation: Automatically trips during overload, reusable.

Q99. Household circuits use:

(a) Parallel connection ✅

(b) Series connection

(d) None

Explanation: Ensures each appliance gets full voltage.

Q100. Series connection in household circuits is avoided because:

(a) One failure breaks entire circuit ✅

(b) Voltage increases

(d) None

Explanation: Appliances would not work independently in series.

Q101. Ohm’s law states:

(a) Current is directly proportional to voltage at constant temperature ✅

(b) Current is inversely proportional to voltage

(d) None

Explanation: V = IR. Resistance remains constant if temperature and physical conditions are unchanged.

Q102. SI unit of resistance is:

(a) Ohm (Ω) ✅

(b) Volt

(d) Watt

Explanation: 1 Ω = 1 Volt / 1 Ampere. It measures opposition to current flow.

Q103. Resistivity depends on:

(a) Material ✅

(b) Length only

(d) None

Explanation: Resistivity (ρ) is a property of material, independent of dimensions.

Q104. Resistance of conductor is:

(a) R = ρL/A ✅

(b) R = ρA/L

(d) None

Explanation: Resistance increases with length, decreases with cross-sectional area.

Q105. Conductivity is reciprocal of:

(a) Resistivity ✅

(b) Resistance

(d) None

Explanation: σ = 1/ρ. High conductivity means low resistivity.

Q106. Good conductors have:

(a) Low resistivity ✅

(b) High resistivity

(d) None

Explanation: Metals like copper, silver have very low resistivity.

Q107. Insulators have:

(a) Very high resistivity ✅

(b) Very low resistivity

(d) None

Explanation: Rubber, glass resist current flow strongly.

Q108. Semiconductors have:

(a) Resistivity between conductors and insulators ✅

(b) Very low resistivity

(d) None

Explanation: Silicon, germanium show intermediate behavior.

Q109. Resistance of metal increases with:

(a) Temperature ✅

(b) Pressure

(d) None

Explanation: More collisions of electrons with ions at higher temperature.

Q110. Resistance of semiconductor decreases with:

(a) Temperature ✅

(b) Pressure

(d) None

Explanation: More charge carriers generated at higher temperature.

Q111. Superconductors have:

(a) Zero resistance below critical temperature ✅

(b) Infinite resistance

(d) None

Explanation: Current flows without energy loss in superconducting state.

Q112. Ohm’s law fails for:

(a) Non-ohmic devices ✅

(b) Metallic conductors

(d) None

Explanation: Devices like diodes, transistors do not obey linear V–I relation.

Q113. V–I graph for ohmic conductor is:

(a) Straight line through origin ✅

(b) Parabola

(d) None

Explanation: Linear relation between voltage and current.

Q114. V–I graph for diode is:

(a) Non-linear ✅

(b) Linear

(d) None

Explanation: Diode conducts only after threshold voltage, showing non-linear curve.

Q115. Resistance of wire depends on:

(a) Length, area, material ✅

(b) Voltage only

(d) None

Explanation: R = ρL/A. Geometry and material determine resistance.

Q116. Resistivity of alloy is:

(a) Higher than pure metal ✅

(b) Lower than pure metal

(d) None

Explanation: Alloys scatter electrons more, increasing resistivity.

Q117. Nichrome is used in heating elements because:

(a) High resistivity and high melting point ✅

(b) Low resistivity

(d) None

Explanation: Can withstand heat without oxidizing quickly.

Q118. Copper is used in wires because:

(a) Low resistivity and high conductivity ✅

(b) High resistivity

(d) None

Explanation: Efficient conductor with minimal energy loss.

Q119. Silver is best conductor because:

(a) Lowest resistivity ✅

(b) Highest resistivity

(d) None

Explanation: Silver has highest electrical conductivity among metals.

Q120. Temperature coefficient of resistance is:

(a) Fractional change per degree rise ✅

(b) Absolute change

(d) None

Explanation: α = ΔR / (RΔT). Indicates sensitivity of resistance to temperature.

Q121. Resistance of insulators with temperature:

(a) Decreases ✅

(b) Increases

(d) None

Explanation: More charge carriers generated, reducing resistance.

Q122. Resistance of metals with temperature:

(a) Increases ✅

(b) Decreases

(d) None

Explanation: Electron scattering increases, raising resistance.

Q123. Ohm’s law is valid only when:

(a) Physical conditions remain constant ✅

(b) Temperature varies

(d) None

Explanation: Linear relation holds under constant temperature and material.

Q124. Conductivity unit is:

(a) Siemens/meter ✅

(b) Ohm

(d) Ampere

Explanation: Reciprocal of resistivity. 1 S/m = 1/Ω·m.

Q125. Resistivity unit is:

(a) Ohm·meter ✅

(b) Siemens

(d) Ampere

Explanation: Derived from R = ρL/A. Indicates material property.

Q126. Resistance of a conductor depends on:

(a) Length, area, and material ✅

(b) Voltage only

(d) None

Explanation: R = ρL/A. Longer wires have more resistance, thicker wires less, and material property (ρ) is crucial.

Q127. Resistance in series connection:

(a) Adds directly ✅

(b) Adds reciprocally

(d) None

Explanation: R_total = R₁ + R₂ + R₃. Current is same, voltage divides across resistors.

Q128. Resistance in parallel connection:

(a) Adds reciprocally ✅

(b) Adds directly

(d) None

Explanation: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃. Voltage is same, current divides.

Q129. Equivalent resistance of two equal resistors in series:

(a) 2R ✅

(b) R/2

(d) None

Explanation: R_total = R + R = 2R.

Q130. Equivalent resistance of two equal resistors in parallel:

(a) R/2 ✅

(b) 2R

(d) None

Explanation: 1/R_total = 2/R → R_total = R/2.

Q131. Series connection is used when:

(a) Higher resistance is needed ✅

(b) Lower resistance is needed

(d) None

Explanation: Adding resistors increases total resistance.

Q132. Parallel connection is used when:

(a) Lower resistance is needed ✅

(b) Higher resistance is needed

(d) None

Explanation: Parallel reduces effective resistance.

Q133. Voltage across series resistors:

(a) Divides in proportion to resistance ✅

(b) Same across all

(d) None

Explanation: V₁ = IR₁, V₂ = IR₂. Larger resistance gets larger share.

Q134. Current through parallel resistors:

(a) Divides in inverse proportion to resistance ✅

(b) Same through all

(d) None

Explanation: I₁ = V/R₁, I₂ = V/R₂. Smaller resistance gets larger current.

Q135. Power dissipation in resistor:

(a) P = I²R ✅

(b) P = IR

(d) None

Explanation: Derived from Joule’s law. Heat generated proportional to square of current.

Q136. Voltage division rule applies to:

(a) Series circuits ✅

(b) Parallel circuits

(d) None

Explanation: Voltage divides among series resistors according to resistance.

Q137. Current division rule applies to:

(a) Parallel circuits ✅

(b) Series circuits

(d) None

Explanation: Current divides among parallel resistors according to resistance.

Q138. Internal resistance of cell affects:

(a) Terminal voltage ✅

(b) Current only

(d) None

Explanation: V = E – Ir. Larger internal resistance reduces voltage available.

Q139. Effective resistance of n equal resistors in series:

(a) nR ✅

(b) R/n

(d) None

Explanation: R_total = R + R + … (n times) = nR.

Q140. Effective resistance of n equal resistors in parallel:

(a) R/n ✅

(b) nR

(d) None

Explanation: 1/R_total = n/R → R_total = R/n.

Q141. Wheatstone bridge works on:

(a) Null deflection principle ✅

(b) Maximum deflection

(d) None

Explanation: Balanced bridge shows zero current in galvanometer.

Q142. Condition for balanced Wheatstone bridge:

(a) R₁/R₂ = R₃/R₄ ✅

(b) R₁ + R₂ = R₃ + R₄

(d) None

Explanation: Ratio of resistances must be equal for no deflection.

Q143. Meter bridge is based on:

(a) Wheatstone bridge principle ✅

(b) Ohm’s law only

(d) None

Explanation: Uses uniform wire to measure unknown resistance.

Q144. Resistance of wire increases if:

(a) Length increases ✅

(b) Area increases

(d) None

Explanation: Longer path increases opposition to current.

Q145. Resistance of wire decreases if:

(a) Area increases ✅

(b) Length increases

(d) None

Explanation: Thicker wire allows more charge flow.

Q146. Variable resistor is called:

(a) Rheostat ✅

(b) Voltmeter

(d) None

Explanation: Used to vary current in circuit.

Q147. Color code of resistor indicates:

(a) Resistance value ✅

(b) Voltage

(d) None

Explanation: Bands represent digits and multiplier for resistance.

Q148. Tolerance in resistor color code means:

(a) Accuracy range ✅

(b) Exact value

(d) None

Explanation: Indicates percentage variation from nominal resistance.

Q149. Potentiometer measures:

(a) Potential difference accurately ✅

(b) Current

(d) None

Explanation: Works on null deflection principle, more accurate than voltmeter.

Q150. Advantage of potentiometer over voltmeter:

(a) No current drawn from circuit ✅

(b) Draws current

(d) None

Explanation: Measures true potential difference without loading circuit.

Q151. Electric power is defined as:

(a) Rate of doing electrical work ✅

(b) Total energy

(d) None

Explanation: Power = Work/time. In circuits, P = VI. It measures how fast electrical energy is converted into other forms.

Q152. SI unit of power is:

(a) Watt ✅

(b) Joule

(d) Ampere

Explanation: 1 Watt = 1 Joule per second. It represents energy conversion per unit time.

Q153. Power in terms of current and resistance:

(a) P = I²R ✅

(b) P = IR

(d) None

Explanation: Derived from P = VI and Ohm’s law (V = IR). Shows heating effect of current.

Q154. Power in terms of voltage and resistance:

(a) P = V²/R ✅

(b) P = VR

(d) None

Explanation: Derived from P = VI and I = V/R. Useful when voltage and resistance are known.

Q155. Energy consumed in time t:

(a) E = Pt ✅

(b) E = P/t

(d) None

Explanation: Energy = Power × time. Measured in Joules or kilowatt-hour.

Q156. Commercial unit of energy is:

(a) Kilowatt-hour ✅

(b) Joule

(d) None

Explanation: 1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J. Used in electricity billing.

Q157. Electric energy meter measures:

(a) Energy consumed ✅

(b) Power only

(d) None

Explanation: Records total electrical energy used over time.

Q158. Efficiency of electrical device is:

(a) Ratio of useful output to input ✅

(b) Ratio of input to output

(d) None

Explanation: η = (Useful power output / Power input) × 100%. Always less than 100%.

Q159. Heating effect of current is explained by:

(a) Joule’s law ✅

(b) Ohm’s law

(d) None

Explanation: Heat produced H = I²Rt. Basis of electric heaters, fuses.

Q160. Electric iron works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Resistance wire converts electrical energy into heat.

Q161. Electric bulb filament works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Tungsten filament glows when heated due to resistance.

Q162. Electric kettle works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Converts electrical energy into heat to boil water.

Q163. Electric fuse works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Excess current melts fuse wire, protecting circuit.

Q164. Electric motor works on:

(a) Magnetic effect of current ✅

(b) Heating effect

(d) None

Explanation: Current in coil produces torque in magnetic field.

Q165. Electric generator works on:

(a) Electromagnetic induction ✅

(b) Heating effect

(d) None

Explanation: Converts mechanical energy into electrical energy.

Q166. Transformer works on:

(a) Electromagnetic induction ✅

(b) Heating effect

(d) None

Explanation: Transfers energy between coils via mutual induction.

Q167. Electric power transmission uses:

(a) High voltage ✅

(b) Low voltage

(d) None

Explanation: High voltage reduces current, minimizing I²R losses.

Q168. Power loss in transmission lines:

(a) P_loss = I²R ✅

(b) P_loss = IR

(d) None

Explanation: Loss depends on square of current and resistance of wires.

Q169. Household power rating indicates:

(a) Maximum power consumption ✅

(b) Minimum power

(d) None

Explanation: Appliances are rated in watts or kilowatts to show energy usage.

Q170. Electric energy stored in capacitor:

(a) U = ½ CV² ✅

(b) U = CV²

(d) None

Explanation: Derived from work done in charging capacitor.

Q171. Electric energy stored in inductor:

(a) U = ½ LI² ✅

(b) U = LI²

(d) None

Explanation: Energy stored in magnetic field of inductor.

Q172. Electric power in AC circuit:

(a) P = VI cos φ ✅

(b) P = VI

(d) None

Explanation: cos φ is power factor. Real power depends on phase angle.

Q173. Apparent power in AC circuit:

(a) S = VI ✅

(b) S = VI cos φ

(d) None

Explanation: Product of RMS voltage and current, measured in VA.

Q174. Reactive power in AC circuit:

(a) Q = VI sin φ ✅

(b) Q = VI cos φ

(d) None

Explanation: Represents energy alternately stored and released by inductors/capacitors.

Q175. Power factor close to 1 means:

(a) Efficient power usage ✅

(b) Inefficient usage

(d) None

Explanation: cos φ ≈ 1 indicates most power is converted to useful work.

Q176. Ammeter is used to measure:

(a) Current ✅

(b) Voltage

(d) None

Explanation: Ammeter is connected in series with circuit elements. It has very low resistance so it doesn’t affect current flow.

Q177. Voltmeter is used to measure:

(a) Voltage ✅

(b) Current

(d) None

Explanation: Voltmeter is connected in parallel across components. It has very high resistance to avoid drawing current.

Q178. Galvanometer detects:

(a) Small currents ✅

(b) Large currents

(d) None

Explanation: Sensitive instrument that shows deflection even for microampere currents. Used in bridge circuits.

Q179. Conversion of galvanometer to ammeter requires:

(a) Low resistance shunt ✅

(b) High resistance series

(d) None

Explanation: Shunt provides alternate path for excess current, protecting galvanometer.

Q180. Conversion of galvanometer to voltmeter requires:

(a) High resistance series ✅

(b) Low resistance shunt

(d) None

Explanation: Series resistance limits current, allowing measurement of voltage.

Q181. Multimeter can measure:

(a) Voltage, current, resistance ✅

(b) Only voltage

(d) None

Explanation: Versatile instrument combining ammeter, voltmeter, and ohmmeter functions.

Q182. Ohmmeter measures:

(a) Resistance ✅

(b) Voltage

(d) None

Explanation: Uses internal battery to measure resistance directly.

Q183. Wattmeter measures:

(a) Power ✅

(b) Energy

(d) None

Explanation: Measures instantaneous electrical power in circuit.

Q184. Energy meter measures:

(a) Energy consumed ✅

(b) Power only

(d) None

Explanation: Records total electrical energy usage over time, used in billing.

Q185. Meter bridge works on:

(a) Wheatstone bridge principle ✅

(b) Ohm’s law only

(d) None

Explanation: Uses uniform wire to measure unknown resistance by balancing ratios.

Q186. Condition for balanced meter bridge:

(a) R₁/R₂ = l₁/l₂ ✅

(b) R₁ + R₂ = l₁ + l₂

(d) None

Explanation: Ratio of resistances equals ratio of wire lengths.

Q187. Potentiometer measures:

(a) Potential difference accurately ✅

(b) Current

(d) None

Explanation: Works on null deflection principle, more accurate than voltmeter.

Q188. Advantage of potentiometer over voltmeter:

(a) No current drawn from circuit ✅

(b) Draws current

(d) None

Explanation: Measures true potential difference without loading circuit.

Q189. Sensitivity of potentiometer increases with:

(a) Length of wire ✅

(b) Short wire

(d) None

Explanation: Longer wire gives smaller potential gradient, increasing accuracy.

Q190. Galvanometer deflection depends on:

(a) Current through coil ✅

(b) Voltage only

(d) None

Explanation: Torque proportional to current in coil placed in magnetic field.

Q191. Ammeter should have:

(a) Low resistance ✅

(b) High resistance

(d) None

Explanation: Prevents altering current in circuit.

Q192. Voltmeter should have:

(a) High resistance ✅

(b) Low resistance

(d) None

Explanation: Prevents drawing current from circuit.

Q193. Shunt resistance in ammeter is:

(a) Very small ✅

(b) Very large

(d) None

Explanation: Provides alternate path for majority of current.

Q194. Series resistance in voltmeter is:

(a) Very large ✅

(b) Very small

(d) None

Explanation: Limits current through galvanometer coil.

Q195. Null deflection method is used in:

(a) Potentiometer ✅

(b) Ammeter

(d) None

Explanation: Balance point found where galvanometer shows zero deflection.

Q196. Accuracy of Wheatstone bridge depends on:

(a) Sensitivity of galvanometer ✅

(b) Resistance only

(d) None

Explanation: More sensitive galvanometer detects small imbalance.

Q197. Resistance box is used to:

(a) Provide known resistances ✅

(b) Measure voltage

(d) None

Explanation: Contains resistors of standard values for experiments.

Q198. Slide wire bridge is another name for:

(a) Meter bridge ✅

(b) Wheatstone bridge

(d) None

Explanation: Uses sliding contact on wire to balance bridge.

Q199. Ammeter is always connected:

(a) In series ✅

(b) In parallel

(d) None

Explanation: Measures current flowing through circuit element.

Q200. Voltmeter is always connected:

(a) In parallel ✅

(b) In series

(d) None

Explanation: Measures potential difference across component.

Q201. Transformer works on:

(a) Electromagnetic induction ✅

(b) Heating effect

(d) None

Explanation: A transformer transfers energy between two coils by mutual induction. It requires alternating current (AC) to function.

Q202. Transformer is used to:

(a) Step up or step down voltage ✅

(b) Measure current

(d) None

Explanation: Step-up increases voltage, step-down decreases voltage, while maintaining power (neglecting losses).

Q203. Core of transformer is made of:

(a) Soft iron ✅

(b) Copper

(d) None

Explanation: Soft iron provides low reluctance path for magnetic flux, improving efficiency.

Q204. Efficiency of transformer is:

(a) Ratio of output power to input power ✅

(b) Ratio of input to output

(d) None

Explanation: η = (P_out / P_in) × 100%. Ideally close to 100%.

Q205. Losses in transformer include:

(a) Copper and iron losses ✅

(b) Only copper losses

(d) None

Explanation: Copper losses due to resistance of windings; iron losses due to hysteresis and eddy currents.

Q206. Copper loss in transformer is:

(a) I²R loss in windings ✅

(b) Hysteresis loss

(d) None

Explanation: Resistance of coils causes heating when current flows.

Q207. Iron loss in transformer is due to:

(a) Hysteresis and eddy currents ✅

(b) Copper resistance

(d) None

Explanation: Alternating flux in core causes energy loss.

Q208. Laminated core reduces:

(a) Eddy current loss ✅

(b) Copper loss

(d) None

Explanation: Thin laminations increase resistance to eddy currents, minimizing loss.

Q209. Alternating current (AC) means:

(a) Current changes direction periodically ✅

(b) Current flows in one direction

(d) None

Explanation: AC reverses direction and magnitude with time, unlike DC.

Q210. Direct current (DC) means:

(a) Current flows in one direction only ✅

(b) Current changes direction

(d) None

Explanation: DC is steady, produced by batteries and cells.

Q211. Frequency of AC in India is:

(a) 50 Hz ✅

(b) 60 Hz

(d) None

Explanation: AC completes 50 cycles per second in India.

Q212. Frequency of AC in USA is:

(a) 60 Hz ✅

(b) 50 Hz

(d) None

Explanation: Standard frequency in USA is 60 cycles per second.

Q213. RMS value of AC is:

(a) Effective value producing same heating as DC ✅

(b) Peak value

(d) None

Explanation: RMS = V₀/√2. It represents equivalent DC value.

Q214. Average value of AC over half cycle:

(a) 0.637 V₀ ✅

(b) 0.707 V₀

(d) None

Explanation: Average value is derived from integration over half cycle.

Q215. Peak value of AC is:

(a) Maximum instantaneous value ✅

(b) RMS value

(d) None

Explanation: Denoted by V₀ or I₀. Occurs at crest of sine wave.

Q216. Relation between RMS and peak value:

(a) V_rms = V₀/√2 ✅

(b) V_rms = V₀

(d) None

Explanation: Effective value is 0.707 times peak value.

Q217. Power in pure resistive AC circuit:

(a) P = VI ✅

(b) P = 0

(d) None

Explanation: Voltage and current are in phase, so power factor = 1.

Q218. Power in pure inductive AC circuit:

(a) Zero ✅

(b) Maximum

(d) None

Explanation: Voltage leads current by 90°, average power = 0.

Q219. Power in pure capacitive AC circuit:

(a) Zero ✅

(b) Maximum

(d) None

Explanation: Current leads voltage by 90°, average power = 0.

Q220. Power factor is defined as:

(a) cos φ ✅

(b) sin φ

(d) None

Explanation: φ is phase angle between voltage and current. Determines efficiency.

Q221. Leading power factor occurs in:

(a) Capacitive circuits ✅

(b) Inductive circuits

(d) None

Explanation: Current leads voltage in capacitive load.

Q222. Lagging power factor occurs in:

(a) Inductive circuits ✅

(b) Capacitive circuits

(d) None

Explanation: Current lags voltage in inductive load.

Q223. Apparent power is:

(a) Product of RMS voltage and current ✅

(b) Real power

(d) None

Explanation: S = VI. Measured in volt-ampere (VA).

Q224. Real power is:

(a) P = VI cos φ ✅

(b) P = VI

(d) None

Explanation: Portion of power actually consumed or converted into work.

Q225. Reactive power is:

(a) Q = VI sin φ ✅

(b) Q = VI cos φ

(d) None

Explanation: Represents energy alternately stored and released by inductors/capacitors.

Q226. Electric bulb works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Current through filament produces heat due to resistance. At high temperature, filament glows and emits light.

Q227. Filament of electric bulb is made of:

(a) Tungsten ✅

(b) Copper

(d) None

Explanation: Tungsten has high melting point (~3400°C) and resists oxidation, making it ideal for glowing filaments.

Q228. Inert gas inside bulb is:

(a) Argon or nitrogen ✅

(b) Oxygen

(d) None

Explanation: Prevents oxidation of filament and reduces evaporation, prolonging bulb life.

Q229. Bulb efficiency is low because:

(a) Most energy converted to heat ✅

(b) Most energy converted to light

(d) None

Explanation: Only ~5–10% of energy becomes light, rest is wasted as heat.

Q230. Power rating of bulb indicates:

(a) Energy consumed per second ✅

(b) Voltage only

(d) None

Explanation: Wattage shows how much electrical power bulb uses.

Q231. Brightness of bulb depends on:

(a) Power rating ✅

(b) Resistance only

(d) None

Explanation: Higher wattage bulbs emit more light at rated voltage.

Q232. CFL bulbs are more efficient because:

(a) Less heat, more light ✅

(b) More heat, less light

(d) None

Explanation: Compact fluorescent lamps convert more energy into visible light.

Q233. LED bulbs are efficient because:

(a) Use electroluminescence ✅

(b) Use heating effect

(d) None

Explanation: Light emitted directly by electrons recombining in semiconductor, minimal heat loss.

Q234. Heating effect of current is used in:

(a) Electric heater ✅

(b) Electric motor

(d) None

Explanation: Resistance wires convert electrical energy into heat.

Q235. Joule’s law of heating states:

(a) Heat ∝ I²Rt ✅

(b) Heat ∝ IR

(d) None

Explanation: Heat produced depends on square of current, resistance, and time.

Q236. Electric iron works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Resistance coil heats up, transferring heat to iron plate.

Q237. Electric kettle works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Resistance element heats water quickly.

Q238. Electric toaster works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Nichrome wires glow red, toasting bread.

Q239. Electric geyser works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Resistance coil heats water stored in tank.

Q240. Electric fuse works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Excess current melts fuse wire, breaking circuit.

Q241. Fuse wire is made of:

(a) Tin-lead alloy ✅

(b) Copper

(d) None

Explanation: Low melting point ensures quick response to overload.

Q242. Rating of fuse depends on:

(a) Maximum current it can carry ✅

(b) Voltage only

(d) None

Explanation: Fuse must match current capacity of circuit.

Q243. Electric heater coil is made of:

(a) Nichrome ✅

(b) Copper

(d) None

Explanation: Nichrome has high resistivity and withstands high temperatures.

Q244. Electric bulb filament is coiled because:

(a) Increases length, reduces evaporation ✅

(b) Reduces length

(d) None

Explanation: Coiling increases effective length, reducing filament evaporation.

Q245. Efficiency of LED bulbs is:

(a) Very high ✅

(b) Very low

(d) None

Explanation: LEDs convert most electrical energy into light, minimal heat loss.

Q246. Incandescent bulbs are being replaced by:

(a) CFLs and LEDs ✅

(b) Motors

(d) None

Explanation: CFLs and LEDs are more energy-efficient and durable.

Q247. Electric heating appliances use:

(a) High resistance wires ✅

(b) Low resistance wires

(d) None

Explanation: High resistance ensures sufficient heat generation.

Q248. Electric bulb life depends on:

(a) Filament thickness and voltage ✅

(b) Current only

(d) None

Explanation: Thicker filament lasts longer; overvoltage reduces life.

Q249. Electric lamp efficiency is measured by:

(a) Lumens per watt ✅

(b) Watts only

(d) None

Explanation: Indicates light output per unit power consumed.

Q250. Tungsten is preferred for filaments because:

(a) High melting point and durability ✅

(b) Low melting point

(d) None

Explanation: Can withstand high temperatures without melting, ensuring long life.

Q251. An electric cell converts:

(a) Chemical energy into electrical energy ✅

(b) Electrical energy into chemical energy

(d) None

Explanation: Electrochemical reactions inside the cell release electrons, producing current.

Q252. Primary cells are:

(a) Non-rechargeable ✅

(b) Rechargeable

(d) None

Explanation: Chemical reaction is irreversible. Examples: dry cell, voltaic cell.

Q253. Secondary cells are:

(a) Rechargeable ✅

(b) Non-rechargeable

(d) None

Explanation: Chemical reaction is reversible. Examples: lead-acid battery, lithium-ion.

Q254. EMF of a cell is:

(a) Work done per unit charge in moving it around circuit ✅

(b) Voltage across terminals always

(d) None

Explanation: EMF is maximum potential difference when no current flows.

Q255. Terminal voltage of cell is:

(a) V = E – Ir ✅

(b) V = E + Ir

(d) None

Explanation: Internal resistance reduces voltage available to external circuit.

Q256. Internal resistance of cell depends on:

(a) Distance between electrodes and electrolyte nature ✅

(b) Voltage only

(d) None

Explanation: Larger electrode separation and poor electrolyte increase internal resistance.

Q257. Dry cell is:

(a) Primary cell ✅

(b) Secondary cell

(d) None

Explanation: Non-rechargeable, commonly used in torches, radios.

Q258. Electrolyte in dry cell is:

(a) Paste of ammonium chloride and zinc chloride ✅

(b) Sulphuric acid

(d) None

Explanation: Provides medium for ion flow in dry cell.

Q259. Lead-acid battery is:

(a) Secondary cell ✅

(b) Primary cell

(d) None

Explanation: Rechargeable, widely used in automobiles.

Q260. Electrolyte in lead-acid battery is:

(a) Dilute sulphuric acid ✅

(b) Ammonium chloride

(d) None

Explanation: Provides ions for chemical reaction during charging/discharging.

Q261. Charging of battery means:

(a) Reversing chemical reaction ✅

(b) Using up electrolyte

(d) None

Explanation: External current restores original chemical composition.

Q262. Discharging of battery means:

(a) Chemical energy converted to electrical energy ✅

(b) Electrical energy converted to chemical energy

(d) None

Explanation: Normal operation of battery powering devices.

Q263. Capacity of battery is measured in:

(a) Ampere-hour (Ah) ✅

(b) Watt

(d) None

Explanation: Indicates total charge battery can deliver over time.

Q264. Lithium-ion battery is:

(a) Secondary cell ✅

(b) Primary cell

(d) None

Explanation: Rechargeable, widely used in mobiles and laptops.

Q265. Nickel-cadmium battery is:

(a) Secondary cell ✅

(b) Primary cell

(d) None

Explanation: Rechargeable, durable, used in portable electronics.

Q266. Fuel cell converts:

(a) Chemical energy of fuel directly into electrical energy ✅

(b) Electrical energy into chemical energy

(d) None

Explanation: Hydrogen-oxygen fuel cell produces electricity and water.

Q267. Internal resistance of cell increases with:

(a) Decrease in electrolyte concentration ✅

(b) Increase in electrode area

(d) None

Explanation: Poor electrolyte reduces ion mobility, increasing resistance.

Q268. EMF of cell depends on:

(a) Nature of electrodes and electrolyte ✅

(b) Size of cell

(d) None

Explanation: Determined by chemical composition, not size.

Q269. Grouping of cells in series increases:

(a) Voltage ✅

(b) Current

(d) None

Explanation: EMFs add up, giving higher total voltage.

Q270. Grouping of cells in parallel increases:

(a) Current capacity ✅

(b) Voltage

(d) None

Explanation: Current capacity increases, voltage remains same.

Q271. Polarization in cell is caused by:

(a) Accumulation of hydrogen gas on electrode ✅

(b) Increase in voltage

(d) None

Explanation: Hydrogen bubbles reduce effective electrode area, lowering efficiency.

Q272. Depolarizer in dry cell is:

(a) Manganese dioxide ✅

(b) Copper sulphate

(d) None

Explanation: Removes hydrogen bubbles, preventing polarization.

Q273. Button cells are:

(a) Small primary cells ✅

(b) Secondary cells

(d) None

Explanation: Compact, used in watches, calculators.

Q274. Solar cell converts:

(a) Light energy into electrical energy ✅

(b) Electrical energy into light

(d) None

Explanation: Photovoltaic effect generates electricity directly from sunlight.

Q275. Advantage of secondary cells over primary cells:

(a) Rechargeable, longer life ✅

(b) Non-rechargeable

(d) None

Explanation: Can be reused many times, economical in long term.

Q276. Household circuits are connected in:

(a) Parallel ✅

(b) Series

(d) None

Explanation: In parallel, each appliance gets full voltage and works independently. In series, one failure would stop the entire circuit.

Q277. Advantage of parallel connection in homes:

(a) Independent operation of appliances ✅

(b) Reduced voltage

(d) None

Explanation: Each device can be switched on/off without affecting others, and all receive rated voltage.

Q278. Disadvantage of series connection in homes:

(a) One appliance failure breaks circuit ✅

(b) Voltage increases

(d) None

Explanation: If one bulb fails in series, the entire circuit stops working.

Q279. Electric shock occurs due to:

(a) Current passing through body ✅

(b) Voltage only

(d) None

Explanation: Severity depends on current magnitude, duration, and path through body.

Q280. Safety device in household wiring:

(a) Fuse ✅

(b) Bulb

(d) None

Explanation: Fuse protects circuit from overload by melting and breaking connection.

Q281. Circuit breaker advantage over fuse:

(a) Reusable ✅

(b) Non-reusable

(d) None

Explanation: Breaker trips during overload but can be reset, unlike fuse which must be replaced.

Q282. Earthing in household wiring is done to:

(a) Prevent electric shock ✅

(b) Increase voltage

(d) None

Explanation: Provides safe path for leakage current to ground, protecting users.

Q283. Three-pin plug has:

(a) Live, neutral, earth ✅

(b) Two live wires

(d) None

Explanation: Earth pin is thicker and longer for safety.

Q284. Electric shock hazard is reduced by:

(a) Proper earthing ✅

(b) Removing fuse

(d) None

Explanation: Earthing ensures leakage current flows safely to ground.

Q285. Short circuit occurs when:

(a) Live and neutral wires touch ✅

(b) Live and earth wires touch

(d) None

Explanation: Causes sudden large current, dangerous for appliances.

Q286. Overloading occurs when:

(a) Too many appliances connected ✅

(b) Only one appliance connected

(d) None

Explanation: Excess current flows, heating wires and risking fire.

Q287. Electric shock severity depends on:

(a) Current magnitude ✅

(b) Voltage only

(d) None

Explanation: Even small currents (~50 mA) can be fatal if through heart.

Q288. Household supply in India is:

(a) 220 V, 50 Hz AC ✅

(b) 110 V, 60 Hz AC

(d) None

Explanation: Standard domestic supply in India is 220 volts alternating current.

Q289. Household supply in USA is:

(a) 110 V, 60 Hz AC ✅

(b) 220 V, 50 Hz AC

(d) None

Explanation: Standard domestic supply in USA is 110 volts alternating current.

Q290. Electric shock is more dangerous in:

(a) AC supply ✅

(b) DC supply

(d) None

Explanation: AC causes muscular contraction and fibrillation, making it harder to let go.

Q291. Resistance of human body is:

(a) 1000–10000 Ω ✅

(b) 1 Ω

(d) None

Explanation: Depends on moisture and contact area. Wet skin reduces resistance drastically.

Q292. Safe limit of current for human body:

(a) < 5 mA ✅

(b) 50 mA

(d) None

Explanation: Currents above 50 mA can be fatal. Safe limit is very low.

Q293. Lightning is:

(a) Discharge of atmospheric electricity ✅

(b) Discharge of magnetic energy

(d) None

Explanation: Huge potential difference between clouds and ground causes discharge.

Q294. Lightning conductor works on:

(a) Providing safe path to ground ✅

(b) Increasing voltage

(d) None

Explanation: Metal rod directs discharge safely into Earth.

Q295. Electric energy in transmission lines is reduced by:

(a) Using high voltage ✅

(b) Using low voltage

(d) None

Explanation: High voltage reduces current, minimizing I²R losses.

Q296. Electric appliances are rated in:

(a) Watts ✅

(b) Volts

(d) None

Explanation: Indicates power consumption per unit time.

Q297. Electric shock prevention device:

(a) Residual current device (RCD) ✅

(b) Bulb

(d) None

Explanation: Detects leakage current and disconnects supply instantly.

Q298. Household wiring uses:

(a) Copper wires ✅

(b) Aluminum wires

(d) None

Explanation: Copper has low resistivity and high conductivity, making it ideal.

Q299. Electric energy consumption depends on:

(a) Power × time ✅

(b) Voltage only

(d) None

Explanation: E = Pt. Higher power or longer usage increases

Q300. Electric shock can be avoided by:

(a) Proper insulation and earthing ✅

(b) Removing fuse

(d) None

Explanation: Insulation prevents contact, earthing provides safe discharge path.

Q301. If a 10 Ω resistor is connected across 20 V supply, current is:

(a) 2 A ✅

(b) 0.5 A

(d) None

Explanation: I = V/R = 20/10 = 2 A. Ohm’s law directly applied.

Q302. Power consumed by above resistor:

(a) 40 W ✅

(b) 20 W

(d) None

Explanation: P = VI = 20 × 2 = 40 W. Alternatively, P = V²/R = 400/10 = 40 W.

Q303. Two resistors 6 Ω and 3 Ω in series across 18 V supply, current is:

(a) 2 A ✅

(b) 3 A

(d) None

Explanation: R_total = 6 + 3 = 9 Ω. I = V/R = 18/9 = 2 A.

Q304. Voltage across 6 Ω resistor in above case:

(a) 12 V ✅

(b) 6 V

(d) None

Explanation: V = IR = 2 × 6 = 12 V. Voltage divides in series.

Q305. Two resistors 6 Ω and 3 Ω in parallel across 18 V supply, current is:

(a) 6 A ✅

(b) 2 A

(d) None

Explanation: R_total = (6×3)/(6+3) = 18/9 = 2 Ω. I = V/R = 18/2 = 9 A. Correction: Actually 9 A ✅.

Q306. Current through 6 Ω resistor in above parallel case:

(a) 3 A ✅

(b) 6 A

(d) None

Explanation: I = V/R = 18/6 = 3 A. Each branch current depends on its resistance.

Q307. Current through 3 Ω resistor in above parallel case:

(a) 6 A ✅

(b) 3 A

(d) None

Explanation: I = V/R = 18/3 = 6 A. Branch currents add to total 9 A.

Q308. A 100 W, 220 V bulb draws current:

(a) 0.45 A ✅

(b) 2 A

(d) None

Explanation: I = P/V = 100/220 ≈ 0.45 A.

Q309. Resistance of above bulb:

(a) 484 Ω ✅

(b) 220 Ω

(d) None

Explanation: R = V/I = 220/0.45 ≈ 484 Ω.

Q310. Energy consumed by 100 W bulb in 10 hours:

(a) 1 kWh ✅

(b) 10 kWh

(d) None

Explanation: E = Pt = 100 W × 10 h = 1000 Wh = 1 kWh.

Q311. A 60 W, 220 V bulb and 100 W, 220 V bulb connected in series, which glows brighter?

(a) 60 W bulb ✅

(b) 100 W bulb

(d) None

Explanation: In series, same current flows. Power ∝ resistance. 60 W bulb has higher resistance, dissipates more power.

Q312. Resistance of 60 W, 220 V bulb:

(a) 806 Ω ✅

(b) 484 Ω

(d) None

Explanation: R = V²/P = 220²/60 ≈ 806 Ω.

Q313. Resistance of 100 W, 220 V bulb:

(a) 484 Ω ✅

(b) 806 Ω

(d) None

Explanation: R = V²/P = 220²/100 ≈ 484 Ω.

Q314. In series, current through both bulbs:

(a) Same ✅

(b) Different

(d) None

Explanation: Series connection ensures equal current through all elements.

Q315. In parallel, voltage across both bulbs:

(a) Same ✅

(b) Different

(d) None

Explanation: Parallel connection ensures equal voltage across branches.

Q316. Household bulbs are connected in:

(a) Parallel ✅

(b) Series

(d) None

Explanation: Ensures each bulb gets full voltage and works independently.

Q317. A 2 kW heater used for 2 hours consumes energy:

(a) 4 kWh ✅

(b) 2 kWh

(d) None

Explanation: E = Pt = 2000 W × 2 h = 4000 Wh = 4 kWh.

Q318. Cost of above energy at ₹5 per kWh:

(a) ₹20 ✅

(b) ₹10

(d) None

Explanation: Cost = 4 × 5 = ₹20.

Q319. A 12 V battery supplies 6 A current for 10 minutes. Total charge delivered:

(a) 3600 C ✅

(b) 600 C

(d) None

Explanation: Q = It = 6 × (10 × 60) = 3600 C.

Q320. Energy delivered by above battery:

(a) 43.2 kJ ✅

(b) 12 kJ

(d) None

Explanation: W = VQ = 12 × 3600 = 43,200 J = 43.2 kJ.

Q321. A 10 Ω resistor carries 2 A current for 5 minutes. Heat produced:

(a) 1200 J ✅

(b) 2000 J

(d) None

Explanation: H = I²Rt = 4 × 10 × 300 = 12,000 J. Correction: Actually 12,000 J ✅.

Q322. A 220 V, 2 A appliance consumes power:

(a) 440 W ✅

(b) 220 W

(d) None

Explanation: P = VI = 220 × 2 = 440 W.

Q323. Energy consumed by above appliance in 5 hours:

(a) 2.2 kWh ✅

(b) 1.1 kWh

(d) None

Explanation: E = Pt = 440 × 5 h = 2200 Wh = 2.2 kWh.

Q324. Cost of above energy at ₹6 per kWh:

(a) ₹13.2 ✅

(b) ₹10

(d) None

Explanation: Cost = 2.2 × 6 = ₹13.2.

Q325. A 100 W bulb and 200 W bulb connected in parallel to 220 V supply, which consumes more current?

(a) 200 W bulb ✅

(b) 100 W bulb

(d) None

Explanation: I = P/V. For 200 W bulb, I = 200/220 ≈ 0.91 A. For 100 W bulb, I = 100/220 ≈ 0.45 A. Hence 200 W bulb draws more current.

Q326. A wire of resistance 10 Ω is doubled in length. New resistance is:

(a) 40 Ω ✅

(b) 20 Ω

(d) None

Explanation: Resistance ∝ L²/A when volume constant. Doubling length doubles L, halves area, so R_new = 4R = 40 Ω.

Q327. Resistance of wire is halved when:

(a) Area is doubled ✅

(b) Length doubled

(d) None

Explanation: R = ρL/A. Increasing area reduces resistance proportionally.

Q328. A 100 W, 220 V bulb has resistance:

(a) 484 Ω ✅

(b) 220 Ω

(d) None

Explanation: R = V²/P = 220²/100 ≈ 484 Ω.

Q329. A 60 W, 220 V bulb has resistance:

(a) 806 Ω ✅

(b) 484 Ω

(d) None

Explanation: R = V²/P = 220²/60 ≈ 806 Ω.

Q330. Which bulb glows brighter in series: 60 W or 100 W?

(a) 60 W ✅

(b) 100 W

(d) None

Explanation: In series, same current flows. Power ∝ resistance. Higher resistance bulb (60 W) dissipates more power.

Q331. In parallel, which bulb glows brighter: 60 W or 100 W?

(a) 100 W ✅

(b) 60 W

(d) None

Explanation: In parallel, both get full voltage. Higher wattage bulb consumes more power, glows brighter.

Q332. A 2 kW heater used for 3 hours consumes energy:

(a) 6 kWh ✅

(b) 2 kWh

(d) None

Explanation: E = Pt = 2000 W × 3 h = 6000 Wh = 6 kWh.

Q333. Cost of above energy at ₹5 per kWh:

(a) ₹30 ✅

(b) ₹20

(d) None

Explanation: Cost = 6 × 5 = ₹30.

Q334. A 220 V, 2 A fan consumes power:

(a) 440 W ✅

(b) 220 W

(d) None

Explanation: P = VI = 220 × 2 = 440 W.

Q335. Energy consumed by above fan in 10 hours:

(a) 4.4 kWh ✅

(b) 2.2 kWh

(d) None

Explanation: E = Pt = 440 × 10 h = 4400 Wh = 4.4 kWh.

Q336. Cost of above energy at ₹6 per kWh:

(a) ₹26.4 ✅

(b) ₹20

(d) None

Explanation: Cost = 4.4 × 6 = ₹26.4.

Q337. A 12 V battery supplies 3 A current for 30 minutes. Charge delivered:

(a) 5400 C ✅

(b) 3600 C

(d) None

Explanation: Q = It = 3 × (30 × 60) = 5400 C.

Q338. Energy delivered by above battery:

(a) 64.8 kJ ✅

(b) 43.2 kJ

(d) None

Explanation: W = VQ = 12 × 5400 = 64,800 J = 64.8 kJ.

Q339. A 5 Ω resistor carries 4 A current for 2 minutes. Heat produced:

(a) 9600 J ✅

(b) 4800 J

(d) None

Explanation: H = I²Rt = 16 × 5 × 120 = 9600 J.

Q340. A 220 V, 100 W bulb used for 5 hours consumes energy:

(a) 0.5 kWh ✅

(b) 1 kWh

(d) None

Explanation: E = Pt = 100 × 5 h = 500 Wh = 0.5 kWh.

Q341. Cost of above energy at ₹8 per kWh:

(a) ₹4 ✅

(b) ₹8

(d) None

Explanation: Cost = 0.5 × 8 = ₹4.

Q342. A 60 W bulb and 100 W bulb connected in parallel to 220 V supply, total power consumed:

(a) 160 W ✅

(b) 100 W

(d) None

Explanation: In parallel, both get full voltage. Total = 60 + 100 = 160 W.

Q343. A 60 W bulb and 100 W bulb connected in series to 220 V supply, total power consumed:

(a) Less than 160 W ✅

(b) 160 W

(d) None

Explanation: In series, current is same, voltage divides. Power is less than sum of ratings.

Q344. Resistance of 200 W, 220 V bulb:

(a) 242 Ω ✅

(b) 484 Ω

(d) None

Explanation: R = V²/P = 220²/200 ≈ 242 Ω.

Q345. Resistance of 40 W, 220 V bulb:

(a) 1210 Ω ✅

(b) 484 Ω

(d) None

Explanation: R = V²/P = 220²/40 ≈ 1210 Ω.

Q346. Which bulb has thicker filament: 40 W or 100 W?

(a) 100 W ✅

(b) 40 W

(d) None

Explanation: Lower resistance (100 W bulb) means thicker filament to allow more current.

Q347. Which bulb has thinner filament: 40 W or 100 W?

(a) 40 W ✅

(b) 100 W

(d) None

Explanation: Higher resistance (40 W bulb) means thinner filament to restrict current.

Q348. A 220 V, 2 kW geyser used for 1 hour consumes energy:

(a) 2 kWh ✅

(b) 1 kWh

(d) None

Explanation: E = Pt = 2000 W × 1 h = 2000 Wh = 2 kWh.

Q349. Cost of above energy at ₹7 per kWh:

(a) ₹14 ✅

(b) ₹7

(d) None

Explanation: Cost = 2 × 7 = ₹14.

Q350. A 220 V, 500 W heater used for 4 hours consumes energy:

(a) 2 kWh ✅

(b) 1 kWh

(d) None

Explanation: E = Pt = 500 × 4 h = 2000 Wh = 2 kWh.

Q351. Power transmission lines use:

(a) High voltage ✅

(b) Low voltage

(d) None

Explanation: High voltage reduces current for same power, minimizing I²R losses in long-distance transmission.

Q352. Power loss in transmission lines is:

(a) P_loss = I²R ✅

(b) P_loss = IR

(d) None

Explanation: Loss depends on square of current and resistance of wires. Reducing current reduces loss.

Q353. Step-up transformer is used in transmission to:

(a) Increase voltage, reduce current ✅

(b) Decrease voltage, increase current

(d) None

Explanation: Higher voltage reduces current, minimizing losses.

Q354. Step-down transformer is used at consumer end to:

(a) Reduce voltage to safe level ✅

(b) Increase voltage

(d) None

Explanation: Household appliances require lower voltage (220 V in India).

Q355. Household supply in India is:

(a) 220 V, 50 Hz AC ✅

(b) 110 V, 60 Hz AC

(d) None

Explanation: Standard domestic supply in India is 220 volts alternating current.

Q356. Household supply in USA is:

(a) 110 V, 60 Hz AC ✅

(b) 220 V, 50 Hz AC

(d) None

Explanation: Standard domestic supply in USA is 110 volts alternating current.

Q357. Earthing in household wiring is done to:

(a) Prevent electric shock ✅

(b) Increase voltage

(d) None

Explanation: Provides safe path for leakage current to ground, protecting users.

Q358. Fuse wire is made of:

(a) Tin-lead alloy ✅

(b) Copper

(d) None

Explanation: Low melting point ensures quick response to overload.

Q359. Circuit breaker advantage over fuse:

(a) Reusable ✅

(b) Non-reusable

(d) None

Explanation: Breaker trips during overload but can be reset, unlike fuse which must be replaced.

Q360. Residual current device (RCD) detects:

(a) Leakage current ✅

(b) Voltage only

(d) None

Explanation: Disconnects supply instantly when leakage current is detected, preventing shock.

Q361. Lightning is:

(a) Discharge of atmospheric electricity ✅

(b) Discharge of magnetic energy

(d) None

Explanation: Huge potential difference between clouds and ground causes discharge.

Q362. Lightning conductor works on:

(a) Providing safe path to ground ✅

(b) Increasing voltage

(d) None

Explanation: Metal rod directs discharge safely into Earth.

Q363. Electric shock occurs due to:

(a) Current passing through body ✅

(b) Voltage only

(d) None

Explanation: Severity depends on current magnitude, duration, and path through body.

Q364. Safe limit of current for human body:

(a) < 5 mA ✅

(b) 50 mA

(d) None

Explanation: Currents above 50 mA can be fatal. Safe limit is very low.

Q365. Resistance of human body is:

(a) 1000–10000 Ω ✅

(b) 1 Ω

(d) None

Explanation: Depends on moisture and contact area. Wet skin reduces resistance drastically.

Q366. Electric shock is more dangerous in:

(a) AC supply ✅

(b) DC supply

(d) None

Explanation: AC causes muscular contraction and fibrillation, making it harder to let go.

Q367. Overloading occurs when:

(a) Too many appliances connected ✅

(b) Only one appliance connected

(d) None

Explanation: Excess current flows, heating wires and risking fire.

Q368. Short circuit occurs when:

(a) Live and neutral wires touch ✅

(b) Live and earth wires touch

(d) None

Explanation: Causes sudden large current, dangerous for appliances.

Q369. Three-pin plug has:

(a) Live, neutral, earth ✅

(b) Two live wires

(d) None

Explanation: Earth pin is thicker and longer for safety.

Q370. Earthing ensures:

(a) Leakage current flows safely to ground ✅

(b) Voltage increases

(d) None

Explanation: Protects user from shock by diverting current.

Q371. Electric appliances are rated in:

(a) Watts ✅

(b) Volts

(d) None

Explanation: Indicates power consumption per unit time.

Q372. Electric energy consumption depends on:

(a) Power × time ✅

(b) Voltage only

(d) None

Explanation: E = Pt. Higher power or longer usage increases consumption.

Q373. Electric shock prevention device:

(a) Residual current device (RCD) ✅

(b) Bulb

(d) None

Explanation: Detects leakage current and disconnects supply instantly.

Q374. Household wiring uses:

(a) Copper wires ✅

(b) Aluminum wires

(d) None

Explanation: Copper has low resistivity and high conductivity, making it ideal.

Q375. Electric energy in transmission lines is reduced by:

(a) Using high voltage ✅

(b) Using low voltage

(d) None

Explanation: High voltage reduces current, minimizing I²R losses.

Q376. Alternating current (AC) is preferred for transmission because:

(a) Easy to transform voltage levels ✅

(b) Less dangerous

(d) None

Explanation: Transformers work only with AC, allowing efficient step-up and step-down of voltage for transmission and usage.

Q377. Direct current (DC) is mainly used in:

(a) Batteries and electronic devices ✅

(b) Transmission lines

(d) None

Explanation: DC provides steady voltage, ideal for electronics, but not efficient for long-distance transmission.

Q378. Frequency of AC in India is:

(a) 50 Hz ✅

(b) 60 Hz

(d) None

Explanation: AC completes 50 cycles per second in India.

Q379. Frequency of AC in USA is:

(a) 60 Hz ✅

(b) 50 Hz

(d) None

Explanation: Standard domestic supply in USA is 60 cycles per second.

Q380. RMS value of AC is:

(a) Effective value producing same heating as DC ✅

(b) Peak value

(d) None

Explanation: RMS = V₀/√2. Represents equivalent DC value for heating effect.

Q381. Average value of AC over half cycle:

(a) 0.637 V₀ ✅

(b) 0.707 V₀

(d) None

Explanation: Derived from integration of sine wave over half cycle.

Q382. Peak value of AC is:

(a) Maximum instantaneous value ✅

(b) RMS value

(d) None

Explanation: Denoted by V₀ or I₀. Occurs at crest of sine wave.

Q383. Relation between RMS and peak value:

(a) V_rms = V₀/√2 ✅

(b) V_rms = V₀

(d) None

Explanation: Effective value is 0.707 times peak value.

Q384. Power in pure resistive AC circuit:

(a) P = VI ✅

(b) P = 0

(d) None

Explanation: Voltage and current are in phase, so power factor = 1.

Q385. Power in pure inductive AC circuit:

(a) Zero ✅

(b) Maximum

(d) None

Explanation: Voltage leads current by 90°, average power = 0.

Q386. Power in pure capacitive AC circuit:

(a) Zero ✅

(b) Maximum

(d) None

Explanation: Current leads voltage by 90°, average power = 0.

Q387. Power factor is defined as:

(a) cos φ ✅

(b) sin φ

(d) None

Explanation: φ is phase angle between voltage and current. Determines efficiency.

Q388. Leading power factor occurs in:

(a) Capacitive circuits ✅

(b) Inductive circuits

(d) None

Explanation: Current leads voltage in capacitive load.

Q389. Lagging power factor occurs in:

(a) Inductive circuits ✅

(b) Capacitive circuits

(d) None

Explanation: Current lags voltage in inductive load.

Q390. Apparent power is:

(a) Product of RMS voltage and current ✅

(b) Real power

(d) None

Explanation: S = VI. Measured in volt-ampere (VA).

Q391. Real power is:

(a) P = VI cos φ ✅

(b) P = VI

(d) None

Explanation: Portion of power actually consumed or converted into work.

Q392. Reactive power is:

(a) Q = VI sin φ ✅

(b) Q = VI cos φ

(d) None

Explanation: Represents energy alternately stored and released by inductors/capacitors.

Q393. Transformer efficiency is maximum when:

(a) Copper loss = iron loss ✅

(b) Copper loss > iron loss

(d) None

Explanation: Condition for maximum efficiency is equal copper and iron losses.

Q394. Copper loss in transformer is:

(a) I²R loss in windings ✅

(b) Hysteresis loss

(d) None

Explanation: Resistance of coils causes heating when current flows.

Q395. Iron loss in transformer is due to:

(a) Hysteresis and eddy currents ✅

(b) Copper resistance

(d) None

Explanation: Alternating flux in core causes energy loss.

Q396. Laminated core reduces:

(a) Eddy current loss ✅

(b) Copper loss

(d) None

Explanation: Thin laminations increase resistance to eddy currents, minimizing loss.

Q397. Household appliances use:

(a) Step-down transformers ✅

(b) Step-up transformers

(d) None

Explanation: Reduce voltage to safe levels for domestic use.

Q398. High voltage transmission reduces:

(a) Current ✅

(b) Voltage

(d) None

Explanation: For same power, higher voltage means lower current, reducing losses.

Q399. Electric motor works on:

(a) Magnetic effect of current ✅

(b) Heating effect

(d) None

Explanation: Current in coil produces torque in magnetic field, converting electrical energy to mechanical.

Q400. Electric generator works on:

(a) Electromagnetic induction ✅

(b) Heating effect

(d) None

Explanation: Converts mechanical energy into electrical energy by rotating coil in magnetic field.

Q401. Magnetic effect of current was discovered by:

(a) Oersted ✅

(b) Faraday

(d) None

Explanation: Oersted observed that a current-carrying wire deflects a nearby compass needle, proving link between electricity and magnetism.

Q402. Magnetic field around straight conductor is:

(a) Concentric circles ✅

(b) Straight lines

(d) None

Explanation: Field lines form concentric circles around wire, direction given by right-hand thumb rule.

Q403. Right-hand thumb rule states:

(a) Thumb points current, fingers show field ✅

(b) Thumb points field, fingers show current

(d) None

Explanation: If thumb points in direction of current, curled fingers show magnetic field direction.

Q404. Magnetic field inside solenoid is:

(a) Uniform ✅

(b) Non-uniform

(d) None

Explanation: Field lines inside solenoid are parallel and equally spaced, showing uniform field.

Q405. Magnetic field strength inside solenoid depends on:

(a) Number of turns, current, length ✅

(b) Voltage only

(d) None

Explanation: B = μ₀nI. More turns and current increase field strength.

Q406. Electromagnet is made by:

(a) Current through solenoid with iron core ✅

(b) Permanent magnet

(d) None

Explanation: Iron core enhances magnetic field, making strong electromagnet.

Q407. Strength of electromagnet increases with:

(a) Current and number of turns ✅

(b) Voltage only

(d) None

Explanation: More current and turns produce stronger magnetic field.

Q408. Magnetic field due to circular loop is:

(a) Stronger at center ✅

(b) Stronger at edges

(d) None

Explanation: Field lines are concentrated at center, giving maximum strength.

Q409. Magnetic field due to solenoid resembles:

(a) Bar magnet ✅

(b) Circular loop

(d) None

Explanation: Solenoid produces uniform field inside, similar to bar magnet with poles.

Q410. Fleming’s left-hand rule is used for:

(a) Direction of force on conductor ✅

(b) Direction of current

(d) None

Explanation: Thumb = force, forefinger = field, middle finger = current.

Q411. Force on current-carrying conductor in magnetic field:

(a) F = BIL sin θ ✅

(b) F = BIL

(d) None

Explanation: Depends on field strength, current, length, and angle between conductor and field.

Q412. Electric motor works on:

(a) Magnetic effect of current ✅

(b) Heating effect

(d) None

Explanation: Current in coil produces torque in magnetic field, converting electrical energy to mechanical.

Q413. Electric generator works on:

(a) Electromagnetic induction ✅

(b) Heating effect

(d) None

Explanation: Converts mechanical energy into electrical energy by rotating coil in magnetic field.

Q414. Electromagnetic induction was discovered by:

(a) Faraday ✅

(b) Oersted

(d) None

Explanation: Faraday showed that changing magnetic flux induces current in conductor.

Q415. Lenz’s law states:

(a) Induced current opposes cause ✅

(b) Induced current aids cause

(d) None

Explanation: Induced current direction always opposes change in flux, conserving energy.

Q416. Fleming’s right-hand rule is used for:

(a) Direction of induced current ✅

(b) Direction of force

(d) None

Explanation: Thumb = motion, forefinger = field, middle finger = induced current.

Q417. Self-induction is:

(a) Induced emf in coil due to change in its own current ✅

(b) Induced emf due to external coil

(d) None

Explanation: Coil resists change in current by inducing emf in itself.

Q418. Mutual induction is:

(a) Induced emf in one coil due to change in current in another ✅

(b) Induced emf in same coil

(d) None

Explanation: Basis of transformer operation.

Q419. Inductance unit is:

(a) Henry ✅

(b) Ohm

(d) None

Explanation: 1 Henry = 1 V induced when current changes at 1 A/s.

Q420. Energy stored in inductor:

(a) U = ½ LI² ✅

(b) U = LI²

(d) None

Explanation: Energy stored in magnetic field of inductor.

Q421. Eddy currents are:

(a) Currents induced in bulk conductor ✅

(b) Currents in thin wire

(d) None

Explanation: Circular currents in conductor due to changing magnetic flux, causing energy loss.

Q422. Eddy current losses reduced by:

(a) Laminated core ✅

(b) Solid core

(d) None

Explanation: Laminations increase resistance, reducing eddy currents.

Q423. Transformer works on:

(a) Mutual induction ✅

(b) Self-induction

(d) None

Explanation: Transfers energy between coils via changing magnetic flux.

Q424. DC motor works on:

(a) Magnetic effect of current ✅

(b) Heating effect

(d) None

Explanation: Current in coil produces torque in magnetic field, converting DC electrical energy to mechanical.

Q425. AC generator works on:

(a) Electromagnetic induction ✅

(b) Heating effect

(d) None

Explanation: Rotating coil in magnetic field induces alternating current.

Q426. Electromagnetic waves were discovered by:

(a) Hertz ✅

(b) Maxwell

(d) None

Explanation: Heinrich Hertz experimentally proved existence of electromagnetic waves predicted by Maxwell.

Q427. Electromagnetic waves are:

(a) Transverse ✅

(b) Longitudinal

(d) None

Explanation: Electric and magnetic fields oscillate perpendicular to each other and to direction of propagation.

Q428. Speed of electromagnetic waves in vacuum:

(a) 3 × 10⁸ m/s ✅

(b) 3 × 10⁶ m/s

(d) None

Explanation: Same as speed of light. c = 1/√(μ₀ε₀).

Q429. Electromagnetic spectrum is arranged according to:

(a) Frequency or wavelength ✅

(b) Voltage

(d) None

Explanation: Spectrum ranges from radio waves to gamma rays, ordered by frequency/wavelength.

Q430. Radio waves are used in:

(a) Communication ✅

(b) Cooking

(d) None

Explanation: Long wavelength, low frequency waves ideal for broadcasting.

Q431. Microwaves are used in:

(a) Radar and cooking ✅

(b) X-ray imaging

(d) None

Explanation: Microwaves heat food and are used in radar systems.

Q432. Infrared waves are used in:

(a) Remote controls and thermal imaging ✅

(b) X-rays

(d) None

Explanation: Infrared radiation is emitted by hot bodies, used in sensors and remotes.

Q433. Visible light range is:

(a) 400–700 nm ✅

(b) 200–400 nm

(d) None

Explanation: Human eye detects electromagnetic waves in this wavelength range.

Q434. Ultraviolet rays are used in:

(a) Sterilization ✅

(b) Cooking

(d) None

Explanation: UV kills bacteria, used in medical sterilization.

Q435. X-rays are used in:

(a) Medical imaging ✅

(b) Cooking

(d) None

Explanation: High energy rays penetrate tissues, used in radiography.

Q436. Gamma rays are used in:

(a) Cancer treatment ✅

(b) Cooking

(d) None

Explanation: Very high energy rays destroy cancer cells.

Q437. Electromagnetic waves are produced by:

(a) Accelerated charges ✅

(b) Stationary charges

(d) None

Explanation: Changing electric field produces magnetic field and vice versa, propagating as waves.

Q438. Communication system requires:

(a) Transmitter, channel, receiver ✅

(b) Only transmitter

(d) None

Explanation: Complete system includes source, medium, and destination.

Q439. Modulation is:

(a) Superimposing information signal on carrier wave ✅

(b) Removing carrier wave

(d) None

Explanation: Enables transmission of low-frequency signals over long distances.

Q440. Types of modulation include:

(a) AM, FM, PM ✅

(b) AC, DC

(d) None

Explanation: Amplitude, frequency, and phase modulation are common techniques.

Q441. Demodulation is:

(a) Extracting information from carrier wave ✅

(b) Adding carrier wave

(d) None

Explanation: Receiver recovers original signal from modulated wave.

Q442. Antenna is used to:

(a) Transmit or receive electromagnetic waves ✅

(b) Store energy

(d) None

Explanation: Converts electrical signals into electromagnetic waves and vice versa.

Q443. Bandwidth of communication channel is:

(a) Range of frequencies transmitted ✅

(b) Voltage range

(d) None

Explanation: Determines data capacity of channel.

Q444. Satellite communication uses:

(a) Microwaves ✅

(b) Radio waves

(d) None

Explanation: Microwaves penetrate atmosphere and are used for satellite links.

Q445. Optical fiber communication uses:

(a) Light waves ✅

(b) Radio waves

(d) None

Explanation: Light signals travel through fiber with minimal loss, enabling high-speed data transfer.

Q446. Advantage of optical fiber:

(a) High bandwidth and low loss ✅

(b) High loss

(d) None

Explanation: Optical fibers provide fast, reliable communication.

Q447. Mobile communication uses:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Mobile phones transmit and receive signals using radio frequencies.

Q448. Television broadcasting uses:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Audio and video signals transmitted via radio waves.

Q449. Internet data transfer uses:

(a) Optical fiber and radio waves ✅

(b) Gamma rays

(d) None

Explanation: Combination of fiber optics and wireless signals enables global connectivity.

Q450. Radar works on:

(a) Reflection of microwaves ✅

(b) Reflection of radio waves

(d) None

Explanation: Radar detects objects by sending microwaves and analyzing reflected signals.

Q451. Photoelectric effect was explained by:

(a) Einstein ✅

(b) Planck

(d) None

Explanation: Einstein proposed that light consists of photons. Each photon transfers energy to an electron, ejecting it from metal surface.

Q452. Photoelectric effect proves:

(a) Particle nature of light ✅

(b) Wave nature of light

(d) None

Explanation: Only photons with sufficient energy can eject electrons, showing quantized particle behavior.

Q453. Work function is:

(a) Minimum energy required to eject electron ✅

(b) Maximum energy of photon

(d) None

Explanation: Depends on material. Measured in electron volts (eV).

Q454. Threshold frequency is:

(a) Minimum frequency of light to eject electron ✅

(b) Maximum frequency

(d) None

Explanation: f₀ = W/h. Below this frequency, no electrons are emitted regardless of intensity.

Q455. Energy of photon is:

(a) E = hf ✅

(b) E = h/f

(d) None

Explanation: Planck’s relation. h = Planck’s constant, f = frequency.

Q456. Kinetic energy of photoelectron is:

(a) KE = hf – W ✅

(b) KE = hf + W

(d) None

Explanation: Photon energy minus work function gives electron’s kinetic energy.

Q457. Stopping potential is:

(a) Potential required to stop photoelectrons ✅

(b) Potential to accelerate electrons

(d) None

Explanation: eV₀ = KE_max. Used to measure maximum kinetic energy.

Q458. Photoelectric current depends on:

(a) Intensity of light ✅

(b) Frequency only

(d) None

Explanation: More photons → more electrons emitted → higher current.

Q459. Photoelectric effect is instantaneous because:

(a) Photon transfers energy directly ✅

(b) Photon stores energy

(d) None

Explanation: No time lag between light incidence and electron emission.

Q460. Bohr’s atomic model explains:

(a) Hydrogen spectrum ✅

(b) Helium spectrum

(d) None

Explanation: Quantized orbits explain discrete spectral lines of hydrogen.

Q461. Energy levels in Bohr’s model are:

(a) Quantized ✅

(b) Continuous

(d) None

Explanation: Electrons occupy discrete energy states. Transition causes emission/absorption of photons.

Q462. Radius of nth orbit in hydrogen atom:

(a) rₙ = n²a₀ ✅

(b) rₙ = na₀

(d) None

Explanation: a₀ = Bohr radius ≈ 0.53 Å. Radius increases with n².

Q463. Energy of nth orbit in hydrogen atom:

(a) Eₙ = –13.6/n² eV ✅

(b) Eₙ = –13.6n² eV

(d) None

Explanation: Negative sign shows bound state. Energy decreases with increasing n.

Q464. Transition from higher to lower orbit emits:

(a) Photon ✅

(b) Electron

(d) None

Explanation: Energy difference released as photon of specific frequency.

Q465. Ionization energy of hydrogen atom:

(a) 13.6 eV ✅

(b) 10.2 eV

(d) None

Explanation: Energy required to remove electron from ground state.

Q466. Nuclear model of atom was proposed by:

(a) Rutherford ✅

(b) Bohr

(d) None

Explanation: Alpha particle scattering experiment showed nucleus at center.

Q467. Rutherford’s model failed to explain:

(a) Stability of atom ✅

(b) Existence of nucleus

(d) None

Explanation: Electrons should spiral into nucleus due to radiation, but atoms are stable.

Q468. Mass number is:

(a) Sum of protons and neutrons ✅

(b) Number of protons only

(d) None

Explanation: A = Z + N. Z = atomic number, N = neutrons.

Q469. Isotopes are:

(a) Same Z, different A ✅

(b) Same A, different Z

(d) None

Explanation: Same element with different neutron numbers.

Q470. Isobars are:

(a) Same A, different Z ✅

(b) Same Z, different A

(d) None

Explanation: Different elements with same mass number.

Q471. Isotones are:

(a) Same number of neutrons ✅

(b) Same number of protons

(d) None

Explanation: Different elements with equal neutron count.

Q472. Radioactivity was discovered by:

(a) Becquerel ✅

(b) Curie

(d) None

Explanation: Becquerel observed spontaneous emission from uranium salts.

Q473. Alpha particle is:

(a) Helium nucleus (2p, 2n) ✅

(b) Electron

(d) None

Explanation: α = ⁴He²⁺. Heavy, positively charged particle.

Q474. Beta particle is:

(a) Electron or positron ✅

(b) Proton

(d) None

Explanation: β⁻ = electron, β⁺ = positron emitted during decay.

Q475. Gamma radiation is:

(a) High-energy electromagnetic radiation ✅

(b) Proton emission

(d) None

Explanation: Emitted when nucleus de-excites. Very penetrating.

Q476. Nuclear fission is:

(a) Splitting of heavy nucleus into smaller nuclei ✅

(b) Combining of light nuclei

(d) None

Explanation: Heavy nuclei like U-235 split into smaller nuclei, releasing large energy.

Q477. Nuclear fusion is:

(a) Combining of light nuclei into heavier nucleus ✅

(b) Splitting of heavy nucleus

(d) None

Explanation: Hydrogen nuclei combine to form helium, releasing enormous energy.

Q478. Energy released in nuclear reactions is due to:

(a) Mass defect ✅

(b) Voltage

(d) None

Explanation: Δm converted to energy by Einstein’s relation E = Δmc².

Q479. Binding energy is:

(a) Energy required to break nucleus into nucleons ✅

(b) Energy to combine nucleons

(d) None

Explanation: Indicates stability of nucleus. Higher binding energy = more stable.

Q480. Binding energy per nucleon is maximum for:

(a) Iron (Fe) ✅

(b) Uranium

(d) None

Explanation: Iron nucleus is most stable, explaining why fusion of light and fission of heavy nuclei release energy.

Q481. Chain reaction occurs in:

(a) Nuclear fission ✅

(b) Nuclear fusion

(d) None

Explanation: Neutrons released in fission cause further fission, sustaining reaction.

Q482. Controlled chain reaction is used in:

(a) Nuclear reactor ✅

(b) Atomic bomb

(d) None

Explanation: Moderators and control rods regulate reaction rate for safe energy production.

Q483. Uncontrolled chain reaction occurs in:

(a) Atomic bomb ✅

(b) Nuclear reactor

(d) None

Explanation: Rapid fission releases massive destructive energy.

Q484. Moderator in nuclear reactor is:

(a) Slows down neutrons ✅

(b) Absorbs neutrons

(d) None

Explanation: Materials like graphite or heavy water slow neutrons for effective fission.

Q485. Control rods in nuclear reactor:

(a) Absorb excess neutrons ✅

(b) Slow neutrons

(d) None

Explanation: Made of cadmium or boron, they regulate chain reaction.

Q486. Coolant in nuclear reactor:

(a) Removes heat ✅

(b) Absorbs neutrons

(d) None

Explanation: Transfers heat from reactor core to turbines for electricity generation.

Q487. Nuclear fusion requires:

(a) Very high temperature and pressure ✅

(b) Low temperature

(d) None

Explanation: Overcomes repulsion between nuclei. Occurs in stars like the Sun.

Q488. Sun’s energy is due to:

(a) Nuclear fusion ✅

(b) Nuclear fission

(d) None

Explanation: Hydrogen nuclei fuse to form helium, releasing energy.

Q489. Hydrogen bomb works on:

(a) Nuclear fusion ✅

(b) Nuclear fission

(d) None

Explanation: Fusion of hydrogen isotopes releases enormous destructive energy.

Q490. Atomic bomb works on:

(a) Nuclear fission ✅

(b) Nuclear fusion

(d) None

Explanation: Uncontrolled fission of uranium or plutonium releases massive energy.

Q491. Nuclear reactor produces:

(a) Electricity ✅

(b) Light only

(d) None

Explanation: Heat from fission generates steam, driving turbines to produce electricity.

Q492. Nuclear fuel commonly used:

(a) Uranium-235, Plutonium-239 ✅

(b) Iron

(d) None

Explanation: These isotopes undergo fission easily, releasing energy.

Q493. Fusion reaction fuel:

(a) Isotopes of hydrogen (deuterium, tritium) ✅

(b) Uranium

(d) None

Explanation: Light nuclei combine to form helium, releasing energy.

Q494. Advantage of fusion over fission:

(a) More energy, less radioactive waste ✅

(b) Less energy, more waste

(d) None

Explanation: Fusion is cleaner and produces more energy per unit mass.

Q495. Disadvantage of fusion:

(a) Requires extremely high temperature ✅

(b) Produces radioactive waste

(d) None

Explanation: Difficult to achieve controlled fusion on Earth.

Q496. Nuclear power plants use:

(a) Controlled fission ✅

(b) Controlled fusion

(d) None

Explanation: Fission reactors are practical and widely used for electricity.

Q497. Nuclear fusion occurs naturally in:

(a) Stars ✅

(b) Earth’s core

(d) None

Explanation: Fusion powers stars, including the Sun.

Q498. Mass defect is:

(a) Difference between mass of nucleus and sum of nucleons ✅

(b) Sum of nucleons

(d) None

Explanation: Δm converted into binding energy.

Q499. Einstein’s mass-energy relation is:

(a) E = mc² ✅

(b) E = m/c²

(d) None

Explanation: Shows equivalence of mass and energy.

Q500. Nuclear energy is:

(a) Energy released due to nuclear reactions ✅

(b) Energy released due to chemical reactions

(d) None

Explanation: Fission and fusion reactions release enormous energy due to mass defect.

Q501. Semiconductor materials are:

(a) Silicon and germanium ✅

(b) Copper and aluminum

(d) None

Explanation: Semiconductors have conductivity between conductors and insulators. Silicon and germanium are most widely used.

Q502. Intrinsic semiconductor is:

(a) Pure semiconductor ✅

(b) Doped semiconductor

(d) None

Explanation: Contains no impurities. Conductivity depends only on temperature.

Q503. Extrinsic semiconductor is:

(a) Doped semiconductor ✅

(b) Pure semiconductor

(d) None

Explanation: Doping with impurities increases conductivity. Types: n-type and p-type.

Q504. N-type semiconductor is doped with:

(a) Pentavalent impurity ✅

(b) Trivalent impurity

(d) None

Explanation: Extra electrons increase conductivity. Example: phosphorus in silicon.

Q505. P-type semiconductor is doped with:

(a) Trivalent impurity ✅

(b) Pentavalent impurity

(d) None

Explanation: Creates holes as majority carriers. Example: boron in silicon.

Q506. Majority carriers in n-type semiconductor:

(a) Electrons ✅

(b) Holes

(d) None

Explanation: Extra electrons from pentavalent doping dominate conduction.

Q507. Majority carriers in p-type semiconductor:

(a) Holes ✅

(b) Electrons

(d) None

Explanation: Deficiency of electrons creates holes as majority carriers.

Q508. PN junction diode allows current:

(a) In forward bias ✅

(b) In reverse bias

(d) None

Explanation: Forward bias reduces barrier, allowing current flow. Reverse bias blocks current.

Q509. In reverse bias, diode current is:

(a) Very small (leakage current) ✅

(b) Very large

(d) None

Explanation: Only a tiny leakage current flows due to minority carriers.

Q510. Diode is used as:

(a) Rectifier ✅

(b) Amplifier

(d) None

Explanation: Converts AC into DC by allowing current only in one direction.

Q511. Half-wave rectifier uses:

(a) One diode ✅

(b) Two diodes

(d) None

Explanation: Allows current during one half cycle of AC.

Q512. Full-wave rectifier uses:

(a) Two or four diodes ✅

(b) One diode

(d) None

Explanation: Converts both half cycles of AC into DC.

Q513. Zener diode is used as:

(a) Voltage regulator ✅

(b) Amplifier

(d) None

Explanation: Operates in reverse breakdown region to maintain constant voltage.

Q514. LED stands for:

(a) Light Emitting Diode ✅

(b) Low Energy Device

(d) None

Explanation: Emits light when forward biased due to recombination of electrons and holes.

Q515. Photodiode works on:

(a) Photoelectric effect ✅

(b) Heating effect

(d) None

Explanation: Generates current when exposed to light. Used in sensors.

Q516. Transistor is made of:

(a) Two PN junctions ✅

(b) One PN junction

(d) None

Explanation: Combination of three layers: NPN or PNP.

Q517. Transistor has:

(a) Three terminals: emitter, base, collector ✅

(b) Two terminals

(d) None

Explanation: Emitter injects carriers, base controls, collector collects carriers.

Q518. In NPN transistor, majority carriers are:

(a) Electrons ✅

(b) Holes

(d) None

Explanation: N-type regions dominate, so electrons are majority carriers.

Q519. In PNP transistor, majority carriers are:

(a) Holes ✅

(b) Electrons

(d) None

Explanation: P-type regions dominate, so holes are majority carriers.

Q520. Transistor is used as:

(a) Amplifier and switch ✅

(b) Rectifier only

(d) None

Explanation: Amplifies weak signals and acts as electronic switch.

Q521. Common base transistor configuration has:

(a) Low input resistance, high output resistance ✅

(b) High input resistance, low output resistance

(d) None

Explanation: Input between emitter-base, output between collector-base.

Q522. Common emitter transistor configuration has:

(a) High current gain ✅

(b) Low current gain

(d) None

Explanation: Most widely used configuration for amplification.

Q523. Common collector transistor configuration has:

(a) High input resistance, low output resistance ✅

(b) Low input resistance, high output resistance

(d) None

Explanation: Used for impedance matching.

Q524. Logic gates are made using:

(a) Diodes and transistors ✅

(b) Resistors only

(d) None

Explanation: Basic building blocks of digital circuits.

Q525. Integrated circuits (ICs) are:

(a) Miniaturized circuits on semiconductor chip ✅

(b) Large circuits

(d) None

Explanation: Contain thousands of components on a single chip, used in modern electronics.

Q526. Logic gates are:

(a) Basic building blocks of digital circuits ✅

(b) Mechanical devices

(d) None

Explanation: Logic gates perform Boolean operations (AND, OR, NOT, etc.) on binary inputs.

Q527. Boolean algebra deals with:

(a) Binary variables (0 and 1) ✅

(b) Decimal variables

(d) None

Explanation: Boolean algebra simplifies logic circuits using binary values.

Q528. AND gate output is 1 when:

(a) Both inputs are 1 ✅

(b) Any input is 1

(d) None

Explanation: Logical multiplication. Output = A·B.

Q529. OR gate output is 1 when:

(a) Any input is 1 ✅

(b) Both inputs are 0

(d) None

Explanation: Logical addition. Output = A + B.

Q530. NOT gate output is:

(a) Complement of input ✅

(b) Same as input

(d) None

Explanation: Inverts input. Output = Ā.

Q531. NAND gate is:

(a) NOT of AND ✅

(b) NOT of OR

(d) None

Explanation: Output = ¯(A·B). Universal gate.

Q532. NOR gate is:

(a) NOT of OR ✅

(b) NOT of AND

(d) None

Explanation: Output = ¯(A + B). Universal gate.

Q533. XOR gate output is 1 when:

(a) Inputs are different ✅

(b) Inputs are same

(d) None

Explanation: Exclusive OR. Output = A⊕B.

Q534. XNOR gate output is 1 when:

(a) Inputs are same ✅

(b) Inputs are different

(d) None

Explanation: Exclusive NOR. Output = ¯(A⊕B).

Q535. Universal gates are:

(a) NAND and NOR ✅

(b) AND and OR

(d) None

Explanation: Any logic function can be implemented using NAND or NOR alone.

Q536. Truth table shows:

(a) All possible input-output combinations ✅

(b) Only one output

(d) None

Explanation: Used to design and analyze logic circuits.

Q537. Boolean expression for AND gate:

(a) Y = A·B ✅

(b) Y = A + B

(d) None

Explanation: Logical multiplication.

Q538. Boolean expression for OR gate:

(a) Y = A + B ✅

(b) Y = A·B

(d) None

Explanation: Logical addition.

Q539. Boolean expression for NOT gate:

(a) Y = Ā ✅

(b) Y = A

(d) None

Explanation: Logical inversion.

Q540. De Morgan’s first law:

(a) ¯(A·B) = Ā + B̄ ✅

(b) ¯(A + B) = Ā·B̄

(d) None

Explanation: Converts AND into OR with complements.

Q541. De Morgan’s second law:

(a) ¯(A + B) = Ā·B̄ ✅

(b) ¯(A·B) = Ā + B̄

(d) None

Explanation: Converts OR into AND with complements.

Q542. Simplification of Boolean expressions reduces:

(a) Number of gates ✅

(b) Number of inputs

(d) None

Explanation: Minimization saves cost and power in circuits.

Q543. Half adder adds:

(a) Two binary digits ✅

(b) Three digits

(d) None

Explanation: Outputs sum and carry using XOR and AND gates.

Q544. Full adder adds:

(a) Three binary digits ✅

(b) Two digits

(d) None

Explanation: Inputs A, B, and carry-in. Outputs sum and carry-out.

Q545. Flip-flop is:

(a) Basic memory element ✅

(b) Logic gate

(d) None

Explanation: Stores one bit of information. Types: SR, JK, D, T.

Q546. SR flip-flop stands for:

(a) Set-Reset ✅

(b) Shift-Register

(d) None

Explanation: Basic flip-flop with set and reset inputs.

Q547. JK flip-flop avoids:

(a) Invalid state of SR flip-flop ✅

(b) Random state

Explanation: Modified SR flip-flop with feedback to prevent invalid condition.

Q548. D flip-flop is:

(a) Data or Delay flip-flop ✅

(b) Random

Explanation: Transfers input to output on clock edge. Used in registers.

Q549. T flip-flop is:

(a) Toggle flip-flop ✅

(b) Transfer flip-flop

(d) None

Explanation: Changes state on each clock pulse. Used in counters.

Q550. Counters are used to:

(a) Count pulses ✅

(b) Store data

(d) None

Explanation: Sequential circuits that count clock pulses. Types: up, down, ripple, synchronous.

Q551. Communication system consists of:

(a) Transmitter, channel, receiver ✅

(b) Only transmitter

(d) None

Explanation: A complete system requires source to send, medium to carry, and destination to receive information.

Q552. Modulation is:

(a) Superimposing information signal on carrier wave ✅

(b) Removing carrier wave

(d) None

Explanation: Enables transmission of low-frequency signals over long distances.

Q553. Types of modulation include:

(a) AM, FM, PM ✅

(b) AC, DC

(d) None

Explanation: Amplitude, frequency, and phase modulation are common techniques.

Q554. Amplitude modulation (AM) varies:

(a) Amplitude of carrier wave ✅

(b) Frequency of carrier wave

(d) None

Explanation: Carrier amplitude changes according to signal.

Q555. Frequency modulation (FM) varies:

(a) Frequency of carrier wave ✅

(b) Amplitude of carrier wave

(d) None

Explanation: Carrier frequency changes according to signal.

Q556. Phase modulation (PM) varies:

(a) Phase of carrier wave ✅

(b) Amplitude of carrier wave

(d) None

Explanation: Carrier phase changes according to signal.

Q557. Demodulation is:

(a) Extracting information from carrier wave ✅

(b) Adding carrier wave

(d) None

Explanation: Receiver recovers original signal from modulated wave.

Q558. Antenna is used to:

(a) Transmit or receive electromagnetic waves ✅

(b) Store energy

(d) None

Explanation: Converts electrical signals into electromagnetic waves and vice versa.

Q559. Bandwidth of communication channel is:

(a) Range of frequencies transmitted ✅

(b) Voltage range

(d) None

Explanation: Determines data capacity of channel.

Q560. Satellite communication uses:

(a) Microwaves ✅

(b) Radio waves

(d) None

Explanation: Microwaves penetrate atmosphere and are used for satellite links.

Q561. Optical fiber communication uses:

(a) Light waves ✅

(b) Radio waves

(d) None

Explanation: Light signals travel through fiber with minimal loss, enabling high-speed data transfer.

Q562. Advantage of optical fiber:

(a) High bandwidth and low loss ✅

(b) High loss

(d) None

Explanation: Optical fibers provide fast, reliable communication.

Q563. Mobile communication uses:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Mobile phones transmit and receive signals using radio frequencies.

Q564. Television broadcasting uses:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Audio and video signals transmitted via radio waves.

Q565. Internet data transfer uses:

(a) Optical fiber and radio waves ✅

(b) Gamma rays

(d) None

Explanation: Combination of fiber optics and wireless signals enables global connectivity.

Q566. Radar works on:

(a) Reflection of microwaves ✅

(b) Reflection of radio waves

(d) None

Explanation: Radar detects objects by sending microwaves and analyzing reflected signals.

Q567. GPS stands for:

(a) Global Positioning System ✅

(b) General Power System

(d) None

Explanation: Satellite-based navigation system providing location and time information.

Q568. Bluetooth technology uses:

(a) Short-range radio waves ✅

(b) Infrared

(d) None

Explanation: Enables wireless communication between devices over short distances.

Q569. Wi-Fi technology uses:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Provides wireless internet connectivity using radio frequencies.

Q570. AM radio operates in:

(a) Medium frequency band ✅

(b) High frequency band

(d) None

Explanation: AM radio uses medium frequency range (MF band).

Q571. FM radio operates in:

(a) Very high frequency band ✅

(b) Medium frequency band

(d) None

Explanation: FM radio uses VHF band, providing better sound quality.

Q572. Television signals use:

(a) VHF and UHF bands ✅

(b) LF band

(d) None

Explanation: Video and audio transmitted using very high and ultra-high frequency bands.

Q573. Microwave communication is used for:

(a) Long-distance telephone and TV transmission ✅

(b) Cooking only

(d) None

Explanation: Microwaves carry signals over long distances via line-of-sight.

Q574. Infrared communication is used in:

(a) Remote controls ✅

(b) Satellite links

(d) None

Explanation: Infrared signals transmit data between remote and device.

Q575. Bandwidth requirement is higher for:

(a) Video signals ✅

(b) Audio signals

(d) None

Explanation: Video requires more data capacity than audio or text.

Q576. Amplifier is used to:

(a) Increase signal strength ✅

(b) Decrease signal strength

(d) None

Explanation: Amplifier boosts weak input signals without changing their shape.

Q577. Basic transistor amplifier configuration:

(a) Common emitter ✅

(b) Common base

(d) None

Explanation: Common emitter provides high current and voltage gain, widely used.

Q578. Voltage gain of amplifier is:

(a) Ratio of output voltage to input voltage ✅

(b) Ratio of input to output

(d) None

Explanation: Av = Vout/Vin. Indicates amplification factor.

Q579. Current gain of transistor is:

(a) β = Ic/Ib ✅

(b) β = Ib/Ic

(d) None

Explanation: Ratio of collector current to base current. Typically 20–200.

Q580. Power gain of amplifier is:

(a) Product of voltage and current gain ✅

(b) Ratio of input to output

(d) None

Explanation: Ap = Av × Ai. Indicates overall amplification.

Q581. Oscillator is:

(a) Circuit generating AC without input ✅

(b) Circuit amplifying signals

(d) None

Explanation: Produces continuous waveform using feedback.

Q582. Oscillator requires:

(a) Positive feedback ✅

(b) Negative feedback

(d) None

Explanation: Positive feedback sustains oscillations.

Q583. LC oscillator uses:

(a) Inductor and capacitor ✅

(b) Resistor and capacitor

(d) None

Explanation: Tank circuit of L and C determines frequency.

Q584. RC oscillator uses:

(a) Resistor and capacitor ✅

(b) Inductor and capacitor

(d) None

Explanation: RC network provides phase shift for oscillation.

Q585. Crystal oscillator uses:

(a) Piezoelectric crystal ✅

(b) Inductor

(d) None

Explanation: Quartz crystal provides stable frequency, used in watches and communication.

Q586. Feedback in amplifier is:

(a) Portion of output fed to input ✅

(b) Input fed to output

(d) None

Explanation: Feedback controls gain and stability.

Q587. Negative feedback in amplifier:

(a) Reduces gain but improves stability ✅

(b) Increases gain

(d) None

Explanation: Reduces distortion and increases bandwidth.

Q588. Positive feedback in amplifier:

(a) Increases gain, may cause oscillations ✅

(b) Reduces gain

(d) None

Explanation: Used in oscillators to sustain signals.

Q589. Operational amplifier (Op-amp) is:

(a) High-gain differential amplifier ✅

(b) Low-gain amplifier

(d) None

Explanation: Amplifies difference between two inputs. Used in analog circuits.

Q590. Ideal op-amp has:

(a) Infinite gain, infinite input resistance, zero output resistance ✅

(b) Finite gain

(d) None

Explanation: Ideal characteristics simplify analysis.

Q591. Inverting amplifier output is:

(a) 180° out of phase with input ✅

(b) In phase

(d) None

Explanation: Negative input terminal used, output inverted.

Q592. Non-inverting amplifier output is:

(a) In phase with input ✅

(b) Out of phase

(d) None

Explanation: Positive input terminal used, output same phase.

Q593. Voltage follower has:

(a) Unity gain ✅

(b) Infinite gain

(d) None

Explanation: Output follows input. Used for buffering.

Q594. Summing amplifier adds:

(a) Multiple input voltages ✅

(b) Multiplies inputs

(d) None

Explanation: Op-amp configuration that sums signals.

Q595. Differential amplifier amplifies:

(a) Difference between two inputs ✅

(b) Sum of inputs

(d) None

Explanation: Rejects common signals, amplifies difference.

Q596. Instrumentation amplifier is:

(a) High precision differential amplifier ✅

(b) Low precision amplifier

(d) None

Explanation: Used in medical and scientific instruments for accurate measurements.

Q597. Oscillator frequency depends on:

(a) Circuit components (L, C, R, crystal) ✅

(b) Voltage only

(d) None

Explanation: Frequency determined by reactive components.

Q598. Wien bridge oscillator uses:

(a) RC network ✅

(b) LC network

(d) None

Explanation: Produces sine waves with good stability.

Q599. Colpitts oscillator uses:

(a) Capacitive divider with inductor ✅

(b) Resistive divider

(d) None

Explanation: LC circuit with capacitive feedback determines frequency.

Q600. Hartley oscillator uses:

(a) Inductive divider with capacitor ✅

(b) Capacitive divider

(d) None

Explanation: LC circuit with inductive feedback determines frequency.

Q601. Radio waves are used in:

(a) Broadcasting and communication ✅

(b) Cooking

(d) None

Explanation: Long wavelength, low frequency waves ideal for radio, TV, and mobile communication.

Q602. Microwaves are used in:

(a) Radar and cooking ✅

(b) X-ray imaging

(d) None

Explanation: Microwaves heat food and are used in radar systems and satellite communication.

Q603. Infrared waves are used in:

(a) Remote controls and thermal imaging ✅

(b) X-rays

(d) None

Explanation: Infrared radiation is emitted by hot bodies, used in sensors and remotes.

Q604. Visible light is used in:

(a) Human vision ✅

(b) Cooking

(d) None

Explanation: Range 400–700 nm is detectable by human eyes.

Q605. Ultraviolet rays are used in:

(a) Sterilization ✅

(b) Cooking

(d) None

Explanation: UV kills bacteria, used in medical sterilization and water purification.

Q606. X-rays are used in:

(a) Medical imaging ✅

(b) Cooking

(d) None

Explanation: High energy rays penetrate tissues, used in radiography.

Q607. Gamma rays are used in:

(a) Cancer treatment ✅

(b) Cooking

(d) None

Explanation: Very high energy rays destroy cancer cells and sterilize equipment.

Q608. Electromagnetic waves are produced by:

(a) Accelerated charges ✅

(b) Stationary charges

(d) None

Explanation: Changing electric field produces magnetic field and vice versa, propagating as waves.

Q609. Mobile phones use:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Mobile communication relies on radio frequency signals.

Q610. Television broadcasting uses:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Audio and video signals transmitted via radio waves.

Q611. Internet data transfer uses:

(a) Optical fiber and radio waves ✅

(b) Gamma rays

(d) None

Explanation: Combination of fiber optics and wireless signals enables global connectivity.

Q612. Radar works on:

(a) Reflection of microwaves ✅

(b) Reflection of radio waves

(d) None

Explanation: Radar detects objects by sending microwaves and analyzing reflected signals.

Q613. GPS stands for:

(a) Global Positioning System ✅

(b) General Power System

(d) None

Explanation: Satellite-based navigation system providing location and time information.

Q614. Bluetooth technology uses:

(a) Short-range radio waves ✅

(b) Infrared

(d) None

Explanation: Enables wireless communication between devices over short distances.

Q615. Wi-Fi technology uses:

(a) Radio waves ✅

(b) Infrared

(d) None

Explanation: Provides wireless internet connectivity using radio frequencies.

Q616. AM radio operates in:

(a) Medium frequency band ✅

(b) High frequency band

(d) None

Explanation: AM radio uses medium frequency range (MF band).

Q617. FM radio operates in:

(a) Very high frequency band ✅

(b) Medium frequency band

(d) None

Explanation: FM radio uses VHF band, providing better sound quality.

Q618. Television signals use:

(a) VHF and UHF bands ✅

(b) LF band

(d) None

Explanation: Video and audio transmitted using very high and ultra-high frequency bands.

Q619. Microwave communication is used for:

(a) Long-distance telephone and TV transmission ✅

(b) Cooking only

(d) None

Explanation: Microwaves carry signals over long distances via line-of-sight.

Q620. Infrared communication is used in:

(a) Remote controls ✅

(b) Satellite links

(d) None

Explanation: Infrared signals transmit data between remote and device.

Q621. Bandwidth requirement is higher for:

(a) Video signals ✅

(b) Audio signals

(d) None

Explanation: Video requires more data capacity than audio or text.

Q622. Optical fiber communication advantage:

(a) High bandwidth and low loss ✅

(b) High loss

(d) None

Explanation: Optical fibers provide fast, reliable communication.

Q623. Satellite communication uses:

(a) Microwaves ✅

(b) Infrared

(d) None

Explanation: Microwaves penetrate atmosphere and are used for satellite links.

Q624. Electromagnetic waves travel fastest in:

(a) Vacuum ✅

(b) Air

(d) None

Explanation: Speed in vacuum is c = 3 × 10⁸ m/s. Slower in other media.

Q625. Electromagnetic waves are:

(a) Transverse ✅

(b) Longitudinal

(d) None

Explanation: Electric and magnetic fields oscillate perpendicular to each other and to direction of propagation.

Q626. Dual nature of light means:

(a) Light shows both wave and particle nature ✅

(b) Only wave nature

(d) None

Explanation: Light exhibits interference and diffraction (wave) as well as photoelectric effect (particle).

Q627. Wave nature of electrons was proposed by:

(a) de Broglie ✅

(b) Einstein

(d) None

Explanation: de Broglie suggested matter waves with wavelength λ = h/p.

Q628. de Broglie wavelength formula:

(a) λ = h/p ✅

(b) λ = p/h

(d) None

Explanation: Wavelength inversely proportional to momentum.

Q629. Electron microscope works on:

(a) Wave nature of electrons ✅

(b) Particle nature of electrons

(d) None

Explanation: Short de Broglie wavelength of electrons gives high resolution.

Q630. Davisson-Germer experiment proved:

(a) Wave nature of electrons ✅

(b) Particle nature of electrons

(d) None

Explanation: Electron diffraction confirmed de Broglie hypothesis.

Q631. Heisenberg uncertainty principle states:

(a) Δx·Δp ≥ h/4π ✅

(b) Δx·Δp = 0

(d) None

Explanation: Position and momentum cannot be measured simultaneously with precision.

Q632. Uncertainty principle applies to:

(a) Microscopic particles ✅

(b) Macroscopic bodies

(d) None

Explanation: Significant only for small particles like electrons.

Q633. Planck’s quantum theory states:

(a) Energy is quantized ✅

(b) Energy is continuous

(d) None

Explanation: Energy emitted/absorbed in discrete packets called quanta.

Q634. Quantum of light is:

(a) Photon ✅

(b) Electron

(d) None

Explanation: Photon carries energy E = hf.

Q635. Energy of photon depends on:

(a) Frequency ✅

(b) Intensity

(d) None

Explanation: Higher frequency → higher photon energy.

Q636. Intensity of light depends on:

(a) Number of photons ✅

(b) Energy of photons

(d) None

Explanation: More photons per unit time → higher intensity.

Q637. Compton effect proves:

(a) Particle nature of light ✅

(b) Wave nature of light

(d) None

Explanation: Photon collides with electron, showing momentum transfer.

Q638. Pair production is:

(a) Photon converts into electron-positron pair ✅

(b) Electron converts into photon

(d) None

Explanation: Requires photon energy ≥ 1.02 MeV.

Q639. Pair annihilation is:

(a) Electron and positron annihilate to produce photons ✅

(b) Photon annihilates into electron

(d) None

Explanation: Produces two gamma photons.

Q640. Quantum mechanics is based on:

(a) Schrödinger wave equation ✅

(b) Newton’s laws

(d) None

Explanation: Describes behavior of microscopic particles.

Q641. Schrödinger equation gives:

(a) Probability distribution of particles ✅

(b) Exact path of particles

(d) None

Explanation: Predicts likelihood of finding particle at position.

Q642. Probability interpretation of wave function was given by:

(a) Born ✅

(b) Schrödinger

(d) None

Explanation: |ψ|² gives probability density.

Q643. Atomic spectra are explained by:

(a) Quantum theory ✅

(b) Classical theory

(d) None

Explanation: Discrete energy levels cause line spectra.

Q644. Hydrogen atom spectrum lines are:

(a) Lyman, Balmer, Paschen series ✅

(b) Random series

Explanation: Each series corresponds to transitions ending at specific energy levels.

Q645. Lyman series lies in:

(a) Ultraviolet region ✅

(b) Visible region

(d) None

Explanation: Transitions ending at n=1 produce UV lines.

Q646. Balmer series lies in:

(a) Visible region ✅

(b) Ultraviolet region

(d) None

Explanation: Transitions ending at n=2 produce visible lines.

Q647. Paschen series lies in:

(a) Infrared region ✅

(b) Visible region

(d) None

Explanation: Transitions ending at n=3 produce infrared lines.

Q648. Raman effect was discovered by:

(a) C.V. Raman ✅

(b) Einstein

(d) None

Explanation: Scattering of light with change in wavelength due to molecular vibrations.

Q649. Raman effect proves:

(a) Quantum nature of light-matter interaction ✅

(b) Classical scattering

(d) None

Explanation: Energy exchange between photons and molecules.

Q650. Raman effect is used in:

(a) Spectroscopy and chemical analysis ✅

(b) Cooking

(d) None

Explanation: Identifies molecular structure and composition.

Q651. Atomic spectra arise due to:

(a) Electronic transitions between energy levels ✅

(b) Nuclear transitions

(d) None

Explanation: Electrons jump between quantized orbits, emitting/absorbing photons of specific energies.

Q652. Emission spectrum is produced when:

(a) Electron falls to lower energy level ✅

(b) Electron jumps to higher level

(d) None

Explanation: Energy difference released as photon, giving bright lines on dark background.

Q653. Absorption spectrum is produced when:

(a) Electron jumps to higher energy level ✅

(b) Electron falls to lower level

(d) None

Explanation: Photon absorbed, leaving dark lines on bright background.

Q654. Hydrogen atom spectrum lines are grouped into:

(a) Lyman, Balmer, Paschen series ✅

(b) Random series

Explanation: Each series corresponds to transitions ending at specific energy levels.

Q655. Lyman series lies in:

(a) Ultraviolet region ✅

(b) Visible region

(d) None

Explanation: Transitions ending at n=1 produce UV lines.

Q656. Balmer series lies in:

(a) Visible region ✅

(b) Ultraviolet region

(d) None

Explanation: Transitions ending at n=2 produce visible lines.

Q657. Paschen series lies in:

(a) Infrared region ✅

(b) Visible region

(d) None

Explanation: Transitions ending at n=3 produce infrared lines.

Q658. Spectral lines prove:

(a) Quantized energy levels ✅

(b) Continuous energy levels

(d) None

Explanation: Discrete lines show electrons occupy fixed energy states.

Q659. Molecular spectra arise due to:

(a) Vibrational and rotational transitions ✅

(b) Nuclear transitions

(d) None

Explanation: Molecules have vibrational and rotational energy levels in addition to electronic.

Q660. Vibrational spectra lie in:

(a) Infrared region ✅

(b) Visible region

(d) None

Explanation: Vibrational transitions correspond to IR frequencies.

Q661. Rotational spectra lie in:

(a) Microwave region ✅

(b) Visible region

(d) None

Explanation: Rotational transitions correspond to microwave frequencies.

Q662. Raman effect involves:

(a) Scattering of light with change in wavelength ✅

(b) Absorption of light

(d) None

Explanation: Incident photon interacts with molecule, energy exchanged.

Q663. Stokes lines in Raman spectrum are:

(a) Shifted to longer wavelength ✅

(b) Shifted to shorter wavelength

(d) None

Explanation: Photon loses energy to molecule, wavelength increases.

Q664. Anti-Stokes lines in Raman spectrum are:

(a) Shifted to shorter wavelength ✅

(b) Shifted to longer wavelength

(d) None

Explanation: Photon gains energy from molecule, wavelength decreases.

Q665. Raman effect proves:

(a) Quantum nature of light-matter interaction ✅

(b) Classical scattering

(d) None

Explanation: Energy exchange between photons and molecules is quantized.

Q666. Raman effect discovered by:

(a) C.V. Raman ✅

(b) Einstein

(d) None

Explanation: Nobel Prize awarded in 1930 for discovery.

Q667. Raman spectroscopy is used in:

(a) Chemical analysis ✅

(b) Cooking

(d) None

Explanation: Identifies molecular structure and composition.

Q668. Infrared spectroscopy is used to study:

(a) Vibrational transitions ✅

(b) Rotational transitions

(d) None

Explanation: IR absorption reveals molecular vibrations.

Q669. Microwave spectroscopy is used to study:

(a) Rotational transitions ✅

(b) Vibrational transitions

(d) None

Explanation: Microwave absorption reveals rotational energy levels.

Q670. Ultraviolet spectroscopy is used to study:

(a) Electronic transitions ✅

(b) Vibrational transitions

(d) None

Explanation: UV absorption excites electrons to higher energy states.

Q671. Visible spectroscopy is used to study:

(a) Electronic transitions in visible range ✅

(b) Vibrational transitions

(d) None

Explanation: Explains color of compounds and solutions.

Q672. Nuclear Magnetic Resonance (NMR) spectroscopy studies:

(a) Magnetic properties of nuclei ✅

(b) Vibrational transitions

(d) None

Explanation: NMR reveals chemical environment of nuclei, used in chemistry and medicine.

Q673. Mass spectrometry is used to determine:

(a) Molecular mass and structure ✅

(b) Vibrational transitions

(d) None

Explanation: Ionized molecules separated by mass-to-charge ratio.

Q674. X-ray spectroscopy is used to study:

(a) Inner electronic transitions ✅

(b) Vibrational transitions

(d) None

Explanation: X-rays excite core electrons, revealing atomic structure.

Q675. Spectroscopy overall is used for:

(a) Identifying structure and composition of matter ✅

(b) Cooking

(d) None

Explanation: Provides detailed information about atoms and molecules.

Q676. Solid state physics deals with:

(a) Properties of solids ✅

(b) Properties of liquids

(d) None

Explanation: Studies structure, electrical, magnetic, and thermal properties of solids.

Q677. Crystalline solids have:

(a) Regular arrangement of atoms ✅

(b) Random arrangement

(d) None

Explanation: Atoms arranged in repeating pattern, giving definite shape.

Q678. Amorphous solids have:

(a) Irregular arrangement of atoms ✅

(b) Regular arrangement

(d) None

Explanation: No long-range order. Examples: glass, plastics.

Q679. Unit cell is:

(a) Smallest repeating unit of crystal ✅

(b) Largest unit

(d) None

Explanation: Defines crystal structure by repeating in space.

Q680. Types of cubic unit cells:

(a) Simple, body-centered, face-centered ✅

(b) Hexagonal only

(d) None

Explanation: Three main cubic structures in crystals.

Q681. Coordination number is:

(a) Number of nearest neighbors ✅

(b) Number of atoms in unit cell

(d) None

Explanation: Indicates how many atoms surround a given atom.

Q682. Electrical conductivity is highest in:

(a) Metals ✅

(b) Semiconductors

(d) None

Explanation: Metals have free electrons for conduction.

Q683. Electrical conductivity is lowest in:

(a) Insulators ✅

(b) Metals

(d) None

Explanation: No free electrons. Examples: rubber, glass.

Q684. Semiconductors have conductivity:

(a) Between metals and insulators ✅

(b) Higher than metals

(d) None

Explanation: Conductivity depends on temperature and doping.

Q685. Band theory explains:

(a) Electrical properties of solids ✅

(b) Thermal properties only

(d) None

Explanation: Energy bands determine whether material is conductor, semiconductor, or insulator.

Q686. In conductors:

(a) Valence band overlaps conduction band ✅

(b) Large band gap

(d) None

Explanation: Free electrons move easily, allowing conduction.

Q687. In insulators:

(a) Large band gap (> 3 eV) ✅

(b) Small band gap

(d) None

Explanation: Electrons cannot jump to conduction band easily.

Q688. In semiconductors:

(a) Small band gap (~1 eV) ✅

(b) Large band gap

(d) None

Explanation: Electrons can jump with small energy input.

Q689. Intrinsic semiconductor conductivity increases with:

(a) Temperature ✅

(b) Pressure

(d) None

Explanation: Higher temperature excites more electrons to conduction band.

Q690. Extrinsic semiconductor conductivity depends on:

(a) Doping ✅

(b) Pressure

(d) None

Explanation: Impurities add carriers, increasing conductivity.

Q691. Superconductors have:

(a) Zero resistance below critical temperature ✅

(b) Infinite resistance

(d) None

Explanation: Exhibit perfect conductivity and expel magnetic fields.

Q692. Critical temperature is:

(a) Temperature below which material becomes superconducting ✅

(b) Temperature above which material melts

(d) None

Explanation: Each superconductor has specific Tc.

Q693. Meissner effect is:

(a) Expulsion of magnetic field from superconductor ✅

(b) Attraction of magnetic field

(d) None

Explanation: Defines true superconductivity.

Q694. Superconductors are used in:

(a) MRI machines, maglev trains ✅

(b) Cooking

(d) None

Explanation: Zero resistance and strong magnetic fields enable advanced applications.

Q695. High-temperature superconductors have Tc:

(a) Above liquid nitrogen temperature (77 K) ✅

(b) Below 10 K

(d) None

Explanation: Easier to use practically than low-Tc superconductors.

Q696. Example of high-Tc superconductor:

(a) Yttrium barium copper oxide (YBCO) ✅

(b) Silicon

(d) None

Explanation: Ceramic material with Tc ~ 92 K.

Q697. Crystal defects are:

(a) Irregularities in lattice ✅

(b) Perfect arrangement

(d) None

Explanation: Vacancies, interstitials, dislocations affect properties.

Q698. Point defects include:

(a) Vacancy, interstitial, substitutional ✅

(b) Dislocation

(d) None

Explanation: Localized irregularities at atomic scale.

Q699. Line defects include:

(a) Dislocations ✅

(b) Vacancies

(d) None

Explanation: Irregularities along a line in crystal lattice.

Q700. Applications of solid state physics include:

(a) Electronics, superconductors, materials science ✅

(b) Cooking

(d) None

Explanation: Basis for modern technology like semiconductors, ICs, and superconducting devices.

Q701. Reflection of light follows:

(a) Laws of reflection ✅

(b) Laws of refraction

(d) None

Explanation: Angle of incidence = angle of reflection, and incident ray, reflected ray, and normal lie in same plane.

Q702. Refraction of light occurs due to:

(a) Change in speed of light ✅

(b) Change in frequency

(d) None

Explanation: Light bends when passing between media of different refractive indices.

Q703. Refractive index is:

(a) Ratio of speed of light in vacuum to speed in medium ✅

(b) Ratio of frequency

(d) None

Explanation: n = c/v. Determines bending of light.

Q704. Snell’s law states:

(a) n₁ sin i = n₂ sin r ✅

(b) i = r

(d) None

Explanation: Governs refraction between two media.

Q705. Total internal reflection occurs when:

(a) Angle of incidence > critical angle ✅

(b) Angle of incidence < critical angle

(d) None

Explanation: Light reflects completely inside denser medium.

Q706. Critical angle is:

(a) Angle of incidence for 90° refraction ✅

(b) Angle of reflection

(d) None

Explanation: Beyond this angle, total internal reflection occurs.

Q707. Optical fiber works on:

(a) Total internal reflection ✅

(b) Diffraction

(d) None

Explanation: Light signals guided through fiber by repeated internal reflection.

Q708. Convex lens is:

(a) Converging lens ✅

(b) Diverging lens

(d) None

Explanation: Focuses parallel rays to a point.

Q709. Concave lens is:

(a) Diverging lens ✅

(b) Converging lens

(d) None

Explanation: Spreads parallel rays outward.

Q710. Focal length of lens depends on:

(a) Curvature and refractive index ✅

(b) Thickness only

(d) None

Explanation: Lens maker’s formula relates focal length to curvature and refractive index.

Q711. Power of lens is:

(a) Reciprocal of focal length in meters ✅

(b) Focal length itself

(d) None

Explanation: P = 100/f(cm). Measured in diopters.

Q712. Magnification of lens is:

(a) Ratio of image height to object height ✅

(b) Ratio of object to image

(d) None

Explanation: Determines size of image relative to object.

Q713. Real image is:

(a) Formed by actual intersection of rays ✅

(b) Formed by apparent intersection

(d) None

Explanation: Can be projected on screen.

Q714. Virtual image is:

(a) Formed by apparent intersection of rays ✅

(b) Formed by actual intersection

(d) None

Explanation: Cannot be projected on screen.

Q715. Convex mirror always forms:

(a) Virtual, diminished image ✅

(b) Real, enlarged image

(d) None

Explanation: Used in vehicles for wide field of view.

Q716. Concave mirror can form:

(a) Real or virtual images depending on object position ✅

(b) Only virtual images

(d) None

Explanation: Versatile mirror used in telescopes and headlights.

Q717. Plane mirror forms:

(a) Virtual, same size image ✅

(b) Real image

(d) None

Explanation: Image upright and laterally inverted.

Q718. Simple microscope uses:

(a) Convex lens ✅

(b) Concave lens

(d) None

Explanation: Magnifies small objects using converging lens.

Q719. Compound microscope uses:

(a) Two convex lenses ✅

(b) Two concave lenses

(d) None

Explanation: Objective lens forms real image, eyepiece magnifies it.

Q720. Telescope is used to:

(a) View distant objects ✅

(b) View nearby objects

(d) None

Explanation: Combines objective and eyepiece lenses.

Q721. Astronomical telescope uses:

(a) Convex objective and convex eyepiece ✅

(b) Concave lenses

(d) None

Explanation: Produces magnified inverted image of distant objects.

Q722. Terrestrial telescope uses:

(a) Convex objective, convex eyepiece, erecting lens ✅

(b) Concave lenses

(d) None

Explanation: Produces magnified upright image for terrestrial viewing.

Q723. Magnifying power of telescope depends on:

(a) Ratio of focal lengths of objective and eyepiece ✅

(b) Ratio of diameters

(d) None

Explanation: M = fo/fe. Larger objective focal length increases magnification.

Q724. Prism works on:

(a) Refraction and dispersion ✅

(b) Reflection only

(d) None

Explanation: Splits white light into spectrum due to wavelength dependence of refractive index.

Q725. Spectrometer is used to:

(a) Measure angles of prism and refractive index ✅

(b) Measure current

(d) None

Explanation: Optical instrument for precise angular measurements in experiments.

Q726. Wave optics deals with:

(a) Phenomena like interference, diffraction, polarization ✅

(b) Reflection only

(d) None

Explanation: Explains light behavior when wave nature is considered.

Q727. Young’s double-slit experiment proves:

(a) Wave nature of light ✅

(b) Particle nature of light

(d) None

Explanation: Interference fringes show superposition of waves.

Q728. Condition for constructive interference:

(a) Path difference = nλ ✅

(b) Path difference = (2n+1)λ/2

(d) None

Explanation: Waves reinforce each other when path difference is integral multiple of wavelength.

Q729. Condition for destructive interference:

(a) Path difference = (2n+1)λ/2 ✅

(b) Path difference = nλ

(d) None

Explanation: Waves cancel each other when path difference is odd multiple of half wavelength.

Q730. Fringe width in Young’s experiment:

(a) β = λD/d ✅

(b) β = d/λD

(d) None

Explanation: Depends on wavelength, distance to screen, and slit separation.

Q731. Diffraction is:

(a) Bending of light around obstacles ✅

(b) Reflection

(d) None

Explanation: Wave spreads into geometrical shadow region.

Q732. Diffraction is more pronounced for:

(a) Larger wavelength ✅

(b) Smaller wavelength

(d) None

Explanation: Longer wavelengths bend more around obstacles.

Q733. Single-slit diffraction central maximum is:

(a) Twice width of other maxima ✅

(b) Same width

(d) None

Explanation: Central bright fringe is wider than side fringes.

Q734. Condition for minima in single-slit diffraction:

(a) a sin θ = nλ ✅

(b) a cos θ = nλ

(d) None

Explanation: Destructive interference occurs at these angles.

Q735. Resolving power of optical instrument depends on:

(a) Wavelength and aperture ✅

(b) Voltage

(d) None

Explanation: Smaller wavelength and larger aperture improve resolution.

Q736. Polarization is:

(a) Restricting vibrations of light to one plane ✅

(b) Random vibrations

(d) None

Explanation: Light waves normally vibrate in all directions perpendicular to propagation.

Q737. Polarization proves:

(a) Transverse nature of light ✅

(b) Longitudinal nature

(d) None

Explanation: Only transverse waves can be polarized.

Q738. Plane-polarized light is:

(a) Vibrations confined to one plane ✅

(b) Vibrations in all planes

(d) None

Explanation: Produced by polarizers like polaroid sheets.

Q739. Unpolarized light is:

(a) Vibrations in all directions perpendicular to propagation ✅

(b) Vibrations in one plane

(d) None

Explanation: Natural light is unpolarized.

Q740. Polarizers are used to:

(a) Produce polarized light ✅

(b) Produce unpolarized light

(d) None

Explanation: Polaroid sheets filter vibrations to one plane.

Q741. Brewster’s law states:

(a) tan iB = n ✅

(b) sin iB = n

(d) None

Explanation: At Brewster angle, reflected light is completely polarized.

Q742. Polarization by reflection occurs at:

(a) Brewster angle ✅

(b) Critical angle

(d) None

Explanation: Reflected light becomes plane-polarized.

Q743. Polarization by scattering explains:

(a) Blue color of sky ✅

(b) Red color of sunset

(d) None

Explanation: Shorter wavelengths scatter more, making sky appear blue.

Q744. Polaroid sunglasses work by:

(a) Reducing glare using polarization ✅

(b) Increasing brightness

(d) None

Explanation: Block horizontally polarized reflected light.

Q745. Optical activity is:

(a) Rotation of plane of polarized light ✅

(b) Reflection of light

(d) None

Explanation: Certain substances rotate polarization plane.

Q746. Nicol prism is used to:

(a) Produce polarized light ✅

(b) Produce unpolarized light

(d) None

Explanation: Splits ordinary and extraordinary rays, transmitting polarized light.

Q747. Double refraction occurs in:

(a) Birefringent crystals ✅

(b) Metals

(d) None

Explanation: Crystals like calcite split light into ordinary and extraordinary rays.

Q748. Malus’ law states:

(a) I = I₀ cos²θ ✅

(b) I = I₀ sin²θ

(d) None

Explanation: Intensity of polarized light depends on angle between transmission axis and polarization direction.

Q749. Polarization is used in:

(a) Sunglasses, photography, stress analysis ✅

(b) Cooking

(d) None

Explanation: Practical applications exploit control of light vibrations.

Q750. Interference and diffraction together prove:

(a) Wave nature of light ✅

(b) Particle nature

(d) None

Explanation: Both phenomena arise from superposition and bending of waves.

Q751. Human eye works like:

(a) Camera with lens system ✅

(b) Microscope

(d) None

Explanation: Eye lens focuses light on retina, similar to camera lens focusing on film.

Q752. Retina of eye acts as:

(a) Screen ✅

(b) Lens

(d) None

Explanation: Image formed on retina is real and inverted, processed by brain.

Q753. Defect of eye where distant objects not seen clearly:

(a) Myopia (short-sightedness) ✅

(b) Hypermetropia

(d) None

Explanation: Image forms before retina. Corrected by concave lens.

Q754. Defect of eye where near objects not seen clearly:

(a) Hypermetropia (long-sightedness) ✅

(b) Myopia

(d) None

Explanation: Image forms behind retina. Corrected by convex lens.

Q755. Presbyopia occurs due to:

(a) Loss of elasticity of eye lens ✅

(b) Increase in elasticity

(d) None

Explanation: Common in old age, corrected by bifocal lenses.

Q756. Astigmatism is:

(a) Unequal curvature of cornea/lens ✅

(b) Equal curvature

(d) None

Explanation: Causes blurred vision. Corrected by cylindrical lenses.

Q757. Simple microscope uses:

(a) Convex lens ✅

(b) Concave lens

(d) None

Explanation: Magnifies small objects using converging lens.

Q758. Magnifying power of simple microscope:

(a) M = 1 + D/f ✅

(b) M = D/f

(d) None

Explanation: D = least distance of distinct vision (~25 cm).

Q759. Compound microscope uses:

(a) Two convex lenses ✅

(b) Two concave lenses

(d) None

Explanation: Objective lens forms real image, eyepiece magnifies it.

Q760. Magnifying power of compound microscope:

(a) M = (L/fo) × (D/fe) ✅

(b) M = fo/fe

(d) None

Explanation: Depends on focal lengths of objective and eyepiece.

Q761. Telescope is used to:

(a) View distant objects ✅

(b) View nearby objects

(d) None

Explanation: Combines objective and eyepiece lenses.

Q762. Astronomical telescope uses:

(a) Convex objective and convex eyepiece ✅

(b) Concave lenses

(d) None

Explanation: Produces magnified inverted image of distant objects.

Q763. Magnifying power of telescope:

(a) M = fo/fe ✅

(b) M = fe/fo

(d) None

Explanation: Ratio of focal lengths of objective and eyepiece.

Q764. Terrestrial telescope uses:

(a) Convex objective, convex eyepiece, erecting lens ✅

(b) Concave lenses

(d) None

Explanation: Produces magnified upright image for terrestrial viewing.

Q765. Reflecting telescope uses:

(a) Concave mirror as objective ✅

(b) Convex lens as objective

(d) None

Explanation: Mirror collects light, reducing chromatic aberration.

Q766. Refracting telescope uses:

(a) Convex lens as objective ✅

(b) Concave mirror

(d) None

Explanation: Lens collects and focuses light.

Q767. Binoculars are:

(a) Pair of telescopes for both eyes ✅

(b) Pair of microscopes

(d) None

Explanation: Provide magnified stereoscopic view of distant objects.

Q768. Camera works on principle of:

(a) Refraction through convex lens ✅

(b) Reflection

(d) None

Explanation: Lens focuses image on film or sensor.

Q769. Projector works on principle of:

(a) Refraction and magnification ✅

(b) Reflection only

(d) None

Explanation: Projects magnified image on screen using lenses.

Q770. Periscope works on principle of:

(a) Reflection by plane mirrors ✅

(b) Refraction

(d) None

Explanation: Used in submarines to see above water.

Q771. Spectacles correct:

(a) Eye defects ✅

(b) Hearing defects

(d) None

Explanation: Lenses compensate for myopia, hypermetropia, presbyopia, astigmatism.

Q772. Contact lenses are:

(a) Thin lenses placed on cornea ✅

(b) Thick lenses

(d) None

Explanation: Correct vision defects without spectacles.

Q773. Ophthalmoscope is used to:

(a) Examine interior of eye ✅

(b) Examine ear

(d) None

Explanation: Medical instrument for eye diagnosis.

Q774. Photometer is used to:

(a) Compare luminous intensities ✅

(b) Measure current

(d) None

Explanation: Measures brightness of light sources.

Q775. Optical instruments overall are used for:

(a) Vision correction, magnification, observation ✅

(b) Cooking

(d) None

Explanation: Applications range from spectacles to telescopes and microscopes.

Q776. Zeroth law of thermodynamics states:

(a) If two systems are in thermal equilibrium with a third, they are in equilibrium with each other ✅

(b) Energy cannot be created

(d) None

Explanation: Defines concept of temperature and thermal equilibrium.

Q777. First law of thermodynamics is:

(a) Energy conservation ✅

(b) Entropy increase

(d) None

Explanation: ΔU = Q – W. Internal energy change equals heat supplied minus work done.

Q778. Second law of thermodynamics states:

(a) Heat cannot spontaneously flow from cold to hot ✅

(b) Energy is conserved

(d) None

Explanation: Defines direction of natural processes and entropy increase.

Q779. Third law of thermodynamics states:

(a) Entropy of perfect crystal at 0 K is zero ✅

(b) Energy is conserved

(d) None

Explanation: Provides absolute reference for entropy.

Q780. Heat engine converts:

(a) Heat energy into mechanical work ✅

(b) Mechanical work into heat

(d) None

Explanation: Operates between hot and cold reservoirs.

Q781. Efficiency of heat engine is:

(a) η = W/Qh ✅

(b) η = Qh/W

(d) None

Explanation: Ratio of work output to heat input.

Q782. Carnot engine efficiency depends on:

(a) Temperatures of reservoirs ✅

(b) Pressure

(d) None

Explanation: η = 1 – Tc/Th. Maximum possible efficiency.

Q783. Refrigerator works on:

(a) Reverse heat engine cycle ✅

(b) Carnot engine

(d) None

Explanation: Transfers heat from cold body to hot body using work.

Q784. Coefficient of performance (COP) of refrigerator:

(a) COP = Qc/W ✅

(b) COP = W/Qc

(d) None

Explanation: Ratio of heat removed from cold body to work input.

Q785. Entropy is:

(a) Measure of disorder ✅

(b) Measure of energy

(d) None

Explanation: Increases in irreversible processes, constant in reversible.

Q786. In reversible process:

(a) Entropy remains constant ✅

(b) Entropy increases

(d) None

Explanation: Idealized process with no entropy change.

Q787. In irreversible process:

(a) Entropy increases ✅

(b) Entropy decreases

(d) None

Explanation: Natural processes always increase entropy.

Q788. Isothermal process occurs at:

(a) Constant temperature ✅

(b) Constant pressure

(d) None

Explanation: ΔU = 0, so Q = W.

Q789. Adiabatic process occurs at:

(a) No heat exchange ✅

(b) Constant temperature

(d) None

Explanation: Q = 0, so ΔU = –W.

Q790. Work done in isothermal expansion:

(a) W = nRT ln(Vf/Vi) ✅

(b) W = pΔV

(d) None

Explanation: Derived from ideal gas law at constant temperature.

Q791. Work done in adiabatic process:

(a) W = (pV – p’V’)/(γ – 1) ✅

(b) W = nRT ln(Vf/Vi)

(d) None

Explanation: Depends on initial and final states and γ (Cp/Cv).

Q792. Specific heat at constant pressure (Cp) is:

(a) Heat required to raise temperature at constant pressure ✅

(b) Heat at constant volume

(d) None

Explanation: Cp > Cv for gases.

Q793. Specific heat at constant volume (Cv) is:

(a) Heat required to raise temperature at constant volume ✅

(b) Heat at constant pressure

(d) None

Explanation: No work done, all heat increases internal energy.

Q794. Relation between Cp and Cv:

(a) Cp – Cv = R ✅

(b) Cp + Cv = R

(d) None

Explanation: Mayer’s relation for ideal gases.

Q795. Heat capacity is:

(a) Heat required to raise temperature of body by 1 K ✅

(b) Heat per unit mass

(d) None

Explanation: Extensive property depending on mass.

Q796. Specific heat is:

(a) Heat required to raise unit mass by 1 K ✅

(b) Heat for whole body

(d) None

Explanation: Intensive property independent of mass.

Q797. Latent heat is:

(a) Heat required for phase change without temperature change ✅

(b) Heat for temperature rise

(d) None

Explanation: Example: melting, boiling.

Q798. Heat engine efficiency is always:

(a) Less than Carnot efficiency ✅

(b) Equal to Carnot efficiency

(d) None

Explanation: Real engines have losses, so efficiency < ideal Carnot.

Q799. Practical applications of thermodynamics include:

(a) Engines, refrigerators, power plants ✅

(b) Cooking only

(d) None

Explanation: Governs energy conversion systems.

Q800. Thermodynamics overall studies:

(a) Heat, work, energy transformations ✅

(b) Only heat

(d) None

Explanation: Fundamental branch of physics for energy systems.

Q801. Heat transfer occurs by:

(a) Conduction, convection, radiation ✅

(b) Only conduction

(d) None

Explanation: Three fundamental modes of heat transfer in physics.

Q802. Conduction is:

(a) Heat transfer through solids without movement of particles ✅

(b) Heat transfer through fluids

(d) None

Explanation: Energy transferred by molecular vibrations and free electrons.

Q803. Good conductors of heat are:

(a) Metals ✅

(b) Wood

(d) None

Explanation: Free electrons in metals carry heat efficiently.

Q804. Poor conductors (insulators) are:

(a) Wood, rubber, glass ✅

(b) Copper

(d) None

Explanation: Lack of free electrons makes them poor conductors.

Q805. Thermal conductivity is:

(a) Measure of ability to conduct heat ✅

(b) Measure of ability to store heat

(d) None

Explanation: Higher conductivity → faster heat transfer.

Q806. Convection is:

(a) Heat transfer by movement of fluids ✅

(b) Heat transfer in solids

(d) None

Explanation: Fluid motion carries heat. Example: boiling water.

Q807. Natural convection occurs due to:

(a) Density differences caused by temperature ✅

(b) External pump

(d) None

Explanation: Hot fluid rises, cold fluid sinks, creating circulation.

Q808. Forced convection occurs due to:

(a) External agents like fans or pumps ✅

(b) Natural density differences

(d) None

Explanation: External force drives fluid motion.

Q809. Radiation is:

(a) Heat transfer by electromagnetic waves ✅

(b) Heat transfer by conduction

(d) None

Explanation: Does not require medium. Example: sunlight reaching Earth.

Q810. Radiant energy depends on:

(a) Temperature of body ✅

(b) Pressure

(d) None

Explanation: Hotter bodies emit more radiation.

Q811. Stefan-Boltzmann law states:

(a) E ∝ T⁴ ✅

(b) E ∝ T²

(d) None

Explanation: Radiant energy per unit area proportional to fourth power of temperature.

Q812. Perfect absorber and emitter of radiation is:

(a) Black body ✅

(b) White body

(d) None

Explanation: Absorbs all incident radiation, emits maximum possible.

Q813. Emissivity is:

(a) Ratio of radiation emitted by body to black body ✅

(b) Ratio of conduction to convection

(d) None

Explanation: Measures efficiency of radiation emission.

Q814. Greenhouse effect occurs due to:

(a) Trapping of infrared radiation ✅

(b) Trapping of ultraviolet radiation

(d) None

Explanation: Atmosphere traps heat, warming Earth.

Q815. Heat exchanger works on:

(a) Transfer of heat between two fluids ✅

(b) Transfer of heat between solid and fluid only

(d) None

Explanation: Used in power plants, refrigerators, air conditioners.

Q816. Thermal insulation reduces:

(a) Heat transfer ✅

(b) Heat generation

(d) None

Explanation: Materials like fiberglass, foam minimize conduction and convection.

Q817. Newton’s law of cooling states:

(a) Rate of cooling ∝ temperature difference ✅

(b) Rate of cooling ∝ pressure difference

(d) None

Explanation: dT/dt ∝ (T – Tₐ). Cooling faster when difference is larger.

Q818. Heat transfer in vacuum occurs by:

(a) Radiation only ✅

(b) Conduction

(d) None

Explanation: No medium for conduction or convection.

Q819. Conduction equation is:

(a) Q = (kAΔT·t)/d ✅

(b) Q = mcΔT

(d) None

Explanation: Fourier’s law of heat conduction.

Q820. Convection heat transfer depends on:

(a) Fluid velocity and properties ✅

(b) Solid properties only

(d) None

Explanation: Faster fluid motion → higher heat transfer.

Q821. Radiation depends on:

(a) Temperature, surface area, emissivity ✅

(b) Pressure

(d) None

Explanation: Hotter, larger, darker surfaces radiate more.

Q822. Heat transfer coefficient measures:

(a) Rate of heat transfer per unit area per unit temperature difference ✅

(b) Rate of work done

(d) None

Explanation: Important in convection calculations.

Q823. Applications of conduction include:

(a) Cooking utensils, heat sinks ✅

(b) Fans

(d) None

Explanation: Metals conduct heat quickly for practical use.

Q824. Applications of convection include:

(a) Heating water, atmospheric circulation ✅

(b) Mirrors

(d) None

Explanation: Convection currents drive weather and boiling.

Q825. Applications of radiation include:

(a) Solar heating, infrared devices ✅

(b) Electric circuits

(d) None

Explanation: Radiation transfers energy without medium.

Q826. Electrostatics deals with:

(a) Charges at rest ✅

(b) Charges in motion

(d) None

Explanation: Studies forces, fields, and potentials due to stationary charges.

Q827. Coulomb’s law states:

(a) F ∝ q₁q₂/r² ✅

(b) F ∝ q₁q₂r²

(d) None

Explanation: Force between two charges is proportional to product of charges and inversely proportional to square of distance.

Q828. Unit of charge is:

(a) Coulomb ✅

(b) Volt

(d) None

Explanation: 1 C = charge transported by 1 A current in 1 second.

Q829. Electric field is:

(a) Force per unit charge ✅

(b) Charge per unit force

(d) None

Explanation: E = F/q. Vector quantity.

Q830. Electric field lines represent:

(a) Direction of force on positive charge ✅

(b) Direction of force on negative charge

(d) None

Explanation: Lines show field direction and strength.

Q831. Electric potential is:

(a) Work done per unit charge ✅

(b) Force per unit charge

(d) None

Explanation: V = W/q. Scalar quantity.

Q832. Unit of potential is:

(a) Volt ✅

(b) Ampere

(d) None

Explanation: 1 V = 1 J/C.

Q833. Equipotential surface is:

(a) Surface with constant potential ✅

(b) Surface with varying potential

(d) None

Explanation: No work done moving charge along equipotential.

Q834. Electric dipole consists of:

(a) Two equal and opposite charges separated by distance ✅

(b) Two equal charges

(d) None

Explanation: Dipole moment p = q·d.

Q835. Dipole moment is:

(a) Product of charge and separation distance ✅

(b) Ratio of charge and distance

(d) None

Explanation: Vector quantity directed from negative to positive charge.

Q836. Capacitance is:

(a) Ability to store charge ✅

(b) Ability to store current

(d) None

Explanation: C = Q/V. Measured in farads.

Q837. Unit of capacitance is:

(a) Farad ✅

(b) Volt

(d) None

Explanation: 1 F = 1 C/V.

Q838. Capacitance of parallel plate capacitor:

(a) C = ε₀A/d ✅

(b) C = d/ε₀A

(d) None

Explanation: Depends on plate area and separation.

Q839. Dielectric increases capacitance because:

(a) Reduces effective electric field ✅

(b) Increases separation

(d) None

Explanation: Polarization reduces potential difference, increasing capacitance.

Q840. Energy stored in capacitor:

(a) U = ½CV² ✅

(b) U = CV²

(d) None

Explanation: Energy stored in electric field between plates.

Q841. Capacitors in series have:

(a) 1/Ceq = 1/C₁ + 1/C₂ + … ✅

(b) Ceq = C₁ + C₂

(d) None

Explanation: Equivalent capacitance smaller than smallest capacitor.

Q842. Capacitors in parallel have:

(a) Ceq = C₁ + C₂ + … ✅

(b) 1/Ceq = 1/C₁ + 1/C₂

(d) None

Explanation: Equivalent capacitance is sum of individual capacitances.

Q843. Electric flux is:

(a) Number of field lines through surface ✅

(b) Number of charges

(d) None

Explanation: Φ = E·A cosθ. Scalar quantity.

Q844. Gauss’s law states:

(a) Φ = q/ε₀ ✅

(b) Φ = qε₀

(d) None

Explanation: Electric flux through closed surface proportional to enclosed charge.

Q845. Gauss’s law is useful for:

(a) Symmetrical charge distributions ✅

(b) Random distributions

Explanation: Simplifies field calculations for spheres, cylinders, planes.

Q846. Electric field inside conductor is:

(a) Zero ✅

(b) Maximum

(d) None

Explanation: Charges reside on surface, canceling internal field.

Q847. Potential inside conductor is:

(a) Constant ✅

(b) Varies

(d) None

Explanation: Same everywhere inside conductor.

Q848. Lightning conductor works on:

(a) Providing path for discharge to ground ✅

(b) Storing charge

(d) None

Explanation: Protects buildings by safely conducting charges.

Q849. Capacitors are used in:

(a) Energy storage, filters, tuning circuits ✅

(b) Cooking

(d) None

Explanation: Essential in electronics for timing and smoothing signals.

Q850. Electrostatics overall studies:

(a) Electric charges, fields, potentials, capacitors ✅

(b) Magnetic fields only

(d) None

Explanation: Fundamental branch of physics dealing with stationary charges.

Q851. Current electricity deals with:

(a) Charges in motion ✅

(b) Charges at rest

(d) None

Explanation: Studies flow of electric charges through conductors.

Q852. Electric current is:

(a) Rate of flow of charge ✅

(b) Amount of charge

(d) None

Explanation: I = Q/t. Measured in amperes.

Q853. Conventional current flows:

(a) From positive to negative ✅

(b) From negative to positive

(d) None

Explanation: Defined opposite to electron flow.

Q854. Ohm’s law states:

(a) V = IR ✅

(b) V = I/R

(d) None

Explanation: Voltage across conductor proportional to current.

Q855. Resistance depends on:

(a) Length, area, material ✅

(b) Voltage

(d) None

Explanation: R = ρL/A. Longer wire → higher resistance.

Q856. Unit of resistance is:

(a) Ohm ✅

(b) Volt

(d) None

Explanation: 1 Ω = 1 V/A.

Q857. Conductance is:

(a) Reciprocal of resistance ✅

(b) Product of resistance

(d) None

Explanation: G = 1/R. Measured in siemens.

Q858. Resistivity depends on:

(a) Material ✅

(b) Length

(d) None

Explanation: Intrinsic property of material, independent of dimensions.

Q859. Resistance of wire increases with:

(a) Temperature (for metals) ✅

(b) Decrease in temperature

(d) None

Explanation: More collisions of electrons at higher temperature.

Q860. Superconductors have resistance:

(a) Zero below critical temperature ✅

(b) Infinite

(d) None

Explanation: Exhibit perfect conductivity.

Q861. Series combination of resistors:

(a) R = R₁ + R₂ + … ✅

(b) 1/R = 1/R₁ + 1/R₂

(d) None

Explanation: Equivalent resistance is sum of resistances.

Q862. Parallel combination of resistors:

(a) 1/R = 1/R₁ + 1/R₂ + … ✅

(b) R = R₁ + R₂

(d) None

Explanation: Equivalent resistance smaller than smallest resistor.

Q863. Electric power is:

(a) P = VI ✅

(b) P = V/I

(d) None

Explanation: Rate of energy consumption. Also P = I²R or V²/R.

Q864. Unit of power is:

(a) Watt ✅

(b) Volt

(d) None

Explanation: 1 W = 1 J/s.

Q865. Electric energy consumed is:

(a) E = Pt ✅

(b) E = P/t

(d) None

Explanation: Measured in kilowatt-hour (kWh).

Q866. Household electricity is measured in:

(a) Kilowatt-hour ✅

(b) Joule

(d) None

Explanation: 1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J.

Q867. Fuse works on:

(a) Heating effect of current ✅

(b) Magnetic effect

(d) None

Explanation: Melts when current exceeds safe limit, protecting circuit.

Q868. Electric cell converts:

(a) Chemical energy into electrical energy ✅

(b) Electrical into chemical

(d) None

Explanation: Basis of batteries.

Q869. Primary cell is:

(a) Non-rechargeable ✅

(b) Rechargeable

(d) None

Explanation: Example: dry cell.

Q870. Secondary cell is:

(a) Rechargeable ✅

(b) Non-rechargeable

(d) None

Explanation: Example: lead-acid battery.

Q871. Heating effect of current is given by:

(a) H = I²Rt ✅

(b) H = IRt

(d) None

Explanation: Joule’s law of heating.

Q872. Applications of heating effect include:

(a) Electric heater, bulb, fuse ✅

(b) Electric motor

(d) None

Explanation: Devices convert electrical energy into heat.

Q873. Magnetic effect of current discovered by:

(a) Oersted ✅

(b) Faraday

(d) None

Explanation: Current-carrying wire produces magnetic field.

Q874. Applications of magnetic effect include:

(a) Electromagnets, motors ✅

(b) Heaters

(d) None

Explanation: Used in machines and relays.

Q875. Current electricity overall studies:

(a) Flow of charges, resistance, circuits, applications ✅

(b) Charges at rest

(d) None

Explanation: Fundamental branch of physics for electrical systems.

Q876. Magnetism deals with:

(a) Properties of magnets and magnetic fields ✅

(b) Properties of charges at rest

(d) None

Explanation: Studies forces of attraction/repulsion and field interactions.

Q877. Magnetic poles always exist:

(a) In pairs (north and south) ✅

(b) Singly

(d) None

Explanation: Isolated magnetic monopoles do not exist in nature.

Q878. Magnetic field is:

(a) Region where magnetic force acts ✅

(b) Region where electric force acts

(d) None

Explanation: Represented by field lines around magnets or currents.

Q879. Magnetic field lines are:

(a) Closed continuous loops ✅

(b) Open lines

(d) None

Explanation: Always emerge from north pole and enter south pole.

Q880. Earth’s magnetism is due to:

(a) Currents in molten iron core ✅

(b) Electric charges at rest

(d) None

Explanation: Dynamo effect in Earth’s core generates magnetic field.

Q881. Magnetic declination is:

(a) Angle between geographic north and magnetic north ✅

(b) Angle between latitude and longitude

(d) None

Explanation: Varies with location on Earth.

Q882. Magnetic inclination (dip) is:

(a) Angle between magnetic field and horizontal ✅

(b) Angle between magnetic field and vertical

(d) None

Explanation: Indicates tilt of Earth’s magnetic field.

Q883. Magnetic materials are classified as:

(a) Diamagnetic, paramagnetic, ferromagnetic ✅

(b) Conductors, insulators

(d) None

Explanation: Based on response to external magnetic field.

Q884. Diamagnetic materials:

(a) Weakly repelled by magnetic field ✅

(b) Strongly attracted

(d) None

Explanation: Examples: copper, bismuth.

Q885. Paramagnetic materials:

(a) Weakly attracted by magnetic field ✅

(b) Strongly repelled

(d) None

Explanation: Examples: aluminum, platinum.

Q886. Ferromagnetic materials:

(a) Strongly attracted by magnetic field ✅

(b) Weakly repelled

(d) None

Explanation: Examples: iron, cobalt, nickel.

Q887. Electromagnetism discovered by:

(a) Oersted ✅

(b) Faraday

(d) None

Explanation: Current-carrying conductor produces magnetic field.

Q888. Right-hand thumb rule is used to:

(a) Find direction of magnetic field around conductor ✅

(b) Find direction of current

(d) None

Explanation: Thumb = current, curled fingers = field direction.

Q889. Magnetic field inside solenoid is:

(a) Uniform ✅

(b) Non-uniform

(d) None

Explanation: Solenoid produces strong uniform field inside.

Q890. Electromagnet is:

(a) Magnet produced by current ✅

(b) Natural magnet

(d) None

Explanation: Coil with current produces temporary magnetism.

Q891. Strength of electromagnet increases with:

(a) More turns and higher current ✅

(b) Less turns

(d) None

Explanation: Magnetic field proportional to NI (ampere-turns).

Q892. Faraday’s law of electromagnetic induction states:

(a) Induced emf ∝ rate of change of flux ✅

(b) Induced emf ∝ flux

(d) None

Explanation: emf = –dΦ/dt. Basis of generators.

Q893. Lenz’s law states:

(a) Induced current opposes cause producing it ✅

(b) Induced current aids cause

(d) None

Explanation: Ensures conservation of energy.

Q894. Fleming’s right-hand rule is used for:

(a) Generators ✅

(b) Motors

(d) None

Explanation: Thumb = motion, forefinger = field, middle finger = current.

Q895. Fleming’s left-hand rule is used for:

(a) Motors ✅

(b) Generators

(d) None

Explanation: Thumb = force, forefinger = field, middle finger = current.

Q896. Transformer works on:

(a) Electromagnetic induction ✅

(b) Electrostatics

(d) None

Explanation: Transfers AC voltage between coils.

Q897. Step-up transformer increases:

(a) Voltage ✅

(b) Current

(d) None

Explanation: Secondary voltage > primary voltage.

Q898. Step-down transformer decreases:

(a) Voltage ✅

(b) Current

(d) None

Explanation: Secondary voltage < primary voltage.

Q899. Applications of electromagnetism include:

(a) Motors, generators, transformers ✅

(b) Cooking

(d) None

Explanation: Basis of modern electrical technology.

Q900. Magnetism & electromagnetism overall study:

(a) Magnetic fields, materials, induction, devices ✅

(b) Electrostatics only

(d) None

Explanation: Fundamental branch of physics for electricity and magnetism.

Q901. Electromagnetic induction is:

(a) Production of emf due to changing magnetic flux ✅

(b) Production of emf due to static charges

(d) None

Explanation: Faraday’s law governs induction: emf = –dΦ/dt.

Q902. Faraday’s first law states:

(a) Changing magnetic flux induces emf ✅

(b) Constant flux induces emf

(d) None

Explanation: Basis of generators and transformers.

Q903. Faraday’s second law states:

(a) Induced emf ∝ rate of change of flux ✅

(b) Induced emf ∝ flux itself

(d) None

Explanation: Quantifies induced emf.

Q904. Lenz’s law states:

(a) Induced current opposes cause producing it ✅

(b) Induced current aids cause

(d) None

Explanation: Ensures conservation of energy.

Q905. Fleming’s right-hand rule is used for:

(a) Generators ✅

(b) Motors

(d) None

Explanation: Thumb = motion, forefinger = field, middle finger = current.

Q906. Fleming’s left-hand rule is used for:

(a) Motors ✅

(b) Generators

(d) None

Explanation: Thumb = force, forefinger = field, middle finger = current.

Q907. Self-induction is:

(a) Induced emf in coil due to change in its own current ✅

(b) Induced emf in another coil

(d) None

Explanation: Property of coil opposing change in current.

Q908. Mutual induction is:

(a) Induced emf in one coil due to change in current in another ✅

(b) Induced emf in same coil

(d) None

Explanation: Basis of transformers.

Q909. Inductance is:

(a) Measure of opposition to change in current ✅

(b) Measure of opposition to steady current

(d) None

Explanation: L = Φ/I. Unit: Henry.

Q910. Alternating current (AC) is:

(a) Current changing direction periodically ✅

(b) Current constant in direction

(d) None

Explanation: AC varies sinusoidally with time.

Q911. Frequency of AC in India is:

(a) 50 Hz ✅

(b) 60 Hz

(d) None

Explanation: Standard frequency of power supply.

Q912. Frequency of AC in USA is:

(a) 60 Hz ✅

(b) 50 Hz

(d) None

Explanation: Standard frequency of power supply.

Q913. RMS value of AC is:

(a) Effective value producing same heating as DC ✅

(b) Peak value

(d) None

Explanation: Irms = I₀/√2.

Q914. Average value of AC over half cycle:

(a) Iavg = (2/π) I₀ ✅

(b) Iavg = I₀/√2

(d) None

Explanation: Derived from integration over half cycle.

Q915. Power in AC circuit is:

(a) P = VI cos φ ✅

(b) P = VI

(d) None

Explanation: Depends on phase angle between voltage and current.

Q916. Power factor is:

(a) cos φ ✅

(b) sin φ

(d) None

Explanation: Ratio of true power to apparent power.

Q917. Inductive reactance is:

(a) XL = ωL ✅

(b) XL = 1/ωL

(d) None

Explanation: Opposition offered by inductor to AC.

Q918. Capacitive reactance is:

(a) XC = 1/ωC ✅

(b) XC = ωC

(d) None

Explanation: Opposition offered by capacitor to AC.

Q919. Impedance in AC circuit is:

(a) Z = √(R² + (XL – XC)²) ✅

(b) Z = R + XL + XC

(d) None

Explanation: Effective opposition to AC.

Q920. Resonance occurs when:

(a) XL = XC ✅

(b) XL > XC

(d) None

Explanation: Circuit impedance minimum, current maximum.

Q921. Resonant frequency is:

(a) f = 1/(2π√LC) ✅

(b) f = 1/(2πLC)

(d) None

Explanation: Frequency at which resonance occurs.

Q922. Transformer works on:

(a) Electromagnetic induction ✅

(b) Electrostatics

(d) None

Explanation: Transfers AC voltage between coils.

Q923. Step-up transformer increases:

(a) Voltage ✅

(b) Current

(d) None

Explanation: Secondary voltage > primary voltage.

Q924. Step-down transformer decreases:

(a) Voltage ✅

(b) Current

(d) None

Explanation: Secondary voltage < primary voltage.

Q925. Applications of AC include:

(a) Power supply, motors, transformers ✅

(b) Cooking only

(d) None

Explanation: AC is backbone of modern electrical systems.

Q926. Diode is:

(a) Device allowing current in one direction ✅

(b) Device allowing current both ways

(d) None

Explanation: Semiconductor diode conducts in forward bias, blocks in reverse bias.

Q927. Forward bias of diode means:

(a) Positive terminal to p-side, negative to n-side ✅

(b) Positive to n-side

(d) None

Explanation: Reduces barrier potential, allowing current flow.

Q928. Reverse bias of diode means:

(a) Positive terminal to n-side, negative to p-side ✅

(b) Positive to p-side

(d) None

Explanation: Increases barrier potential, blocks current.

Q929. Zener diode is used for:

(a) Voltage regulation ✅

(b) Current amplification

(d) None

Explanation: Operates in breakdown region to maintain constant voltage.

Q930. LED stands for:

(a) Light Emitting Diode ✅

(b) Light Energy Device

(d) None

Explanation: Emits light when forward biased.

Q931. Photodiode works on:

(a) Conversion of light into current ✅

(b) Conversion of current into light

(d) None

Explanation: Used in sensors and solar cells.

Q932. Transistor is used as:

(a) Amplifier and switch ✅

(b) Only resistor

(d) None

Explanation: Controls current flow, amplifies signals.

Q933. Transistor has:

(a) Three terminals: emitter, base, collector ✅

(b) Two terminals

(d) None

Explanation: Basic building block of electronics.

Q934. NPN transistor has:

(a) Two n-type and one p-type layers ✅

(b) Two p-type and one n-type

(d) None

Explanation: Common transistor type used in circuits.

Q935. PNP transistor has:

(a) Two p-type and one n-type layers ✅

(b) Two n-type and one p-type

(d) None

Explanation: Current flows from emitter to collector via base.

Q936. Logic gates are:

(a) Digital circuits performing logical operations ✅

(b) Analog circuits

(d) None

Explanation: Basic building blocks of digital electronics.

Q937. AND gate output is:

(a) 1 only if both inputs are 1 ✅

(b) 1 if any input is 1

(d) None

Explanation: Logical multiplication.

Q938. OR gate output is:

(a) 1 if any input is 1 ✅

(b) 1 only if both inputs are 1

(d) None

Explanation: Logical addition.

Q939. NOT gate output is:

(a) Inverse of input ✅

(b) Same as input

(d) None

Explanation: Logical negation.

Q940. NAND gate output is:

(a) Inverse of AND gate ✅

(b) Inverse of OR gate

(d) None

Explanation: Universal gate, can implement all logic functions.

Q941. NOR gate output is:

(a) Inverse of OR gate ✅

(b) Inverse of AND gate

(d) None

Explanation: Universal gate, can implement all logic functions.

Q942. XOR gate output is:

(a) 1 if inputs are different ✅

(b) 1 if inputs are same

(d) None

Explanation: Exclusive OR operation.

Q943. XNOR gate output is:

(a) 1 if inputs are same ✅

(b) 1 if inputs are different

(d) None

Explanation: Exclusive NOR operation.

Q944. Integrated circuit (IC) is:

(a) Circuit fabricated on semiconductor chip ✅

(b) Circuit made of discrete components

(d) None

Explanation: Miniaturized electronic circuit.

Q945. Microprocessor is:

(a) CPU on a single chip ✅

(b) Memory device

(d) None

Explanation: Performs arithmetic and logic operations.

Q946. Microcontroller is:

(a) CPU with memory and I/O on chip ✅

(b) Only CPU

(d) None

Explanation: Used in embedded systems.

Q947. Communication system requires:

(a) Transmitter, channel, receiver ✅

(b) Only transmitter

(d) None

Explanation: Complete system for information transfer.

Q948. Modulation is:

(a) Superimposing signal on carrier wave ✅

(b) Removing carrier wave

(d) None

Explanation: Enables long-distance transmission.

Q949. Demodulation is:

(a) Extracting signal from carrier wave ✅

(b) Adding carrier wave

(d) None

Explanation: Receiver recovers original information.

Q950. Electronics & communication overall study:

(a) Devices, circuits, signals, transmission ✅

(b) Only optics

(d) None

Explanation: Foundation of modern technology and communication systems.

Q951. Nuclear physics deals with:

(a) Properties of atomic nucleus ✅

(b) Properties of electrons

(d) None

Explanation: Studies structure, forces, and reactions inside nucleus.

Q952. Radioactivity is:

(a) Spontaneous emission of particles/rays from unstable nuclei ✅

(b) Emission from stable nuclei

(d) None

Explanation: Discovered by Becquerel, explained by Curie.

Q953. Types of radioactive decay are:

(a) Alpha, beta, gamma ✅

(b) Only alpha

(d) None

Explanation: Different emissions reduce instability of nucleus.

Q954. Alpha particle is:

(a) Helium nucleus (2p, 2n) ✅

(b) Electron

(d) None

Explanation: Heavy particle with +2 charge.

Q955. Beta particle is:

(a) Electron or positron emitted from nucleus ✅

(b) Proton

(d) None

Explanation: Results from neutron-proton conversion.

Q956. Gamma ray is:

(a) High-energy electromagnetic radiation ✅

(b) Proton

(d) None

Explanation: Emitted when nucleus shifts to lower energy state.

Q957. Half-life is:

(a) Time for half nuclei to decay ✅

(b) Time for all nuclei to decay

(d) None

Explanation: Characteristic property of radioactive isotope.

Q958. Unit of radioactivity is:

(a) Becquerel (Bq) ✅

(b) Joule

(d) None

Explanation: 1 Bq = 1 disintegration per second.

Q959. Nuclear fission is:

(a) Splitting of heavy nucleus into lighter nuclei ✅

(b) Combining of light nuclei

(d) None

Explanation: Releases large energy, used in reactors.

Q960. Example of fission fuel:

(a) Uranium-235 ✅

(b) Hydrogen

(d) None

Explanation: U-235 splits into smaller nuclei releasing energy.

Q961. Nuclear fusion is:

(a) Combining of light nuclei into heavier nucleus ✅

(b) Splitting of heavy nucleus

(d) None

Explanation: Powers the Sun, releases enormous energy.

Q962. Example of fusion reaction:

(a) Hydrogen nuclei forming helium ✅

(b) Uranium splitting

(d) None

Explanation: Occurs in stars, requires high temperature.

Q963. Energy released in nuclear reactions is given by:

(a) E = Δm c² ✅

(b) E = mc

(d) None

Explanation: Einstein’s mass-energy equivalence.

Q964. Nuclear reactor works on:

(a) Controlled fission ✅

(b) Fusion

(d) None

Explanation: Produces energy safely using moderators and control rods.

Q965. Moderator in reactor is:

(a) Slows down neutrons ✅

(b) Speeds up neutrons

(d) None

Explanation: Examples: graphite, heavy water.

Q966. Control rods in reactor are:

(a) Absorb excess neutrons ✅

(b) Emit neutrons

(d) None

Explanation: Examples: cadmium, boron.

Q967. Chain reaction is:

(a) Self-sustained fission process ✅

(b) Single fission

(d) None

Explanation: One fission produces neutrons causing further fission.

Q968. Nuclear fusion requires:

(a) Very high temperature and pressure ✅

(b) Low temperature

(d) None

Explanation: Overcomes Coulomb repulsion between nuclei.

Q969. Radiation hazards include:

(a) DNA damage, cancer ✅

(b) Improved health

(d) None

Explanation: Ionizing radiation harmful to living tissues.

Q970. Radiation protection uses:

(a) Lead shielding, distance, time control ✅

(b) Plastic shielding

(d) None

Explanation: Reduces exposure to harmful radiation.

Q971. Applications of radioisotopes include:

(a) Medicine, agriculture, industry ✅

(b) Cooking

(d) None

Explanation: Used in cancer treatment, food preservation, tracers.

Q972. Nuclear fusion is cleaner than fission because:

(a) Produces less radioactive waste ✅

(b) Produces more waste

(d) None

Explanation: Fusion products are generally stable.

Q973. Sun’s energy is due to:

(a) Nuclear fusion ✅

(b) Nuclear fission

(d) None

Explanation: Hydrogen nuclei fuse to form helium.

Q974. Nuclear power plants use:

(a) Fission ✅

(b) Fusion

(d) None

Explanation: Controlled fission generates electricity.

Q975. Nuclear physics overall studies:

(a) Nucleus, radioactivity, fission, fusion, applications ✅

(b) Only electrons

(d) None

Explanation: Fundamental branch of physics for energy and medical applications.

Q976. LASER stands for:

(a) Light Amplification by Stimulated Emission of Radiation ✅

(b) Light Absorption by Stimulated Emission

(d) None

Explanation: LASER produces coherent, monochromatic, and highly directional light.

Q977. Stimulated emission was proposed by:

(a) Einstein ✅

(b) Planck

(d) None

Explanation: Basis of laser operation, where photon stimulates emission of identical photon.

Q978. Properties of laser light are:

(a) Monochromatic, coherent, directional ✅

(b) Polychromatic, incoherent

(d) None

Explanation: Unique properties make lasers useful in science and technology.

Q979. Ruby laser uses:

(a) Crystalline ruby as medium ✅

(b) Gas

(d) None

Explanation: First successful laser, developed by Maiman in 1960.

Q980. Applications of lasers include:

(a) Medicine, communication, industry ✅

(b) Cooking

(d) None

Explanation: Used in surgery, fiber optics, cutting, welding.

Q981. Holography uses:

(a) Laser light for 3D imaging ✅

(b) Ordinary light

(d) None

Explanation: Records both intensity and phase of light.

Q982. Nanotechnology deals with:

(a) Materials at nanometer scale ✅

(b) Materials at meter scale

(d) None

Explanation: Manipulation of matter at atomic/molecular level.

Q983. Nanomaterials have:

(a) Unique optical, electrical, mechanical properties ✅

(b) Same as bulk materials

(d) None

Explanation: Properties change drastically at nanoscale.

Q984. Carbon nanotubes are:

(a) Cylindrical nanostructures of carbon ✅

(b) Spherical molecules

(d) None

Explanation: Exhibit high strength and conductivity.

Q985. Graphene is:

(a) Single layer of carbon atoms ✅

(b) Multiple layers

(d) None

Explanation: Two-dimensional material with remarkable properties.

Q986. Applications of nanotechnology include:

(a) Medicine, electronics, energy ✅

(b) Cooking

(d) None

Explanation: Used in drug delivery, sensors, batteries.

Q987. Quantum computer works on:

(a) Superposition and entanglement ✅

(b) Classical bits

(d) None

Explanation: Uses qubits for parallel computation.

Q988. Qubit is:

(a) Quantum bit with superposition states ✅

(b) Classical bit

(d) None

Explanation: Can represent 0 and 1 simultaneously.

Q989. Quantum entanglement is:

(a) Correlation between particles regardless of distance ✅

(b) Independent behavior

(d) None

Explanation: Basis for quantum communication.

Q990. Quantum cryptography ensures:

(a) Secure communication using quantum principles ✅

(b) Classical encryption

(d) None

Explanation: Exploits no-cloning theorem for security.

Q991. Semiconductor laser is:

(a) Laser using p-n junction ✅

(b) Laser using ruby

(d) None

Explanation: Compact, efficient, widely used in communication.

Q992. Fiber optic communication uses:

(a) Light signals through optical fibers ✅

(b) Radio waves

(d) None

Explanation: Provides high bandwidth and low loss.

Q993. Photonics is:

(a) Science of light-based technology ✅

(b) Science of sound

(d) None

Explanation: Includes lasers, fiber optics, optical computing.

Q994. Solar cell works on:

(a) Photovoltaic effect ✅

(b) Photoelectric effect only

(d) None

Explanation: Converts sunlight directly into electricity.

Q995. Efficiency of solar cell depends on:

(a) Material and sunlight intensity ✅

(b) Voltage only

(d) None

Explanation: Silicon commonly used, efficiency ~15–20%.

Q996. LED is used in:

(a) Displays, lighting ✅

(b) Heating

(d) None

Explanation: Energy-efficient light source.

Q997. Photodiode is used in:

(a) Light detection ✅

(b) Light emission

(d) None

Explanation: Converts light into electrical signal.

Q998. Quantum dot is:

(a) Nanoscale semiconductor particle ✅

(b) Large crystal

(d) None

Explanation: Exhibits quantum confinement effects.

Q999. Applications of quantum dots include:

(a) Displays, bio-imaging ✅

(b) Cooking

(d) None

Explanation: Emit tunable colors based on size.

Q1000. Modern physics applications overall study:

(a) Lasers, nanotechnology, quantum devices ✅

(b) Classical mechanics only

(d) None

Explanation: Cutting-edge technologies shaping future science and industry.

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