NCERT BOOK CLASS 12TH PHYSICS MCQ
CHAPTER 3 : Current Electricity
IMPORTANT MCQ
1. What is the SI unit of Electric Current?
a) Volt
b) Ohm
c) Ampere
d) Watt
Answer: c) Ampere
2. The electric current flowing through a conductor is proportional to:
a) Resistance
b) Potential difference
c) Power
d) Energy
Answer: b) Potential difference
3. Ohm’s Law is valid for:
a) All conductors
b) Only metallic conductors
c) Only ohmic conductors
d) Semiconductors
Answer: c) Only ohmic conductors
4. The resistance of a wire depends on:
a) Length, cross-sectional area, and material
b) Only length
c) Only cross-sectional area
d) Only material
Answer: a) Length, cross-sectional area, and material
5. The unit of resistivity is:
a) Ohm-meter
b) Ohm/meter
c) Ohm-meter²
d) Ohm/meter²
Answer: a) Ohm-meter
6. As temperature increases, the resistivity of metals:
a) Increases
b) Decreases
c) Remains unchanged
d) First increases then decreases
Answer: a) Increases
7. Kirchhoff’s Current Law is based on the principle of:
a) Charge conservation
b) Energy conservation
c) Momentum conservation
d) Mass conservation
Answer: a) Charge conservation
8. When three resistors of 5Ω, 10Ω, and 15Ω are connected in series, the total resistance will be:
a) 30Ω
b) 5Ω
c) 2.7Ω
d) 10Ω
Answer: a) 30Ω
9. If three identical resistors are connected in parallel, the total resistance will be:
a) Equal to each resistor
b) Three times each resistor
c) One-third of each resistor
d) Square of each resistor
Answer: c) One-third of each resistor
10. A potentiometer is used to measure:
a) Current
b) Potential difference
c) Resistance
d) Power
Answer: b) Potential difference
11. A Wheatstone bridge is balanced when:
a) Current is zero
b) Potential difference is zero
c) There is no deflection in the galvanometer
d) All of the above
Answer: d) All of the above
12. The internal resistance of a cell depends on:
a) Concentration of the electrolyte
b) Material of the electrodes
c) Size of the cell
d) All of the above
Answer: d) All of the above
13. 1 kilowatt-hour (kWh) is equal to:
a) 3.6 × 10⁶ Joules
b) 1.6 × 10⁻¹⁹ Joules
c) 1.6 × 10⁻¹³ Joules
d) 1000 Joules
Answer: a) 3.6 × 10⁶ Joules
14. The unit of electric power is:
a) Volt
b) Watt
c) Joule
d) Coulomb
Answer: b) Watt
15. An electric heater works on the principle of:
a) Electromagnetic effect
b) Joule heating
c) Faraday effect
d) Seebeck effect
Answer: b) Joule heating
16. A thermocouple operates on the principle of:
a) Joule heating
b) Seebeck effect
c) Peltier effect
d) Thomson effect
Answer: b) Seebeck effect
17. The drift velocity of electrons in a conductor is proportional to:
a) Electric current
b) Potential difference
c) Resistance
d) Length of the conductor
Answer: a) Electric current
18. The rate of heat produced in a conductor of 2Ω resistance carrying 5A current is:
a) 10 W
b) 20 W
c) 50 W
d) 100 W
Answer: c) 50 W
19. The potential drop in an electric circuit is measured using:
a) Ammeter
b) Voltmeter
c) Galvanometer
d) Ohmmeter
Answer: b) Voltmeter
20. How is an ammeter connected in a circuit?
a) In parallel
b) In series
c) Either in series or parallel
d) Outside the circuit
Answer: b) In series
21. How is a voltmeter connected in a circuit?
a) In series
b) In parallel
c) In any configuration
d) Outside the circuit
Answer: b) In parallel
22. A 220V, 100W bulb is connected to a 110V source. Its power will be:
a) 100W
b) 50W
c) 25W
d) 200W
Answer: c) 25W
23. Who discovered the magnetic effect of electric current?
a) Ohm
b) Faraday
c) Oersted
d) Ampere
Answer: c) Oersted
24. The drift velocity of electrons in a conductor is inversely proportional to:
a) Cross-sectional area of the conductor
b) Number density of electrons
c) Length of the conductor
d) Electric current
Answer: a) Cross-sectional area of the conductor
25. The resistivity of copper is approximately:
a) 1.6 × 10⁻⁸ Ωm
b) 2.8 × 10⁻⁸ Ωm
c) 1.7 × 10⁻⁸ Ωm
d) 5.6 × 10⁻⁸ Ωm
Answer: c) 1.7 × 10⁻⁸ Ωm
26. The temperature coefficient of resistance is negative for:
a) Metal
b) Semiconductor
c) Insulator
d) Superconductor
Answer: b) Semiconductor
27. Kirchhoff’s Voltage Law is based on the principle of:
a) Charge conservation
b) Energy conservation
c) Momentum conservation
d) Mass conservation
Answer: b) Energy conservation
28. When three resistors of 2Ω, 4Ω, and 8Ω are connected in parallel, the total resistance will be:
a) 14Ω
b) 1.14Ω
c) 0.875Ω
d) 8/7Ω
Answer: d) 8/7Ω
29. If a wire is stretched to double its length, its new resistance will be:
a) The same
b) Double
c) Four times
d) Half
Answer: c) Four times
30. A potentiometer is better than a voltmeter because:
a) It is more sensitive
b) It does not draw current from the circuit
c) It has higher accuracy
d) All of the above
Answer: d) All of the above
31. In a series combination of cells:
a) Total potential difference increases
b) Internal resistance increases
c) Current capacity remains the same
d) All of the above
Answer: d) All of the above
32. In a parallel combination of cells:
a) Total potential difference remains the same
b) Current capacity increases
c) Internal resistance decreases
d) All of the above
Answer: d) All of the above
33. 1 electron volt (eV) is equal to:
a) 1.6 × 10⁻¹⁹ J
b) 3.6 × 10⁻¹⁹ J
c) 1.6 × 10⁻¹³ J
d) 1 J
Answer: a) 1.6 × 10⁻¹⁹ J
34. An electric fuse works on the principle of:
a) Electromagnetic induction
b) Joule heating
c) Seebeck effect
d) Electrolysis
Answer: b) Joule heating
35. An electric motor operates on the principle of:
a) Joule heating
b) Electromagnetic induction
c) Faraday’s law
d) Lorentz force
Answer: d) Lorentz force
36. The approximate value of electron drift velocity in a conductor is:
a) 10⁸ m/s
b) 10⁵ m/s
c) 10⁻³ m/s
d) 10⁻⁵ m/s
Answer: c) 10⁻³ m/s
37. The heat produced in a 5Ω resistor when a 3A current flows for 2 minutes is:
a) 900 J
b) 5400 J
c) 1800 J
d) 3600 J
Answer: b) 5400 J
38. The material used in the filament of an electric bulb is:
a) Copper
b) Tungsten
c) Iron
d) Nickel
Answer: b) Tungsten
39. The unit of current density is:
a) A/m
b) A/m²
c) A/m³
d) A·m
Answer: b) A/m²
40. The resistivity of a superconductor is:
a) Very high
b) Very low
c) Zero
d) Temperature-dependent
Answer: c) Zero
41. A meter bridge works on the principle of:
a) Ohm’s law
b) Wheatstone bridge
c) Kirchhoff’s law
d) Joule’s law
Answer: b) Wheatstone bridge
42. Power loss in an electric circuit is proportional to:
a) Current
b) Square of current
c) Resistance
d) Both (b) and (c)
Answer: d) Both (b) and (c)
43. The SI unit of electrical conductivity is:
a) Ohm⁻¹
b) Ohm⁻¹m⁻¹
c) Siemens
d) All of the above
Answer: d) All of the above
44. Nichrome is used in:
a) Electric heater
b) Electric motor
c) Transformer
d) Generator
Answer: a) Electric heater
45. The flow of electric current in a conductor is due to:
a) Motion of electrons
b) Motion of protons
c) Motion of neutrons
d) Motion of atoms
Answer: a) Motion of electrons
46. A thermocouple is used to measure:
a) Electric current
b) Temperature
c) Potential difference
d) Resistance
Answer: b) Temperature
47. The conventional direction of current is taken as:
a) Direction of electron flow
b) Direction of positive charge flow
c) Direction of proton flow
d) Direction of neutron flow
Answer: b) Direction of positive charge flow
48. The relation between current density (J) and drift velocity (v) in a conductor is:
a) J = nev
b) J = ne/v
c) J = ne²v
d) J = v/ne
Answer: a) J = nev
49. The gas filled in an electric bulb is:
a) Oxygen
b) Nitrogen
c) Argon
d) Both (b) and (c)
Answer: d) Both (b) and (c)
50. The resistance of an ammeter in a circuit should be:
a) Very high
b) Very low
c) Zero
d) Equal to the circuit resistance
Answer: b) Very low
51. In resistors connected in series in an electric circuit:
a) Current remains the same
b) Potential difference remains the same
c) Power remains the same
d) Energy remains the same
Answer: a) Current remains the same
52. In resistors connected in parallel:
a) Current remains the same
b) Potential difference remains the same
c) Resistance remains the same
d) Power remains the same
Answer: b) Potential difference remains the same
53. The heating effect of electric current depends on:
a) Current only
b) Resistance only
c) Both current and resistance
d) Time only
Answer: c) Both current and resistance
54. Which metal is used in an electric heater?
a) Copper
b) Aluminum
c) Nichrome
d) Gold
Answer: c) Nichrome
55. 1 Volt is defined as:
a) 1 Joule/Coulomb
b) 1 Coulomb/Joule
c) 1 Ohm×Ampere
d) 1 Ampere/Ohm
Answer: a) 1 Joule/Coulomb
56. The function of an electric fuse is to:
a) Increase current
b) Protect the circuit
c) Control potential difference
d) Increase power
Answer: b) Protect the circuit
57. The direction of electron drift velocity in a conductor is:
a) Same as the electric field
b) Opposite to the electric field
c) At 45° to the electric field
d) Random
Answer: b) Opposite to the electric field
58. Tungsten is used in electric bulbs because:
a) It has a high melting point
b) It is cheap
c) It is easily available
d) It has a good color
Answer: a) It has a high melting point
59. The relationship between conductivity (σ) and resistivity (ρ) is:
a) σ = 1/ρ
b) ρ = 1/σ
c) σ = ρ
d) σ = ρ²
Answer: a) σ = 1/ρ
60. The relationship between current density (J) and electric field (E) is:
a) J = σE
b) J = E/σ
c) J = σ/E
d) J = σ²E
Answer: a) J = σE
61. The approximate value of free electron number density in a conductor is:
a) 10²⁸ m⁻³
b) 10²⁰ m⁻³
c) 10¹⁰ m⁻³
d) 10⁵ m⁻³
Answer: a) 10²⁸ m⁻³
62. The correct formula(s) for electric power is/are:
a) P = VI
b) P = I²R
c) P = V²/R
d) All of the above
Answer: d) All of the above
63. The commercial unit of electrical energy is:
a) Watt
b) Joule
c) Kilowatt-hour (kWh)
d) Volt
Answer: c) Kilowatt-hour (kWh)
64. In a potentiometer, under null deflection condition:
a) No current is drawn from the cell
b) Current flows through the galvanometer
c) Current flows through the voltmeter
d) Current flows through the ammeter
Answer: a) No current is drawn from the cell
65. The formula for heat produced when current flows through a conductor is:
a) H = I²Rt
b) H = VIt
c) H = V²t/R
d) All of the above
Answer: d) All of the above
66. The chemical effect of electric current is observed in:
a) Electric motor
b) Electric heater
c) Electrolysis
d) Transformer
Answer: c) Electrolysis
67. The magnetic effect of electric current is observed in:
a) Electric bulb
b) Electric heater
c) Electric bell
d) Electric fuse
Answer: c) Electric bell
68. The heating effect of current is NOT used in:
a) Electric iron
b) Electric heater
c) Electric motor
d) Electric kettle
Answer: c) Electric motor
69. Electric current flows:
a) From high potential to low potential
b) From low potential to high potential
c) Between equal potentials
d) In any direction
Answer: a) From high potential to low potential
70. The function of resistance in an electric circuit is to:
a) Increase current
b) Limit current
c) Increase potential difference
d) Increase power
Answer: b) Limit current
71. The device used to measure electric current is:
a) Voltmeter
b) Ammeter
c) Galvanometer
d) Ohmmeter
Answer: b) Ammeter
72. The device used to measure potential difference is:
a) Ammeter
b) Voltmeter
c) Ohmmeter
d) Wattmeter
Answer: b) Voltmeter
73. The device used to measure resistance is:
a) Ammeter
b) Voltmeter
c) Ohmmeter
d) Galvanometer
Answer: c) Ohmmeter
74. The device used to measure power in an electric circuit is:
a) Wattmeter
b) Voltmeter
c) Ammeter
d) Ohmmeter
Answer: a) Wattmeter
75. The resistivity of a conductor depends on:
a) Material of the conductor
b) Temperature of the conductor
c) Dimensions of the conductor
d) Both (a) and (b)
Answer: d) Both (a) and (b)