30 most important MCQs with answers on the topic of *current electricity* for Class 12 Physics exam preparation
MCQs on Current Electricity
1. What is the rate of flow of electric charge through any cross-section of a conductor?
- (a) Electric flux
- (b) Electric potential
- (c) Electric current
- (d) Electric field
- *Answer: (c) Electric current
2. SI unit of electric current is:
- (a) Coulomb
- (b) Ampere
- (c) Volt
- (d) Ohm
- *Answer: (b) Ampere
3. What is the unit of conductance?
- (a) Dyne
- (b) Siemen
- (c) Ohm
- (d) Volt
- *Answer: (b) Siemen
4. In the series combination of two or more resistances, the current through each is:
- (a) Same
- (b) Different
- (c) Zero
- (d) None of these
- *Answer: (a) Same
5. How many different resistances are possible with two equal resistors?
- (a) 2
- (b) 3
- (c) 4
- (d) 5
- *Answer: (b) 3
6. Specific resistance of metals is mostly affected by:
- (a) Temperature
- (b) Pressure
- (c) Magnetic field
- (d) Volume
- *Answer: (a) Temperature
7. Drift velocity of electrons inside a conductor is:
- (a) Thermal speed
- (b) Average speed required by electron in any direction
- (c) Speed at which free electron emerges out
- (d) Average speed between collisions in the direction opposite to electric field
- *Answer: (d) Average speed between collisions opposite electric field
8. In a parallel combination of resistors, the effective resistance is:
- (a) Greater than any individual resistance
- (b) Less than smallest resistance
- (c) Equal to largest resistance
- (d) None
- *Answer: (b) Less than smallest resistance
9. Ohm's law states:
- (a) V ∝ I
- (b) V ∝ R
- (c) V = IR
- (d) Both (a) and (c)
- *Answer: (d) Both (a) and (c)
10. Electric current flows in a conductor from:
- (a) Higher potential to lower potential
- (b) Lower to higher
- (c) Both directions
- (d) None
- *Answer: (a) Higher to lower
11. The number of electrons constituting 1 ampere current:
- (a) 2.25 × 10¹⁸
- (b) 6.25 × 10¹⁸
- (c) 1.6 × 10⁻¹⁹
- (d) None
- *Answer: (b) 6.25 × 10¹⁸
12. In metallic conductors, current carriers are:
- (a) Positive ions
- (b) Negative ions
- (c) Electrons
- (d) Protons
- *Answer: (c) Electrons
13. In electrolytes, current carriers are:
- (a) Only electrons
- (b) Positive and negative ions
- (c) Only negative ions
- (d) Only positive ions
- *Answer: (b) Positive and negative ions
14. The dimensional formula of electric current is:
- (a) [M L T⁻²]
- (b) [M⁰ L⁰ T⁰ A¹]
- (c) [M L³ T⁰]
- (d) [M L² T⁻³]
- *Answer: (b) [M⁰ L⁰ T⁰ A¹]
15. The resistivity of a conductor depends on:
- (a) Temperature
- (b) Length
- (c) Area of cross-section
- (d) None
- *Answer: (a) Temperature
16. Kirchhoff’s first law is based on:
- (a) Conservation of energy
- (b) Conservation of charge
- (c) Conservation of mass
- (d) Conservation of potential
- *Answer: (b) Conservation of charge
17. Drift velocity is proportional to:
- (a) Electric field
- (b) Temperature
- (c) Resistance
- (d) Current
- *Answer: (a) Electric field
18. Which graph shows the variation of resistance with temperature for a metallic conductor?
- (a) Straight line
- (b) Exponential
- (c) Hyperbolic
- (d) Parabolic
- *Answer: (a) Straight line
19. Value of resistance when wire length doubled and area halved?
- (a) Four times
- (b) Twice
- (c) Half
- (d) Same
- *Answer: (a) Four times
20. A cell with emf ‘E’ and internal resistance ‘r’ is connected to external resistance ‘R’. Terminal voltage V when R increases:
- (a) Increases
- (b) Decreases
- (c) Remains same
- (d) First increases then decreases
- *Answer: (a) Increases
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Chapter wise Extra Q & A Sets (Physics, Class 12) |
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Electric Charges and Fields |
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Electrostatic Potential and Capacitance |
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Current Electricity |
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Moving Charges and Magnetism |
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Magnetism and Matter |
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Electromagnetic Induction |
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Alternating Current (AC) |
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Electromagnetic Waves |
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Ray Optics and Optical Instruments |
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Wave Optics |
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Dual Nature of Radiation and Matter |
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Atoms |
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Nuclei |
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Semiconductor Electronics: Materials, Devices and Simple Circuits |
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Communication System |
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21. Electrical energy is measured in:
- (a) Joule
- (b) Watt
- (c) Coulomb
- (d) Ohm
- *Answer: (a) Joule
22. Power dissipated in a resistor (R) with current (I):
- (a) P = I²R
- (b) P = IR
- (c) P = V/R
- (d) P = V²/I
- *Answer: (a) P = I²R
23. Which combination produces minimum resistance with resistors?
- (a) Series
- (b) Parallel
- (c) Both equal
- (d) None
- *Answer: (b) Parallel
24. The direction of conventional current in a conductor is:
- (a) Direction of flow of electrons
- (b) Opposite to electrons
- (c) Same as electron flow
- (d) Random
- *Answer: (b) Opposite to electrons
25. A fuse wire melts due to:
- (a) High resistance
- (b) Overload current
- (c) Excess voltage
- (d) None
- *Answer: (b) Overload current
26. Wheatstone bridge is used to measure:
- (a) Voltage
- (b) Current
- (c) Capacitance
- (d) Resistance
- *Answer: (d) Resistance
27. Resistance of a conductor is at minimum when:
- (a) Area is maximum, length is minimum
- (b) Area is minimum, length is maximum
- (c) Both are minimum
- (d) Both are maximum
- *Answer: (a) Area is maximum, length is minimum
28. The total current entering a junction equals total current leaving due to:
- (a) Kirchhoff’s Law
- (b) Ohm’s Law
- (c) Joule’s Law
- (d) Faraday’s Law
- *Answer: (a) Kirchhoff’s Law
29. Why is copper preferred for electrical wires?
- (a) Low resistivity
- (b) High resistivity
- (c) High cost
- (d) None
- *Answer: (a) Low resistivity
30. A device that converts electrical energy into heat:
- (a) Electric heater
- (b) Motor
- (c) Cell
- (d) Transformer
- *Answer: (a) Electric heater
