Chapter-3 Current Electricity — Online MCQ Test
PHYSICS · CLASS 12 SECOND PUC · Karnataka State Board
Practice Chapter-3 Current Electricity with a free chapter-wise online MCQ test.
This chapter covers: drift velocity - Ohm's law - resistance - V-I characteristics - Kirchhoff's laws - Wheatstone bridge - internal resistance.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-3 Current Electricity — Important Questions & Answers
Drift velocity is defined as:
- A. The average velocity acquired by free electrons in the direction of electric field
- B. The instantaneous velocity of electrons at any moment
- C. The velocity of electrons due to thermal motion
- D. The maximum velocity electrons can achieve
Answer: A. The average velocity acquired by free electrons in the direction of electric field
Drift velocity is the average velocity with which free electrons move in the direction opposite to the applied electric field in a conductor.
Drift velocity is the average velocity with which free electrons move in the direction opposite to the applied electric field in a conductor.
Ohm's law states that:
- A. V = IR
- B. V = I/R
- C. I = VR
- D. R = I/V
Answer: A. V = IR
Ohm's law mathematically expresses the relationship: Voltage = Current × Resistance, or V = IR, for an ohmic conductor at constant temperature.
Ohm's law mathematically expresses the relationship: Voltage = Current × Resistance, or V = IR, for an ohmic conductor at constant temperature.
The relationship between drift velocity (vd) and current (I) is:
- A. I ∝ vd
- B. I ∝ 1/vd
- C. I is independent of vd
- D. I ∝ vd²
Answer: A. I ∝ vd
Current is directly proportional to drift velocity: I = nAevd, where n is electron density, A is cross-sectional area, and e is electron charge.
Current is directly proportional to drift velocity: I = nAevd, where n is electron density, A is cross-sectional area, and e is electron charge.
A conductor has a resistance of 10Ω at 0°C. If its temperature coefficient of resistance is 0.005/°C, its resistance at 100°C will be approximately:
- A. 15Ω
- B. 10.5Ω
- C. 15Ω
- D. 20Ω
Answer: A. 15Ω
Using R = R₀(1 + αΔT), where R₀ = 10Ω, α = 0.005/°C, ΔT = 100°C: R = 10(1 + 0.005 × 100) = 10(1.5) = 15Ω.
Using R = R₀(1 + αΔT), where R₀ = 10Ω, α = 0.005/°C, ΔT = 100°C: R = 10(1 + 0.005 × 100) = 10(1.5) = 15Ω.
A battery with EMF E and negligible internal resistance is connected to a network of resistors. Using Kirchhoff's junction rule at a specific junction, if currents I₁ (3A entering), I₂ (5A leaving), and I₃ (unknown) meet, then I₃ is:
- A. 2A entering
- B. 8A leaving
- C. 2A leaving
- D. 8A entering
Answer: A. 2A entering
By Kirchhoff's junction rule: ΣIin = ΣIout. So 3A + I₃ = 5A, giving I₃ = 2A entering the junction.
By Kirchhoff's junction rule: ΣIin = ΣIout. So 3A + I₃ = 5A, giving I₃ = 2A entering the junction.