OAR OAR Mechanical Comprehension: Electricity 5 — Questions and Answers
Question 1: A wire carries 2A of current. How many coulombs of charge pass through in 30 seconds?
- 15C
- 32C
- 60C (Correct answer)
- 0.07C
Correct answer: 60C
Charge Q = I × t = 2A × 30s = 60C.
Question 2: What does increasing the cross-sectional area of a conductor do to its resistance?
- Increases resistance
- Decreases resistance (Correct answer)
- Has no effect
- Makes resistance nonlinear
Correct answer: Decreases resistance
A larger cross-section provides more parallel paths for electrons, lowering resistance like widening a pipe reduces flow resistance.
Question 3: A diode allows current to flow in which direction?
- In both directions equally
- Only from cathode to anode
- Only from anode to cathode (Correct answer)
- Only when AC is applied
Correct answer: Only from anode to cathode
A diode conducts current from anode to cathode (conventional current direction) and blocks reverse flow.
Question 4: What is the power factor in a purely resistive AC circuit?
- 0
- 0.5
- 0.707
- 1 (Correct answer)
Correct answer: 1
In a purely resistive circuit, voltage and current are in phase, giving a power factor of 1 (unity).
Question 5: Which law states that the total current entering a junction equals the total current leaving it?
- Ohm's Law
- Faraday's Law
- Kirchhoff's Current Law (Correct answer)
- Lenz's Law
Correct answer: Kirchhoff's Current Law
Kirchhoff's Current Law (KCL) states that charge conservation requires all current entering a node to equal all current leaving it.
Question 6: A step-up transformer increases voltage. What happens to the current on the secondary side (assuming ideal transformer)?
- Current increases proportionally
- Current decreases proportionally (Correct answer)
- Current stays the same
- Current becomes zero
Correct answer: Current decreases proportionally
An ideal transformer conserves power (P = VI), so if voltage increases, current must decrease by the same ratio.
Question 7: What is the equivalent capacitance of two 4μF capacitors connected in series?
- 8μF
- 4μF
- 2μF (Correct answer)
- 1μF
Correct answer: 2μF
For capacitors in series, 1/C = 1/4 + 1/4 = 2/4, so C = 2μF.
OAR OAR Mechanical Comprehension: Electricity 5
A wire carries 2A of current.
How many coulombs of charge pass through in 30 seconds?