OAR OAR Mechanical Comprehension: Electricity 2 — Questions and Answers
Question 1: Two resistors of 6Ω and 12Ω are connected in parallel. What is the equivalent resistance?
- 18Ω
- 4Ω (Correct answer)
- 9Ω
- 2Ω
Correct answer: 4Ω
For parallel resistors, 1/R = 1/6 + 1/12 = 3/12, so R = 4Ω.
Question 2: A 100W light bulb operates on a 120V circuit. What current does it draw?
- 0.48A
- 0.83A (Correct answer)
- 1.2A
- 12A
Correct answer: 0.83A
Using P = IV, I = P/V = 100/120 ≈ 0.83A.
Question 3: What happens to the total resistance when additional resistors are added in series?
- It decreases
- It stays the same
- It increases (Correct answer)
- It becomes zero
Correct answer: It increases
In a series circuit, total resistance is the sum of all individual resistances, so it always increases as more resistors are added.
Question 4: Which material is the best electrical conductor?
- Glass
- Rubber
- Silver (Correct answer)
- Silicon
Correct answer: Silver
Silver has the highest electrical conductivity of all metals, making it the best conductor.
Question 5: A circuit has a 9V battery and a single 3Ω resistor. What power is dissipated?
- 3W
- 27W (Correct answer)
- 6W
- 81W
Correct answer: 27W
Using P = V²/R = 81/3 = 27W.
Question 6: What does a capacitor do in a DC circuit once fully charged?
- Allows full current to flow
- Blocks current flow (Correct answer)
- Increases current
- Acts as a resistor
Correct answer: Blocks current flow
A fully charged capacitor blocks DC current because its electric field opposes additional charge movement.
Question 7: If voltage doubles while resistance stays constant, what happens to power?
- Power doubles
- Power halves
- Power quadruples (Correct answer)
- Power stays the same
Correct answer: Power quadruples
Since P = V²/R, doubling voltage squares the effect, so power quadruples.
OAR OAR Mechanical Comprehension: Electricity 2
Two resistors of 6Ω and 12Ω are connected in parallel.
What is the equivalent resistance?