BMST Electrical Circuits and Ohm's Law 5 — Questions and Answers
Question 1: A fuse is rated at 5 A. What is its primary function in a circuit?
- Increase voltage
- Store electrical energy
- Protect against excessive current (Correct answer)
- Reduce resistance
Correct answer: Protect against excessive current
A fuse melts and breaks the circuit if current exceeds its rated value, protecting components.
Question 2: Three 12 Ω resistors are connected in parallel. What is the equivalent resistance?
- 1 Ω
- 4 Ω (Correct answer)
- 12 Ω
- 36 Ω
Correct answer: 4 Ω
For N equal resistors in parallel, R_eq = R/N = 12/3 = 4 Ω.
Question 3: How much energy does a 100 W appliance use in 2 hours?
- 50 J
- 200 J
- 720,000 J (Correct answer)
- 1,440,000 J
Correct answer: 720,000 J
Energy = Power × Time = 100 W × 7200 s = 720,000 J.
Question 4: Which circuit configuration ensures that all components receive the same voltage?
- Series circuit
- Parallel circuit (Correct answer)
- Short circuit
- Open circuit
Correct answer: Parallel circuit
In a parallel circuit, each branch is connected directly to the source, so all branches share the same voltage.
Question 5: A 5 Ω and 20 Ω resistor are in series with a 50 V source. What is the voltage drop across the 20 Ω resistor?
- 10 V
- 20 V
- 40 V (Correct answer)
- 50 V
Correct answer: 40 V
Total R = 25 Ω; I = 50/25 = 2 A; V = 2 × 20 = 40 V across the 20 Ω resistor.
Question 6: What is the relationship between resistance and the cross-sectional area of a conductor?
- Resistance increases as area increases
- Resistance decreases as area increases (Correct answer)
- Resistance is unaffected by area
- Resistance equals area squared
Correct answer: Resistance decreases as area increases
A larger cross-sectional area provides more paths for electrons, reducing resistance.
Question 7: A device draws 2 A at 110 V for 30 minutes. How many watt-hours of energy does it consume?
- 11 Wh
- 55 Wh
- 110 Wh (Correct answer)
- 220 Wh
Correct answer: 110 Wh
Power = I × V = 2 × 110 = 220 W; Energy = 220 W × 0.5 h = 110 Wh.
BMST Electrical Circuits and Ohm's Law 5
A fuse is rated at 5 A.
What is its primary function in a circuit?