GROL Electrical Principles and Units 2 — Questions and Answers
Question 1: A resistor dissipates 50 watts with 10 volts across it. What is the current through the resistor?
- 0.5 A
- 5 A (Correct answer)
- 50 A
- 500 A
Correct answer: 5 A
Using P = IV, rearranged as I = P/V = 50/10 = 5 A.
Question 2: Three resistors of 10 Ω, 20 Ω, and 30 Ω are connected in series. What is the total resistance?
- 5.45 Ω
- 18.18 Ω
- 60 Ω (Correct answer)
- 600 Ω
Correct answer: 60 Ω
Series resistances add directly: 10 + 20 + 30 = 60 Ω.
Question 3: Two 100-ohm resistors are connected in parallel. What is the total resistance?
- 200 Ω
- 100 Ω
- 50 Ω (Correct answer)
- 25 Ω
Correct answer: 50 Ω
For two equal parallel resistors, Rp = R/2 = 100/2 = 50 Ω.
Question 4: A 2 kΩ and 8 kΩ resistor are connected in series across 100 V as a voltage divider. What is the voltage across the 2 kΩ resistor?
- 80 V
- 50 V
- 25 V
- 20 V (Correct answer)
Correct answer: 20 V
V = Vsupply × R1/(R1+R2) = 100 × 2000/10000 = 20 V.
Question 5: A 12 V supply is connected to a 4 Ω and a 6 Ω resistor in parallel. What is the total current from the supply?
- 2 A
- 3 A
- 5 A (Correct answer)
- 10 A
Correct answer: 5 A
I1 = 12/4 = 3 A, I2 = 12/6 = 2 A; total current = 3 + 2 = 5 A.
Question 6: What is the power dissipated by a 470-ohm resistor carrying 20 mA?
- 9.4 mW
- 94 mW
- 188 mW (Correct answer)
- 940 mW
Correct answer: 188 mW
P = I²R = (0.02)² × 470 = 0.0004 × 470 = 0.188 W = 188 mW.
Question 7: Resistors R1 = 100 Ω and R2 = 200 Ω are connected in series across a 12 V supply. What is the voltage drop across R1?
- 4 V (Correct answer)
- 6 V
- 8 V
- 12 V
Correct answer: 4 V
V1 = 12 × 100/(100+200) = 12 × 1/3 = 4 V.
GROL Electrical Principles and Units 2
A resistor dissipates 50 watts with 10 volts across it.
What is the current through the resistor?