Practice Test: Question Set - 03
1. A power supply produces a 0.6 W output with an input of 0.7 W. Its percentage of efficiency is
- (A) 8.57 %
- (B) 42.85 %
- (C) 4.28 %
- (D) 85.7 %
2. A 15 V source is connected across a 12 Ω resistor. How much energy is used in three minutes?
- (A) 938 Wh
- (B) 0.938 Wh
- (C) 56.25 Wh
- (D) 5.6 Wh
3. If you used 400 W of power for 30 h, you have used
- (A) 1.3 kWh
- (B) 13.3 kWh
- (C) 1.2 kWh
- (D) 12 kWh
4. How many watt-hours represent 65 W used for 18 h?
- (A) 11.7 Wh
- (B) 1,170 Wh
- (C) 11,700 Wh
- (D) 117,000 Wh
5. A 220 Ω resistor dissipates 3 W. The voltage is
- (A) 73.3 V
- (B) 2.5 V
- (C) 25.7 V
- (D) 257 V
6. A 6 V battery is connected to a 300 Ω load. Under these conditions, it is rated at 40 Ah. How long can it supply current to the load?
- (A) 1 h
- (B) 200 h
- (C) 2,000 h
- (D) 10 h
7. A 3.3 kΩ resistor dissipates 0.25 W. The current is
- (A) 8.7 mA
- (B) 87
mA
- (C) 8.7 µA
- (D) 8.7 A
8. When the current through a 12 kΩ resistor is 8 mA, the power is
- (A) 7.68 mW
- (B) 768 mW
- (C) 7.68 W
- (D) 76.8 W
9. Watt's law states the relationships of power to energy.
- (A) True
- (B) False
10. In 0.025 W, there are
- (A) 25 kW
- (B) 0.00025 mW
- (C) 2,500 µW
- (D) 25 mW
11. Energy equals power multiplied by time.
- (A) True
- (B) False
12. At the end of a 14 day period, your utility bill shows that you have used 18 kWh. What is your average daily power?
- (A) 1.286 kWh
- (B) 12.85 kWh
- (C) 535 kWh
- (D) 252 kWh
13. The power rating of a resistor determines the minimum power that it can handle safely.
- (A) True
- (B) False
14. If you used 600 W of power for 60 h, you have used
- (A) 36 kWh
- (B) 3.6 kWh
- (C) 10 kWh
- (D) 1 kWh
15. Power rating is related to resistance value.
- (A) True
- (B) False
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