Energy and Power Electrical Engineering MCQ - ObjectiveBooks

# 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 Î© 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 Î© 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 Î© 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 kÎ© resistor dissipates 0.25 W. The current is
(A) 8.7 mA
(B) 87 mA
(C) 8.7 ÂµA
(D) 8.7 A

8. When the current through a 12 kÎ© 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 ÂµW
(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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