Energy and Power problems
- 1. A 3.3 kΩ resistor dissipates 0.25 W. The current is
Options- A. 8.7 mA
- B. 87 mA
- C. 8.7 µA
- D. 8.7 A Discuss
Correct Answer: 8.7 mA
Explanation:
W = I2R
I = square root(W/R)
= square root( 0.25/(3.3x1000) )
= 0.0087038828
= 8.7 mA
I = square root(W/R)
= square root( 0.25/(3.3x1000) )
= 0.0087038828
= 8.7 mA
- 2. A given power supply is capable of providing 6 A for 3.5 h. Its ampere-hour rating is
Options- A. 0.58 Ah
- B. 2.1 Ah
- C. 21 Ah
- D. 58 Ah Discuss
Correct Answer: 21 Ah
- 3. At the end of a 14 day period, your utility bill shows that you have used 18 kWh. What is your average daily power?
Options- A. 1.286 kWh
- B. 12.85 kWh
- C. 535 kWh
- D. 252 kWh Discuss
Correct Answer: 1.286 kWh
- 4. Three hundred joules of energy are consumed in 15 s. The power is
Options- A. 2,000 W
- B. 2 W
- C. 20 W
- D. 200 W Discuss
Correct Answer: 20 W
- 5. For 12 V and 40 mA, the power is
Options- A. 480 mW
- B. 0.480 W
- C. 480,000 µW
- D. all of the above Discuss
Correct Answer: all of the above
- 6. When the pointer of an analog ohmmeter reads close to zero, the resistor being measured is
Options- A. overheated
- B. shorted
- C. open
- D. reversed Discuss
Correct Answer: shorted
- 7. If it takes 400 ms to use 12,000 J of energy, the power is
Options- A. 30 kW
- B. 30 W
- C. 3 W
- D. 300 kW Discuss
Correct Answer: 30 kW
- 8. A 33 Ω half-watt resistor and a 330 Ω half-watt resistor are connected across a 12 V source. Which one(s) will overheat?
Options- A. 33 Ω
- B. 330 Ω
- C. both resistors
- D. neither resistor Discuss
Correct Answer: neither resistor
- 9. The power rating of a carbon-composition resistor that is to handle up to 1.2 W should be
Options- A. 2 W
- B. 1 W
- C. 5 W
- D. 0.5 W Discuss
Correct Answer: 2 W
- 10. When the current through a 12 kΩ resistor is 8 mA, the power is
Options- A. 7.68 mW
- B. 768 mW
- C. 7.68 W
- D. 76.8 W Discuss
Correct Answer: 768 mW
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