The power rating of a 470 ohm resistor carrying a current of 40 mA should be
- A. 1/4 W
- B. 1/2 W
- C. 2 W
- D. 1 W
Answer: D. 1 W
Explanation: $P = I^2R = (40\times 10^{-3})^2 \times 470 = 0.752$ watt. To safely handle this without burning out, the next standard power rating of 1 Watt should be used.