Question

An electric bulb rated 200 V - 100 W is connected to a 160 V power supply. The power consumed by it would be:

• A. 64 W
• B. 80 W
• C. 100 W
• D. 125 W

Answer 1

Answer: (A)

64 W

Answer 2

The power consumed by a device is related to the voltage applied and the resistance of the device.
The formula for power is:
$P=\frac{V^2}{R}$​.
The resistance R of the bulb can be found using the rated voltage and power of the bulb, which are 200 V and 100 W, respectively.
We use the formula
$R = \frac{V_{\text{rated}}^2}{P_{\text{rated}}} = \frac{200^2}{100} = 400 \, \Omega$
Now, we calculate the power consumed when the voltage applied is 160 V using the same formula:
$P = \frac{160^2}{400} = \frac{25600}{400} = 64 \, W$
Thus, the power consumed by the bulb when connected to a 160 V power supply is 64 W.