Question

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be:

• A. 100 W
• B. 75 W
• C. 50 W
• D. 25 W

Answer 1

The correct option is D

25 W

Let's find the resistance value of the bulb when it is operated under the rated conditions.

P = $\frac{V^2}{R}$

R = $\frac{V^2}{P}$ = $\frac{{220}^2}{100}$

Now, when the bulb is operated across 110 V then Power = $\frac{{110}^2}{R}$

Hence, P = 25 W