Q. 3.     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

Answers (1)

Given : V=220V,P=100W

        P=\frac{V^2}{R}

The resistance of the bulb

\Rightarrow R=\frac{V^2}{P}=\frac{(220)^2}{100}=484\Omega

If bulb is operated on 110 Vand resistance is the same , the power consumed will be P'

P'=\frac{V^2}{R}=\frac{(110)^2}{484}=25W

Hence, option D is correct.

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