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

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

Accepted Answer

The resistance of the bulb can be found using the formula $R = \frac{V^2}{P} = \frac{220 	imes 220}{100} = 484 \,\Omega$. When the bulb is operated on $V' = 110	ext{ V}$, the power consumed is $P' = \frac{(V')^2}{R} = \frac{110 	imes 110}{484} = \frac{12100}{484} = 25	ext{ W}$.

Electricity

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