JEE MAIN - Physics (2006 - No. 36)
An electric bulb is rated $$220$$ volt - $$100$$ watt. The power consumed by it when operated on $$110$$ volt will be
$$75$$ watt
$$40$$ watt
$$25$$ Watt
$$50$$ Watt
Explanation
The resistance of the bulb is $$R = {{{V^2}} \over P} = {{{{\left( {220} \right)}^2}} \over {100}}$$
The power consumed when operated at $$110$$ $$V$$ is
$$P = {{{{\left( {110} \right)}^2}} \over {{{\left( {220} \right)}^2}/100}} = {{100} \over 4} = 25\,W$$
The power consumed when operated at $$110$$ $$V$$ is
$$P = {{{{\left( {110} \right)}^2}} \over {{{\left( {220} \right)}^2}/100}} = {{100} \over 4} = 25\,W$$
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