An electric bulb marked $40\, W$ and $200\, V$, is used in a circuit of supply voltage $100\, V$. Now its power is
AIIMS 2002, Medium
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(d) $P = \frac{{{V^2}}}{R}$ $ \Rightarrow \frac{{{P_2}}}{{{P_1}}} = \frac{{V_2^2}}{{V_1^2}}$ ( is constant)
$ \Rightarrow \frac{{{P_2}}}{{{P_1}}} = {\left( {\frac{{100}}{{200}}} \right)^2} = \frac{1}{4}$$ \Rightarrow {P_2} = \frac{{{P_1}}}{4} = \frac{{40}}{4} = 10\,W$
$ \Rightarrow \frac{{{P_2}}}{{{P_1}}} = {\left( {\frac{{100}}{{200}}} \right)^2} = \frac{1}{4}$$ \Rightarrow {P_2} = \frac{{{P_1}}}{4} = \frac{{40}}{4} = 10\,W$
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