If current in an electric bulb changes by $1\%$, then the power will change by ............ $\%$
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$P = {i^2}R$ $ \Rightarrow $ $\frac{{\Delta P}}{P} = \frac{{2\Delta i}}{t}$ ($R$ $\to$ Constant)
$ \Rightarrow $ $\%$ change in power $ = 2 \times $ $\%$ change in current
$=2 \times 1 = 2\% $
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