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If a wire is stretched to make it $0.1 \%$ longer, its resistance will :
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Verified Answer
The correct answer is:
increase by $0.2 \%$
increase by $0.2 \%$
$\mathrm{R} \propto \ell^2$ (for a given volume)
$$
\Rightarrow \frac{\Delta \mathrm{R}}{\mathrm{R}} \%=\frac{2 \Delta \ell}{\ell} \%
$$
Thus when wire is stretched by $0.1 \%$ resistance increases by $0.2 \%$
$$
\Rightarrow \frac{\Delta \mathrm{R}}{\mathrm{R}} \%=\frac{2 \Delta \ell}{\ell} \%
$$
Thus when wire is stretched by $0.1 \%$ resistance increases by $0.2 \%$
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