If a copper wire is stretched to increase its length by $20 \% $. The percentage increase in resistance of the wire is $..........\%$
JEE MAIN 2023, Medium
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As volume is constant,
So resistance $\propto$ (length $)^2$
$\Rightarrow \% \text { change in resistance }=20+20+\frac{400}{100}=44 \%$
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