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(C) The resistance $R$ of a wire is given by $R = ho \frac{L}{A}$.Since the volume $V = A 	imes L$ remains constant when the wire is stretched,we h

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$44$

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(C) The resistance $R$ of a wire is given by $R = ho \frac{L}{A}$.Since the volume $V = A 	imes L$ remains constant when the wire is stretched,we have $A = \frac{V}{L}$.Substituting this into the resistance formula,we get $R = ho \frac{L^2}{V}$.Since $ho$ and $V$ are constants,$R \propto L^2$.If the length increases by $20 \%$,the new length $L' = L + 0.20L = 1.2L$.The new resistance $R' \propto (1.2L)^2 = 1.44L^2$.Therefore,$R' = 1.44R$.The percentage increase in resistance is $\frac{R' - R}{R} 	imes 100 = \frac{1.44R - R}{R} 	imes 100 = 0.44 	imes 100 = 44 \%$.

If a copper wire is stretched to increase its length by $20 \% $,the percentage increase in resistance of the wire is $..........\%$.

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