If a wire is stretched to make it 0.1 % longe | vedclass

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

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increase by $0.2 \%$

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(B) The resistance of a wire is given by $R = \frac{ho l}{A}$.Since the volume $V = A 	imes l$ remains constant when the wire is stretched,we can write $A = \frac{V}{l}$.Substituting this into the resistance formula,we get $R = \frac{ho l^2}{V}$.Since $ho$ and $V$ are constants,$R \propto l^2$.Taking the derivative or using the approximation for small changes,the fractional change in resistance is given by $\frac{\Delta R}{R} = 2 \frac{\Delta l}{l}$.Given that the wire is stretched by $0.1 \%$,we have $\frac{\Delta l}{l} = 0.1 \% = 0.001$.Therefore,$\frac{\Delta R}{R} = 2 	imes 0.1 \% = 0.2 \%$.Since the change is positive,the resistance will increase by $0.2 \%$.

If a wire is stretched to make it $0.1 \%$ longer,its resistance will

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