A copper wire is stretched to make it 0.1 % longer. The percentage change in its resistance is
Answer & explanation
Correct answer: option 1
$ R = \frac{\rho l}{A} $
$ l.A = V = constant$
$ \Rightarrow R = \frac{\rho l^2}{V} $
$ \frac{\Delta R}{R} = 2\frac{\Delta l}{l} = 0.2 \%$ Increase