Question

if the change in resistance of copper wire on stretching is 4%, then its length is stretched by

Answer 1

Explanations & Calculations

$\qquad\qquad \begin{aligned} \small R_1&=\small \rho.\frac{L_1}{A_1}\qquad\qquad R_2= \rho.\frac{L_2}{A_2}\\ \small R_2&=\small 1.04R_1\\ \small \frac{L_2}{L_1}&=\small 1.04.\frac{A_2}{A_1}\cdots(1)\\ \\ \small Vol=A_1L_1&=\small A_2L_2\\ \small \frac{A_2}{A_1}&=\small \frac{L_1}{L_2}\cdots(2)\\ \\ \small \frac{L_2}{L_1}&=\small \sqrt{1.04}\\ &=\small 1.02\\ \small \frac{L_2-L_1}{L_1}\times100\%&=\small 2\% \end{aligned}$