Physics - Current Electricity Question with Solution | TestHub

Key Idea : In stretching, specific resistance remains unchanged. After stretching, specific resistance $(\rho )$ will remain same. Original resistance of the wire, $R=\frac{\rho l}{A}$ $R\propto \frac{l}{A}\text{ or }R\propto \frac{l^2}{V}$ (as $V=Al$) and $R^{\prime }\propto \frac{(l+10\%l{)}^2}{V}$ Therefore, $\frac{R^{\prime }}{R}=\frac{{\left(l+\frac{10}{100}l\right)}^2}{l^2}$ $\frac{R^{\prime }}{R}=\frac{{\left(\frac{11l}{10}\right)}^2}{l^2}=\frac{121}{100}$ $R^{\prime }=1.21R$