Physics - Current Electricity Question with Solution | TestHub

Let resistance of a wire $R$ and length 1 .
$\mathrm{R}=\frac{\rho \ell }{\mathrm{A}}=5\Omega$
$\therefore$ Volume of wire is constant in stretching
$V_i=V_f\Rightarrow A_i{\ell }_i=A_f{\ell }_f$
$\mathrm{A}\ell ={\mathrm{A}}^{\prime }(5\ell )\Rightarrow {\mathrm{A}}^{\prime }=\frac{\mathrm{A}}{5}$
$R_f=\frac{\rho {\ell }_f}{A_f}=\frac{\rho (5\ell )}{\left(\frac{A}{5}\right)}=25\left(\frac{\rho \ell }{A}\right)=25\times 5=125\Omega$