Question

Calculate the resistance of $1km$ long copper wire of area of cross section $2\times {10}^{-2}{cm}^2$. The resistivity of the copper wire is $1.62\times {10}^{-8}ohm-metre$.

Answer 1

We know that resistance $R=\frac{\rho \times l}{A}$, here, $l=1km=1000m,A=0.02c{m}^2,\rho =1.62\times {10}^{-8}\Omega -m$

$=\frac{1.62\times {10}^{-8}\times 1000}{2\times {10}^{-2}\times {10}^{-4}}$

$=8.1\Omega$

so resistance will be $8.1\Omega$