Question

A point charge $4\mu C$ is at the centre of a cubical Gaussian surface of 10 cm edge. Net electric flux through the surface is:

• A. $2.5\times {10}^{5}N{m}^2{C}^{-1}$
• B. $4.5\times {10}^{5}N{m}^2{C}^{-1}$
• C. $4.5\times {10}^{6}N{m}^2{C}^{-1}$
• D. $2.5\times {10}^{6}N{m}^2{C}^{-1}$

Answer 1

The correct option is B $4.5\times {10}^{5}N{m}^2{C}^{-1}$

Here, $q=4\mu C=4\times {10}^{-6}C,l=10cm=10\times {10}^{-2}m$
$\varphi =\frac{q}{{ϵ}_0}=\frac{4\times {10}^{-6}}{8.85\times {10}^{-12}}=4.5\times {10}^{5}N{m}^2{C}^{-1}$