Question

$1$C of charge is placed at the centre of cube of side $5$cm the electric flux coming out from any face of the cube is?

• A. Zero
• B. $1/2{\epsilon }_0$
• C. $\frac{1}{6{\epsilon }_0}$
• D. $\frac{1}{3{\epsilon }_0}$

Answer 1

The correct option is D $\frac{1}{3{\epsilon }_0}$

Net flux coming out from all sides of the cube is
$\varphi =\frac{1}{{\epsilon }_0}\sum q=\frac{2}{{\epsilon }_0}$
As the cube has six faces, so the flux through each face will be
${\varphi }^{\prime }=\frac{\varphi }{6}=\frac{\frac{2}{{\epsilon }_0}}{6}$
$=\frac{2}{{\epsilon }_0}\times \frac{1}{6}=\frac{1}{3{\epsilon }_0}$.