Question

What is the flux through a cube of side $a$ if a point charge of $q$ is at one of its corner?

• A. $\frac{2q}{{\epsilon }_0}$
• B. $\frac{q}{8{\epsilon }_0}$
• C. $\frac{q}{{\epsilon }_0}$
• D. $\frac{3q{a}^2}{{\epsilon }_0}$

Answer 1

The correct option is B $\frac{q}{8{\epsilon }_0}$



Eight identical cubes are required so that the given charge $q$ appears at the centre of the bigger cube.

Thus the electric flux passing through the given cube is,

$\varphi =\frac{1}{8}\left(\frac{q}{{\epsilon }_0}\right)=\frac{q}{8{\epsilon }_0}$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, (b) is the correct answer.