Question

A positive charge $q$ is placed in front of a conducting solid cube at a distance $d$ from its centre. Find the electric field at the centre of the cube due to the charges appearing on its surface.

Answer 1

Since field inside a conductor is always $0$.

Hence field due to charge $q$ and those appearing at surface should cancel each other.

Hence, the magnitude of field at center due to charges appearing at surfaces is

$E=\frac{q}{4\pi {ϵ}_o{d}^2}$