JEE Main 2018 — Electrostatics Question with Solution

As in a cube there is 6 faces, you can think this surface is one face among 6 faces. If the side of cube is a length then its center will be $$\frac{a}{2}$$ distance from any surface.

So, we can assume point charge Q is at the center of the cube and total electric flux due to this charge will pass evently through the six faces of the cube.

So, electric flux through one face will be $$\frac{1}{6}$$. of the total electric flux.

Flux through 6 faces of the cube $$=\frac{Q}{{\epsilon }_0}$$

$$\therefore$$ Flux through 1 face of the cube = $$\frac{Q}{6{\epsilon }_0}$$