Question

Through which of the spheres, net electric flux is zero?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

We know that electric flux through any surface is defined as number of field lines passing perpendicular to it.
If same number of field lines enter and leaves a given surface, then net electric flux through the surface is zero.
For example,


Field lines are perpendicular to faces $\text{ABCD}$ and $\text{EFGH}$. At all other four faces field lines are tangential. So, net flux passing through these four faces will be zero.

Here, only in option $\left(c\right)$, the number of field lines entering and leaving the surface is same, thus, net electric flux is zero.