Electric Charges And Fields

There is no potential gradient along any direction parallel to the surface. Any surface over which the electric potential is same everywhere is called an equipotential surface. The electric field and hence, lines of force everywhere are at right angles to the equipotential surface. This is so, because there is no potential gradient along any direction parallel to the surface and, so no electric field parallel to the surface. This means the electric field and hence, lines of force are always at right angles to the equipotential surface. Hence, they are not concentric spheres for uniform electric field. They are concentric spheres for an isolated point charge. Rest option (a), (c), (d) are properties of equipotential surface.

According to Gauss theorem, "the net electric flux through any closed surface is equal to the net charge inside the surface divided by '' . Therefore, Let - be the charge, due to which flux is entering the surface or Let be the charge, due to which flux is leaving the surface or So, electric charge inside the surface = =