Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

A surface on which the potential at every point is equal is called an equipotential surface. The value of potential difference between any two points on an equipotential surface is zero. Therefore, the work done in bringing a charge from one point to another point on an equipotential surface is equal to zero. But the work done is zero only when the charge is moved in a direction perpendicular to the electric field. Therefore, the equipotential surface is perpendicular to the electric field at every point.