All points on an equipotential surface have the same electric potential (i.e. the same voltage). The electric force neither helps nor hinders motion of an electric charge along an equipotential surface. Electric field lines are always perpendicular to an equipotential surface.

What do you mean by Equipotentia surface?

What is Equipotential Surface? The surface which is the locus of all points which are at the same potential is known as the equipotential surface. No work is required to move a charge from one point to another on the equipotential surface.

Is electric field always zero on equipotential surface?

An equipotential surface is everywhere perpendicular to the electric field that it characterizes. The work done by the electric field on a particle when it is moved from one point on an equipotential surface to another point on the same equipotential surface is always zero.