Question

The angle between electric lines of force and equipotential surface is
(A) $0^\circ $
(B) $180^\circ $
(C) $90^\circ $
(D) $45^\circ $

Answer 1

Hint Electrical lines of force can be described as a path of an electric field at that point. It can be either straight or curved so that the tangent gives the direction of the intensity of the electric field at that point of the electric field. We apply the conditions for an equipotential surface on electric lines of force and find the angle between the two.

Complete step by step answer Equipotential surface is the surface on which the potential is equal throughout the surface. Let us consider an electric line of forces going from left to right parallel to each other.
As we move from left to right on electric lines of force the potential decreases or increases. The increase or decrease in potential while moving from left to right on any electric line of force is the same for all the electric lines of force. This tells us that at a particular point on all the electric lines of forces the potential is equal. When we connect all these points it makes a straight line perpendicular to the electric lines of force.
Hence the angle between electric lines of force and equipotential surface is $90^\circ $

Option (C) $90^\circ $ is the correct answer

Note In this case, if a single point charge we assume that the second charge is at an infinite distance similarly solves the question. Even in this case, the angle is $90^\circ $. Electric lines of force are formed due to two-point charges or two planes of charges. These two charges should be the same if the force should be repulsive and if the force should be attractive then the charges should be the opposite.