Give an example of a line in the electric field of an electric dipole along which a positive charge may be moved without any work being done.

Explanation

There are numerous equipotential surface in the electric field of a dipole. Any movement of a charge, on any of these surfaces, would involve no work. For example, the plane perpendicular to the dipole and passing through its mid-point is an equipotential, actually a zero-potential surface. So if a positive charge be moved along any line on this plane, no work is to be done.