No work is done in moving a test charge over an equipotential surface, why?

No work is done in moving a test charge over an equipotential surface. Explain, why.

Work done in moving a positive charge on an equipotential surface is

Work done in moving a positive charge on an equipotential surafce is

The work done in moving a positive charge on an equipotential surface is:

Assertion(A): A point charge q is rotated along a circle around another point charge Q .The work done by electric field on the field on the rotating charge in half revolution is zero. Reason (R ) :No work is done to move a charge on an equipotential line or surface.

How much work is done when a charge q moves over an equipotential surface?