Which of the following statements are true? Check all that apply. Check all that apply. When all charges are at rest, the surface of a conductor is always an equipotential surface. Electric field lines and equipotential surfaces are always mutually perpendicular. The potential energy of a test charge increases as it moves along an equipotential surface. An equipotential surface is a three-dimensional surface on which the electric potential is the same at every point. The potential energy of a test charge decreases as it moves along an equipotential surface.