The equipotential surfaces corresponding to a single positive charge are concentric spherical shells with the charge at its origin. The spacing between the surfaces for the same change in potential:
Describe schematically the equipotential surfaces corresponding to
(a) a constant electric field in the z-direction,
(b) a field that uniformly increases in magnitude but remains in a constant (say, z) direction,
(c) a single positive charge at the origin, and
(d) a uniform grid consisting of long equally spaced parallel charged wires in a plane.