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.

Explanation

(a) Equidistance planes parallel to the x-y plane are the equipotential surfaces
(b) planes parallel to the x-y plane are the equipotential surfaces with the exception that when the planes get closer , the field incraeses.
(c) concentric spheres centred at the origin are equipotential surface
(d) a periodically varying shape near the given grid is the equipotential surface. this shape gradually reaches the shape of planes parallel to the grid at a larger distance.