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

As the constant electric field in the Z-axis direction, the equipotential surfaces are normal to the field, i.e., in xy-plane. The equipotential surfaces are equidistant from each other.