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.

Ans (a).

Equidistant planes parallel to the x-y plane are the equipotential surfaces.

Ans (b).

Planes parallel to the x-y plane are the equipotential surfaces with the exception that when the planes get closer, the field increases.

Ans (c).

Concentric spheres centered at the origin are equipotential surfaces.

Ans (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.