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

By defination, an equipotential surface is that at every point of which potential is the same. In the four cases given above :
(a) Equipotential surfaces are planes parallel to X-Y plane. These are equidistant.
(b) Eequipotential surfaces are planes parallel to X-Y plane. As the field increases uniformly, distance between the planes (differeng by fixed potential) decreases.
(c) Equipotentail surfaces are concetric spheres with origin at the center.
(d) Equipotential surfaces have the surfaces have the shape which changes periodically. At far off distances from the grid, the shape of equipotenial surfaces becomes parallel to the grid itself.