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) Equipotential surface of constant electric field in z-axis is parallel to xy-plane which is shown in figure.

(b) Here also planes parallel to the xy-plane are equipotential surfaces in z-direction with the exception that when the plane gets closer the field increases.
( c ) If a single positive charge placed on a origin then concentric spheres are equipotential surfaces. Distance between two successive surfaces are same and electric potential constantly decreases from the centre.

(d) Near the grid, the equipotential surfaces will have varying shape. At far off distances from the grid, the equipotential surfaces will be planes parallel to the grid.