Two equal magnitude point charges are a distance: a apart along the z axis. (a) When the charge are of the same polarity, the electric field due: to each is radially directed away. In the z= 0 symmetry plant:. the net field component is radial.
(b) When the charges are of opposite polarity, the electric field due 10 the negative charge is directed radially inwards. In the z = 0 symmetry plane. the net field is now -z directed.