Question

Two charges q₁ and q₂ are placed at (0, 0, d) and (0, 0, –d) respectively. Find locus of points where the potential a zero.

Answer 1

Thus, to have total potential zero, q₁ and q₂ must have opposite signs. Squaring and simplifying, we get.

This is the equation of a sphere with centre at

Note : if q₁ = –q₂ =>Then z = 0, which is a plane through mid-point.

Answer 2

Key concept: Following the principle of superposition of potentials as
described in last section, let us find the potential V due to a collection of
discrete point charges q₁, q₂, …,q_n, at a point P.