Question

Two idential point charges 'Q' are kept
at a dielance 'r' from each other. A
third point charge is placed in the line
joining the above two changes such that
all the 3 changes are in equilibrium. What is the magnitude,
sign and position of the
3rd charge ?​

Answer 1

Explanation:

For charge -q to be in equilibrium, the force acting on '-q' due to +Q at A and +Q at B should be equal and opposite. i.e., the position of the third charge is at x=r/2.