Q. Four point charges −Q, −q, 2q and 2Q are placed, one at each corner of a square. The relation between Q and q for which the potential at the centre of the square is zero is
A) Q = 1/q
B) Q = −q
C) Q = −1/q
D) Q = q
Explanation
[Solution from source] All four charges are at the same distance from the centre, so the potential is proportional to the sum of charges: −Q − q + 2q + 2Q = Q + q. For zero potential, Q = −q. Q = q would make the sum 2q, not zero. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.