Question

Two point charges of 9e and e are placed at a distance of 'r'. At what distance another charge q be kept away from 9e charges on the line joining the charges so that the system remains in equilibrium-

• A. r/4
• B. r/2
• C. 3r/4
• D. r/3

Answer 1

Answer: (C)

3r/4

Answer 2

No calculation is required, equilibrium point should be closer to e, so answer is $\frac { 3 r } { 4 }$ .