Three charges +Q, q, +Q are placed respectively, at distance, 0, d//2 and d from the origin, on the x-axis. If the net force experienced by +Q placed at x=0, is zero, then value of q is :

Options

A. `-Q/2`
B. `-Q/4`
C. `+Q/2`
D. `+Q/4`

Answer

B

Explanation

IF net force on +Q (at x=0) is zero, then
Magnitude of force of q an Q( at x=0) =Magnitude of force by
`Q (at x=d) an Q(at x=0) and the directions are exactly opposite so q is -ve.
`implies (KQq)/(d//2)^2 =(dQ2)/d^2 implies q=-Q/4` i.e., option (B)