Question

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

• `(+Q)/2`

• `(-Q)/4`

• `(-Q)/2`

• `(+Q)/4`

Answer 1

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 `(-Q)/4`.

Explanation:

F_origin = `Q^2/(4piepsilon_0d^2) +  (Q_q xx 4)/(4piepsilon_0d^2)` = 0

`therefore (Q_q xx 4)/(4piepsilon_0d^2) - Q^2/(4piepsilon_0d^2)`

`therefore q = - Q/4`