Question

Four point charges `-Q, -q, 2q` and `2Q` are placed, one at each corner of the square. The relation between `Q` and `q` for which the potential at the centre of the square is zero is
A. `Q = -q`
B. `Q = -(1)/(q)`
C. `Q = q`
D. `Q = (1)/(q)`

Answer 1

Correct Answer - 1

`V_(o) = (1)/( 4pi epsilon_(0)) [ (-Q)/(r ) + (-q)/(r ) + (2q)/(r ) + (2Q)/(2)] = 0`
`Q + q = 0`
`Q = -q`