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

Options

A. Q=q
B. `Q=(1)/(q)`
C. Q=-q
D. `Q=-(1)/(q)`

Answer

C

Explanation

Potential V at centre of the square `=(-kQ)/(r )-(kq)/(r )+(k2Q)/(r )+(k2q)/(r )=0`
So Q=- q