Two thin wire rings each having a radius R are placed at a distance d apart with their axes coiciding. The charges on the two rings are `+q` and `-q`. The potential difference between the centres of the two rings is

Options

A. `(qR)/(4pi epsilon_(0) d^(2))`
B. `(q)/(2pi epsilon_(0))[(1)/(R ) - (1)/(sqrt(R^(2) + d^(2)))]`
C. zero
D. `(q)/(4pi epsilon_(0))[(1)/(R ) - (1)/(sqrt(R^(2) + d^(2)))]`

Answer

B