Four charges, each equal to –Q, are placed at the corners of a square and a charge +q is
placed at its centre. If the system is in equilibrium, the value of q is .........
Options:
(a) `Q/4(1+2sqrt2)`
(b) `-Q/4(1+2sqrt2)`
(c) `-Q/2(1+2sqrt2)`
(d) `Q/2(1+2sqrt2)`