An infinitely long current carrying wire and a small current carrying loop are in the plane of the paper as shown. The radius of the loop is a and distance of its centre from the wire is d (d>>a). If the loop applies a force F on the wire then :
(1) $F\propto\left({a^2\over d^3}\right)$
(2) $F\propto\left({a\over d}\right)$
(3) $F\propto\left({a\over d}\right)^2$
(4) $F = 0$