When two infinitely long parallel wires separated by a distance of 1m, each carry a current of 3 ampere, the force in newton/ metre length experienced by each will be, (given ${\mathrm{\mu }}_0=4\mathrm{\pi }\times {10}^{-7}$ S.I. Units).

An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current $I$ along the same direction is shown in Figure. Magnitude of force per unit length on the middle wire $B$ is given by

Loop $ABCD$ and long straight wire are in the same plane. Side $CD=2AB$. Distance between long straight wire and $AB$ is equal to the distance between $AB$ and $CD$. Net force on the loop is