A straight segment OC (of length L meter) a circuit carrying a current I amp is placed along the x-axis. Two infinitely long straight wires A and B, each extending from z = ∞ to -∞ , are fixed at y = -a metre and y = +a metre respectively, as shown in figure. If the wires A and B each carry a current I amp into plane of the paper. Obtain the expression for the force acting on the segment OC. What will be the force on OC if the current in the wire B is reversed ?