Question

Two horizontal parallel wires which carry currents I1 = 45 A (top)and I2 (bottom). The top wire is held in position, the bottom wire is prevented from moving sideways but can slide up and down without friction. If the wires have a mass of 9.2 g per metre of length, calculate current I2 such that the lower wire levitates at a position 5.6 cm below the top wire.