A 1.59 m long wire weighing 0.0668 N/m is suspended directly above an infinitely straight wire. The top wire carries a current of 32.4 A and the bottom wire carries a current of 24.5 A. Find the distance of seperation between the wire so that the top wire will be held in place by the magnetic repulsion. Ok. So the formula that I wanted to use was F/l = (u x I1 x I2) / (2 x pi x a) where F/l is 0.0668 N/m l = 1.59 m u = 4 x pi e - 7 T.m/A I1 = 32.4 A I2 = 24.5 A a = ? But this is not a parallel wire question, it's a perpendicular wire question. If I use the formula B = (u x I) / (2 x pi x r) where r is the perpendicular distance to the wire, then will I have to ignore the current of the bottom wire? and I don't have the B. I'm confused. Can anyone help? Thanks guys.