1. The problem statement, all variables and given/known data In the figure, the top wire is 1.1 mm-diameter copper wire and is suspended in air due to the two magnetic forces from the bottom two wires. The current is 45 A in each of the two bottom wires. Calculate the required current flow in the suspended wire. http://i37.tinypic.com/2u3v8sm.jpg 2. Relevant equations F = mg F(of wire1 on wire2) = I1 * I2 * u0 * length of wire2 / 2*pi*r (second equation derived from equation from B, u0 * I / 2pi r) 3. The attempt at a solution I've drawn a FBD with two forces going up (sin(60)* force from each of the two lower wires), and one force going down (that of gravity). I've set the two up equal to the one down. (Force down = mg, and I calculated mg by using r^2 pi * length * density of copper (8.92 g/ cm^2) ). This allows the "length" factor to cancel out, since we're not told what it is. Then I solved for the second current (since the first one is given as 45) ... unfortunately I'm not getting the right answer. Any tips? Thank you!