1. The problem statement, all variables and given/known data A long wire (X) carrying a current of 30 A is placed parallel to, and 3.0 cm away from, a similar wire (Y) carrying a current of 6.0 A. What is the flux density midway between the wires: (a) when the currents are in the same direction, (b) when they are in opposite directions? (c) When the currents are in the same direction there is a point somewhere between X and Y at which the flux density is zero. How far from X is this point? (μ0 = 4 π * 10 -7 H m-1.) Answers: (a) 3.2 * 10-4 T, (b) 4.8 * 10-4 T, (c) 2.5 cm 2. The attempt at a solution (a) B = μ0 I / 2 π a = [4 π * 10 -7 * (30 - 6)] / 2 π * (0.03 / 2) = 3.2 * 10-4 T. I is (30 - 6) since the currents are in the same direction and 0.03 is divided by two because we need the flux density midway between the wires. (b) Same formula but 30 + 6, since the currents are in opposite directions = 4.8 * 10-4 T. (c) Regarding this part I don't know. I used the abovementioned formula and got: [4 π * 10 -7 * (30 - 6)] / 2 π * a = 0 → 7.2 * 10-6 a-1 = 0. And that's as far as I got.