posted by Anne .
The drawing shows four insulated wires overlapping one another, forming a square with 0.050-m sides. All four wires are much longer than the sides of the square. The net magnetic field at the center of the square is 91.5 µT. Calculate the current I.
It matters how the current is flowing in each of the wires.
If the currents are flowing in the same direction, they repel one another and you take the difference of I for wires in parallel with each other. If they flow in the same direction you take the sum of I. Do that for both sides of parallel lines and add your equations then set the equation equal to the net magnetic field in the center.