← Back to Test

Problem 2 - Olympiad

Two infinite parallel wires separated by a distance 2d carry currents I in opposite directions. A square loop of side d is placed between them, centered at a distance d from each wire. What is the net torque on the loop in the magnetic field produced by the two wires?

Correct: A

The magnetic field from each wire at the position of the square loop cancels due to symmetry. The top and bottom arms of the loop experience equal and opposite forces, while the left and right arms also cancel each other's forces since the loop is equidistant from both wires. Hence, all forces cancel, resulting in zero net torque on the loop.