A closed-loop PQRS carrying a current is placed in a uniform magnetic field. If the magnetic forces on segments PS, SR, and RQ are F1, F2, and F3 respectively, and are in the plane of the paper and along the directions shown, the force on the segment QP is
None
According to the figure the magnitude of the force on the segment QM is and PM is
.
Therefore, the magnitude of the force on segment PQ is