Current Loop Torque in Electric Motors

Current loop torque in electric motors shows how magnetic force can make a wire loop rotate. In an electric motor, loops of wire sit between magnets in a magnetic field. When current flows through the loops, the field applies torque. This rotation turns a shaft and converts electrical energy into mechanical energy.

Consider a rectangular current-carrying loop of lengths a and b placed in a uniform magnetic field, with an axis of rotation passing through point O at distance m from one end.

The magnetic forces acting along the plane of the loop lie on the same axis passing through O; thus, the sum of their torques about the axis is equal to zero.