Electric vehicles use a direct current (d.c.) electric motor powered by a battery for propulsion - Edexcel - A-Level Physics - Question 16 - 2023 - Paper 1

Current Direction: In the coil, the current flows from D to C in one segment and from A to B in the other segment. This current direction influences the forces acting on the coil.

Magnetic Forces: The arrangement creates a magnetic field due to the presence of the magnet (N-S). The magnetic force on side DC of the coil produces an upward force, while the force on side AB acts downward. According to the right-hand rule, the direction of the force can be determined by the orientation of the magnetic field and current.

Resultant Torque: The unequal forces on the two sides of the coil create a torque, which causes the coil to rotate about its axis. This torque continues to exert a rotational effect, leading to continuous motion.

Split Ring Function: The split ring (commutator) ensures that the current direction in the coil is reversed each half-turn, maintaining the rotational direction of the coil. The action of the brushes facilitates this current switching by maintaining contact with the split ring, allowing for consistent torque on the coil.

Continuity of Motion: The resultant motion is sustained as long as the current flows and the external magnetic field is present, allowing the electric motor to perform its function efficiently.