Physics – 4.5.5 The d.c. motor | e-Consult

A split-ring commutator is a critical component in a DC electric motor, responsible for reversing the direction of the current in the armature coils at regular intervals. This ensures that the force on the armature conductors maintains a consistent direction, leading to continuous rotation.

Diagram: (A diagram would be included here, but cannot be rendered in plain HTML. The diagram should show a circular armature with coils, a split ring commutator attached to the armature, and two brushes making contact with the commutator. The magnetic field should be indicated around the armature.)

The commutator consists of two half-rings, separated by a small air gap. These rings are connected to the armature coils. Brushes are made of carbon and are spring-loaded to maintain constant contact with the commutator. As the armature rotates, the brushes make contact with one half-ring, allowing current to flow in one direction. As the armature continues to rotate, the brushes switch to the other half-ring, reversing the direction of the current.

The purpose of the commutator is to ensure that the force on the armature conductors is always in the same direction. If the current were not reversed, the force would reverse direction when the armature reached a certain position, causing the motor to stop. The commutator prevents this by continuously reversing the current, maintaining a consistent force and thus continuous rotation.