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

An electric motor operates based on the principle of electromagnetic force. When a current-carrying conductor is placed within a magnetic field, it experiences a force. This force is described by Fleming's Left-Hand Rule. The magnetic field is typically created by permanent magnets or electromagnets. The current-carrying conductors are usually coils of wire, often arranged in a series of loops called armature coils.

The current flowing through the armature coils creates a magnetic field around the coils. This magnetic field interacts with the external magnetic field, resulting in a force on the current-carrying conductors. This force causes the armature to rotate. The direction of the force is perpendicular to both the direction of the current and the direction of the magnetic field.

A split-ring commutator is crucial for maintaining continuous rotation. As the armature rotates, the brushes make contact with the split rings. These rings are connected to the armature coils. As the armature rotates, the brushes switch the direction of the current flowing through the coils at regular intervals (typically 180 degrees). This reversal of current ensures that the force on the conductors maintains a consistent direction, causing the armature to continue rotating in the same direction. Without the commutator, the armature would simply rotate to the point where the magnetic field alignment is reversed, and then stop.