Parts of a Motor

By Graham Beckett; Updated April 24, 2017
Part of an electric motor.

People often use the word "motor" to describe the engine in their car, but the term usually refers to electric motors. The development of these devices revolutionized society and helped pulled the world into the modern technological era. Electric motors come in all sizes and configurations, but they all function on the same principle with the same fundamental parts.

Basic Principles

Motors work through electromagnetism. If you run electricity through a wire, it creates a magnetic field. If you coil the wire around a rod and run electricity through the wire, it creates a magnetic field around the rod. When you surround that rod with other magnets, the rod will rotate as the magnets attract and repel each other.

The Stator

Every electric motor has two essential parts: one stationary, and one that rotates. The stationary part is the stator. Though configurations vary, the stator is most often a permanent magnet or row of magnets lining the edge of the motor casing, which is usually a round plastic drum.

The Rotor

Inserted into the stator is the rotor, usually consisting of copper wire coiled around an axle. When current is applied to the coil, the resulting magnetic field interacts with that created by the stator, and the axle begins to spin.

The Commutator

An electric motor has another important component, the commutator, which sits at one end of the coil. It is a metal ring divided into two halves. It reverses the electrical current in the coil each time the coil rotates half a turn. The commutator periodically reverses the current between the rotor and the external circuit, or the battery. This ensures that the ends of coils do not move in opposite directions, and ensures that the axle spins in one direction.

Brushes and Terminals

At one end of the motor are the brushes and the terminals. They are at the opposite end from where the rotor exits the motor casing. The brushes send electrical current to the commutator and are typically made of graphite. The terminals are the locations where the battery attaches to the motor and sends the current to spin the rotor.

About the Author

Graham Beckett is an attorney in Los Angeles who has practiced in California since 2006, providing thoughtful analysis and writing on various legal issues. Additionally, he is an avid surfer, runner, and comedy writer, writing and performing in various sketch shows throughout Los Angeles.