Definition
A segmented copper ring mounted on the armature shaft of a DC motor or generator. As the armature rotates, the commutator segments make sliding contact with stationary brushes, reversing the connection to the external circuit at the correct moment so that the output current flows in one consistent direction.
Plain English
A rotating switch built into a DC motor or generator. It flips the electrical connection at just the right point in each turn so the current always comes out flowing the same way.
Context Anchor
Seen in aircraft electrical-system maintenance, especially with DC starters, generators, and starter-generators.
Derivation
From the Latin commutare, meaning 'to change' or 'to exchange.' The name fits because the device's job is to keep changing (switching) the electrical connection as the shaft turns.
Why Pilots Care
A worn or damaged commutator prevents starter motors and other DC equipment from operating reliably, which can ground an aircraft or cause in-flight electrical failures.
Analogy
Think of it as a rotating switch. Instead of a person flipping the switch by hand, the turning part flips the electrical connections automatically over and over.
Intuition Check
A commutator does not create electricity by itself. Its job is to switch connections between the spinning coils and the outside circuit at the right moments.
Example Sentence 1
The mechanic found the generator was producing low output because the commutator was pitted and the brushes were no longer making clean contact.
Example Sentence 2
During the preflight, the pilot noted that the generator commutator needed cleaning to restore proper charging.