ETYM See the nouns Bank and the verbs derived from them.
1. Someone who owns or is an executive in a bank.
2. The person in charge of the bank in a gambling game.
For reversing the direction of an electric current.
Electricity, device transforming alternating current produced by dynamo into direct current, especially segmented drum bearing brushes which collect the current.
Device in a DC (direct-current) electric motor that reverses the current flowing in the armature coils as the armature rotates.
A DC generator, or dynamo, uses a commutator to convert the AC (alternating current) generated in the armature coils into DC. A commutator consists of opposite pairs of conductors insulated from one another, and contact to an external circuit is provided by carbon or metal brushes.