short for dynamoelectric machine. A machine for converting energy in the form of mechanical power into energy in the form of electric currents, by the operation of setting conductors (usually in the form of coils of copper wire) to rotate in a magnetic field.
The full name dynamo-electric machine was given by Siemens in 1867, to distinguish his invention from the magneto-electric machines previously used, in which the electric current was generated by means of a permanent magnet. But in the shortened form dynamo (recommended by Prof. S. P. Thompson early in 1882), the use of the word has been extended so as to include all forms of these machines:
- Date: 1882
A dynamo, originally another name for an electrical generator, now means a generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter. They are rarely used for power generation now because of the dominance of alternating current, the disadvantages of the commutator, and the ease of converting alternating to direct current using solid state methods.
The word still has some regional usage as a replacement for the word generator. A small electrical generator built into the hub of a bicycle wheel to power lights is called a Hub dynamo, although these are invariably AC devices.