From the Quarterly Journal of Science, Vol XII, 1821
Faraday Motor from the collection1830's
As is so often the case with invention, the credit for development of the electric motor belongs to more than one individual. It was through a process of development and discovery beginning with Hans Oersted's discovery of electromagnetism in 1820 and involving additional work by William Sturgeon, Joseph Henry, Andre Marie Ampere, Michael Faraday, Thomas Davenport and a few others.
Using a broad definition of "motor" as meaning any apparatus that converts electrical energy into motion, most sources cite Faraday as developing the first electric motors, in 1821. They were useful as demonstration devices, but that is about all, and most people wouldn't recognize them as anything resembling a modern electric motor. There are several Faraday motors in the collection.
The motors were constructed of a metal wire suspended in a cup of mercury (See illustration at right). Protruding up from the bottom of the cup was a permanent magnet. In the left cup the magnet was attached to the bottom with a piece of thread and left free to move, while the metal wire was immobile. On the right side, the magnet was held immobile and the suspended wire was free to move.
When current from a Volta pile was applied to the wire, the circuit was completed via the mercury ( a good conductor of electricity) and the resulting current flowing through the wire produced a magnetic field. The electromagnetic field interacted with the existing magnetic field from the permanent magnet, causing rotation of the magnet on the left, or of the wire on the right.