Electromagnetism
Discovered in 1821 by scientists Hans Christian Ostred. Michael Faraday would later come up with many of the theories about it we use to day and, of coure, help invent the homopolar motor.
Homopolar Motor
Michael Faraday went to work creating the motor later that year. Faraday demonstrated the homopolar motor in 1821 at the Royal Institution in London.
Use Through History
Although the homopolar motor has potential to be used in a myriad of ways, because of the limitation of the lack of an off switch, the homopolar has seen little application since it's conception. The most direct use of the motor came in the 1930s when it was put to use as an assembly machine in steel mills. The scientific principles behind it, however, have played a part in the creation of many things including wind turbines, generators, and railguns.