Homopolar motor is a direct current electric motor that you can make at home in minutes. Is was invented by Michael Faraday in 1821. and driven by the principle of the Lorentz force.

Principle: A conductor with a current flowing through it when placed in a magnetic field which is perpendicular to the current feels a force in the direction perpendicular to both the magnetic field and the current. This force provides a torque around the axis of rotation.
Like most electro-mechanical machines, a homopolar motor is reversible: if the conductor is turned mechanically, then it will operate as a homopolar generator, producing a direct current voltage between the two terminals of the conductor.

For more details please watch this video: