The device Michael Faraday invented in 1831 that is also called a homopolar generator is the Faraday disc.
Faraday’s machine used a copper disc rotating between the poles of a horseshoe magnet. Electrical current was collected between the disc’s centre and its rim, demonstrating that mechanical motion and magnetism could produce electricity. It was one of the earliest electromagnetic generators and helped establish the practical meaning of electromagnetic induction.
The Faraday disc is also called a Faraday wheel, unipolar generator, or disk dynamo. “Dynamo” is a broader term for an electrical generator, so it is related but less precise than Faraday disc. An electric motor does the reverse job by converting electrical energy into motion, while an induction coil produces high-voltage pulses rather than continuous direct current from a rotating disc.
The original disc was inefficient as a power source because of electrical losses and sliding contacts, but its design remains important in the history of generators and high-current homopolar machines.