The homopolar motor was originally invented by Michael Faraday in 1821 and is the oldest type of electric motor. In this setup, the copper wire connects the positive battery terminal to the magnet at the negative battery terminal, thus completing the circuit. Due to the close proximity of the magnet at the bottom of the battery, current flows in the presence of a magnetic field. When current flows in a magnetic field, it experiences a Lorentz force that acts perpendicular to both the current's direction and the direction of the magnetic field. Sources: PhysicsCentral and Physicsfun