English: Model of Faraday's disk, the first electric generator, invented by British scientist Michael Faraday in 1831. It consists of a copper disk between the poles of a horseshoe magnet. When the disk is turned with the crank, a current of electrons flows radially from the center of the disk to the rim, due to Faraday's law of induction. This is picked up by a springy contact pressed against the rim of the disk. The current flows through an external circuit and returns to the center of the disk through the axle. Exhibit in the National Museum of Nature and Science, Tokyo, Japan. Photography was permitted in the museum without restriction.