Electric alternator

An alternator consists of a magnet turning in the middle of a copper wire coil. The coil’s electrons are set in motion each time the magnet revolves. Since the magnet has positive and negative poles, the electrons change direction alternately, producing an alternating current, preferred to direct current because it is easier to convey over long distances. An energy source was needed to turn the generator’s magnet, provided either by a steam engine or a watermill. This late 19th-century alternator was connected to a Francis turbine used for water falls of around ten metres. Turning at 750 revolutions per minute, it generated a 100-hertz, 2,440-volt single-phase current.