Nikola Tesla (1856-1943), Serb-US physicist and electrical engineer. Tesla was educated at Graz and Prague, but in 1884 he emigrated to the USA. For a while he worked with Edison, but soon left to work on his own. He developed the alternating current (a.c.) induction motor, and helped advance a.c. power generation and transmission. He also worked on high-frequency a.c. currents, inventing the Tesla Coil, a transformer in which the primary and secondary coils are in resonance. He used it to create electric sparks 40 metres long, and in 1899 lit 200 electric lamps over 25 miles without wires. The SI unit of magnetic flux density is named for him. Engraving from Discoveries and Inventions of the Nineteenth Century (1898).