Every light you switch on is his. Nikola Tesla's alternating current runs the world's grids, his coil still crackles in laboratories, and his name rides on electric cars — yet he died alone and nearly penniless in a New York hotel room, feeding pigeons in the park across the street. No inventor in history has given so much and kept so little.
Toroid — high-voltage terminalSecondary coilPrimary coilSpark gapEarth ground The Tesla coil — lightning from resonance The breakthrough Tesla's breakthrough was a vision — literally. As a student in Graz he watched a direct-current dynamo spark and stutter, and saw in a flash the solution: a rotating magnetic field produced by alternating currents, driving a motor with no brushes, no commutator, no sparks. The induction motor. In 1888 he laid out the complete polyphase system — generation, transmission, motors — the full architecture of the modern power grid, in a burst of forty-odd patents.
