Charles Wheatstone

Charles Wheatstone was an English physicist and inventor who lived from February 6, 1802 to October 19, 1875 and worked across an unusually wide range of instruments, from the telegraph to the concertina, before turning to the electric generator late in his career. In the winter of 1866 and 1867 he arrived independently at the self-exciting principle of the dynamo-electric machine, in which a generator's own output current can build up its own magnetic field rather than needing a separate battery to start it, and he exhibited a working example at the Royal Society on February 4, 1867. Two other engineers reached the same principle at almost the same moment: the English electrician Samuel Alfred Varley had already patented it on December 24, 1866, and the German engineer Werner Siemens announced it publicly on January 17, 1867, so credit for the self-exciting dynamo is shared three ways among Varley, Siemens and Wheatstone rather than belonging to any one of them alone. The self-exciting principle they all converged on removed the last major obstacle to building large, reliable electric generators, and it underlies the dynamos and alternators that generate almost all of the world's electricity today.