John Hopkinson

John Hopkinson (1849 to 1898) was a British physicist and electrical engineer, a Fellow of the Royal Society and twice President of the Institution of Electrical Engineers, in 1890 and 1896. Born in Manchester, the eldest of five children of a mechanical engineer, he was educated at Queenwood School in Hampshire and Owens College in Manchester, won a scholarship to Trinity College, Cambridge, in 1867 and graduated in 1871 as Senior Wrangler. Rather than follow a purely academic career he chose engineering, and in 1872 became an engineering manager in the lighthouse department of Chance Brothers in Smethwick. He was elected to the Royal Society in 1877 for applying Maxwell's theory of electromagnetism to problems of electrostatic capacity and residual charge, and in 1882 he patented the three-wire, or three-phase, system for distributing electrical power. He also worked on electromagnetism and electrostatics, and Hopkinson's law, the magnetic counterpart of Ohm's law, is named after him. In 1890 he became professor of electrical engineering at King's College London, where he also directed the Siemens Laboratory.