Ernst Werner Siemens (13.12.1816-6.12.1892) — a German physicist, electrical engineer and entrepreneur, a member of the Berlin Academy of Sciences (1874). Born in Lenthe near Hanover. He graduated from the Berlin Artillery School, but soon left a military career and took up inventing. Together with J. Halske he constructed an electric telegraph (patented in Prussia in 1847) and began to take orders and contracts for telegraph installations. The profits from these contracts, and especially from building the telegraph line from St Petersburg to Sevastopol, enabled Siemens to turn a small Berlin workshop into a large factory. He was the founder and chief owner of the electrical engineering concerns Siemens and Halske and Siemens and Schuckert.
He carried out large-scale developments in electrical engineering and became the founder of the electrical industry. He invented a machine for applying rubber insulation to wires, created (1860) the mercury standard of resistance, measured the electrical conductivity of various metals and its dependence on temperature, and the dielectric constants of many substances. He improved (1860) the resistance box. In 1867 he proposed replacing the steel magnets in induction electric machines with electromagnets and developed (independently of others) a self-excited electric generator. He built the first tram (1879), constructed an electric pyrometer (1869), created an industrial design of electric melting furnace (1878) and a selenium photometer (1887). The unit of resistance in the International System of Units, the siemens, is named after Siemens.
A corresponding member of the St Petersburg Academy of Sciences (1882). One of the founders of the first physico-technical institute (Berlin, 1888).