Heinrich Daniel Ruhmkorff was a German instrument maker who commercialised the induction coil.
Ruhmkorff was born in Hanover. He changed the "ü" to "u" in his name when living abroad. After an apprenticeship with a German mechanic, he moved to England. Biographies say that he worked with the inventor Joseph Bramah, but this is unlikely since Bramah died in 1814. He may, though, have worked for the Bramah company. In 1855, he set up a shop in Paris, where he gained a reputation for the high quality of his electrical apparatus.
Although Ruhmkorff is often credited with the invention of the induction coil, it was in fact invented by Nicholas Callan in 1836. Ruhmkorff's first coil, which he patented in 1851, utilized long windings of copper wire to achieve a spark of approximately 2 inches in length. In 1857, after examining a greatly improved version made by an American inventor, Edward Samuel Ritchie, Ruhmkorff improved his design, using glass insulation and other innovations to allow the production of sparks more than 30 centimetres long.