Gramme dynamo, c 1870.
© Science Museum / Science & Society Picture Library
A dynamo generator made by the Belgian Zenobe Theophile Gramme (1826-1901). This early dynamo generated enough electrical current for large-scale applications such as powering lights in factories. It was steam-driven, produced a direct current (dc), and unlike its predecesors it did not overheat when in continuous use. The dynamo was, however, costly to maintain as the commutator and brush contacts wore out through use. Gramme manufactured this dynamo from 1871 onward, making it the first electric generator to be used commercially.