The principle later called Faraday's law, is that an electromotive force is generated in an electrical conductor which encircles a varying magnetic flux.
The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and generators have many similarities.
Many motors can be mechanically driven to generate electricity and frequently make acceptable manual generators.
The Woolrich Electrical Generator of 1844, now in Thinktank, Birmingham Science Museum, is the earliest electrical generator used in an industrial process.
The modern dynamo, fit for use in industrial applications, was invented independently by Sir Charles Wheatstone, Werner von Siemens and Samuel Alfred Varley.
The use of electromagnets rather than permanent magnets greatly increased the power output of a dynamo and enabled high power generation for the first time.
This invention led directly to the first major industrial uses of electricity.The current flowed out through the sliding spring contact m, through the external circuit, and back into the center of the disk through the axle.The operating principle of electromagnetic generators was discovered in the years of 1831–1832 by Michael Faraday.While current was induced directly underneath the magnet, the current would circulate backwards in regions that were outside the influence of the magnetic field.This counterflow limited the power output to the pickup wires, and induced waste heating of the copper disc.Wire windings became a basic feature of all subsequent generator designs.