Electric generator

1831 Electric generator

The book of science

Tom Sharp

Michael Faraday electromagnetism Electric generator

Electric generator

Before Faraday, electric generators generated a static charge using friction or electrostatic induction, producing a high voltage but a low current. Before Faraday invented the electric generator, he discovered its operating principle, the law of induction. A moving magnetic field creates a separation of charge in an electric circuit. All Faraday had to do was to rotate a copper disk through the middle of a horseshoe magnet.

Electric generators

The Faraday disc, also called a homopolar generator, generated a direct current. The next year Hippolyte Pixii added multiple windings and a commutator to generate a pulsed direct current. John Stephen Woolrich designed the first electric generator used in an industrial process in 1844. By 1867, Charles Wheatstone, Werner von Siemens, and Samuel Alfred Varley had patented their own dynamos. Michael Faraday also built the first alternating current generator, his heteropolar “rotating rectangle.” Commercial alternators quickly followed, by James Gordon in 1882, by Lord Kelvin and Sebastian Ziani de Ferranti in 1882, by William Stanley Jr. at Westinghouse Electric in 1886, and in London the first modern power station by Ferranti in 1887.


Atmospheric pressure and wind, gravity and water, generators convert natural kinetic energies into electric forces to charge my car’s batteries. On the street, my car’s motor converts electricity from the batteries into kinetic energy— zero to thirty-five in ten seconds. Then I release the accelerator to turn the motor into a generator, converting the car’s kinetic energy back into electricity that recharges the batteries. DC to AC, AC to DC, kinetic to electric, electric to kinetic, alternating forms of energy keep us moving, keep us happy, though losses add up with every conversion.

Discoveries and inventions like this don’t happen in a vacuum. The operation of Michael Faraday’s original generator was inefficient, but others quickly improved and varied the design. André-Marie Ampère suggested that Pixii use a communtator to convert his AC generator to a pulsed DC generator. Faraday had a look at Woolrich’s generator at Elkington Silver Electroplating Works in Birmingham and “expressed his intense delight.” James Clerk Maxwell mathematically formalized Faraday’s discoveries and James Gordon worked under Maxwell’s supervision at the Cavendish Laboratory.

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