Transformer
The transformer makes modern power transmission possible, changing voltages up or down with very little loss of power. Its development dates back to the early nineteenth century, when, in 1820, Hans Christian Oersted (1775-1851) discovered that an electric current in a conductor created a magnetic field and started a flurry of research into the area of electromagnetism. Michael Faraday decided to reverse Oersted's discovery by using a magnetic field to create an electric current. In 1831, he discovered that the current sent through a wire coil set up "magnetic lines of force" that expanded outward and affected a nearby second coil. By alternating the expansion and collapse of the lines, he could induce an alternating current (AC) of electricity in the second coil. Experimenting with the number of turns of wire in his coil, Faraday discovered that if the secondary coil had twice as many turns as the primary, the electric current was doubled; if the secondary coil had half as many turns, the current was cut in half. Thus the transformer was born, and with great efficiency was able to "step up" low-generated current for high-current transmission and step it down again at its destination.
The scientific community took little notice of Faraday's work for half a century, because their attention had been fixed on direct current (DC) since the invention of the electric battery by Alessandro Volta in 1800. By the 1880s, Thomas Edison was lighting electric street lamps with DC dynamos. However, there were disadvantages to DC, including the power loss caused by arcing in the dynamos and a limited transmission distance due to resistance in the wires. In England, Lucien H. Gaulard and John D. Gibbs used a transformer (which they called a secondary generator) to power incandescent lamps in an AC arc-lighting system in 1882. Though impractical, the Gaulard-Gibbs equipment did encourage others to experiment.
The prototype for today's lighting systems was designed by three Hungarian engineers, Max Déri, Otto T. Bláthy and Karl Zipernowski, who demonstrated their transformer in 1885 at the Hungarian National Exhibition in Budapest. In 1884, Croatian inventor Nikola Tesla began working for Edison, and repeatedly tried to sway him to the advantages of AC. Failing in his attempts, Tesla took his ideas to the industrialist George Westinghouse. The ultimate success of Tesla and Westinghouse at the 1893 Columbia Exposition in Chicago ended the DC monopoly on electric power supply. In 1895 the first hydroelectric AC power generator was build at Niagara Falls, using a generation (step-up) transformer to conduct the current many miles over high tension wires to a transmission (step-down) transformer for distribution to customers.
The quality of transformers has continued to improve with better construction materials. A good generator has a core with high permeability--that is, it produces a high number of lines of magnetic force. Resistivity minimizes energy lost to eddy currents. A high saturation level insures the ability of the material to amplify the magnetic force to a high plateau. A quality generator also minimizes loss of efficiency due to hysteresis, a "magnetic memory" that wastes energy from a lag in the AC cycle, due to the build up of a magnetic influence.
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