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power excited great public interest. As late as 1893, the beauty of incandescent electric light bulbs left viewers awestruck at the Worlds Columbian Exposition in Chicago.The glow of a light bulb does not come from static electricity, which arises from electrical charge that is at rest and thus incapable of performing useful work,but from electric current, which is the flow of electrical charge in the form of elec- trons. Nearly every important application of electricity, from illumi- nation to computation, depends on current.

Electric current is not a human invention. It flows in a lightning flash and in the animal world. Plato,Aristotle, and the Roman natural- ist Pliny the Elder all wrote about the Mediterranean creature called the torpedo fish,which moves normally but makes other fish sluggish. Now we know that the torpedo fish is a natural electrical source that sends current through its victims to narcotize them.

The first observations that led to the human use of current were made in an animal; they were part of the research carried out in the 1780s by Luigi Galvani, the anatomy professor at the University of Bologna who studied how electricity made a dissected frogs legs twitch. Galvanis conclusion, that a form of electricity arose in the frog, inspired AlessandroVolta, a physics professor at the University of Pavia, to carry out further experiments.

Voltas researches showed that Galvanis belief in animal electric- ityhad no basis, an important outcome in itself, and had another far- reaching effect. This was a fundamental breakthrough that Volta announced in 1800the Voltaic pile, a stack of alternating zinc and copper disks, separated by cloth or cardboard soaked in salt water. That was the first electrical battery, a device to produce a steady flow of current. Its importance was immediately recognized. Napoleon observed Voltas invention at a command performance in 1801, and went on to name Volta a senator and a count of the kingdom of Lombardy. Scientists quickly applied this new resource.Within a year, Humphry Davy of the Royal Institution in London attached two carbon electrodes to a massive battery and obtained an intense white glow, thus discovering the carbon arc, the earliest form of artificial electrical lighting.

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