Worlds of David Darling
Encyclopedia of Science
   
Home > Encyclopedia of Science

Volta, Alessandro Guiseppe Antonio Anastasio (1745–1827)





Alessandro Volta
Italian physicist who made the first simple cell and invented the electrophorus. He served as professor first at his native Como, and then at Pavia. Most of his early experiments were conducted with the minute quantities of electricity provided by friction (static electricity). With the electrophorus he improved the methods of making frictional electricity but the electrophorus could do no more than produce sparks – sudden movements of electrical charge. It was an entertaining toy with no practical uses, for the currents it produced flowed for only a fraction of a second, and were still about a million times smaller than those we use today for heating and lighting. Very little could be done with these tiny amounts.

One of the few possible fields of study, and which attracted considerable interest at the time, was "animal electricity," the effects of passing electric current through animal tissue – usually frog's legs. Another Italian scientist, Luigi Galvani, had connected a copper rod to the nerve in a frog's leg, and a rod of a different metal, iron, to the muscle. When the ends of the two pieces of metal were placed in contact, the muscle twitched, as it did when an electric current passed through. Galvani thought that electricity had been produced, in some mysterious way, by the twitching of the muscle.

Volta's Piles
However, Volta realized that the nerve and muscle were merely responding to an electric shock. The important thing was that two different metals had been joined at one end, and separated at the other by a conducting solution (the weak electrolytic solution in the frog's leg). Animal tissue was not necessary at all. In 1799 Volta made the first simple cell by dipping rods of copper and zinc into brine, and joining them. An electric current flowed through the circuit that joined them. The current was far larger, and lasted far longer, than anything experienced before. High potential differences (voltages) could be obtained by connecting simple cells in series. This idea led to the voltaic pile, which consisted of alternate layers of zinc and copper disks, separated by flannel disks soaked in brine or acid.

Credit is given to Volta for the invention of the simple cell, but he never found the right explanation for its working. He wrongly ascribed the current to the actual contact of the two metals, whereas it in fact results from chemical action of the electrolyte on the zinc rod.

The discovery was acclaimed immediately, and in 1801 Volta went to Paris to demonstrate his so-called "contact" electricity to the Emperor Napoleon. Later, the unit of electric potential, the volt, was named after him.

Although Volta himself was interested in developing his batteries than applying them, the voltaic cell rapidly became used by scientists everywhere as a powerful tool for research. The currents produced with the aid of voltaic cells led to the discovery of the heating, chemical, and magnetic effects of electricity.


Related entry

   • history of electricity


Related category

   • PHYSICISTS