Volta, Alessandro Guiseppe Antonio Anastasio (physicist)


(1745-1827) Italian Experimental Physicist (Classical Electromagnetism)

Alessandro Volta was the pioneer in the field of electricity who built the voltaic pile, the forerunner of the modern electric battery. In a famous debate with Luigi Galvani, he successfully argued that the source of the electric current generated when metals are brought into contact with the muscles of a frog are the metals rather than the frog. An ingenious experimenter, he also invented the electrophorus, a device for producing charges of static electricity.

He was born in Como, in Lombardy, Italy, on February 18, 1745, into a noble family. When young Alessandro failed to develop speech until the age of four, his family was sure he was intellectually impaired. By age seven, however, when his father died, he had caught up to his age group. Educated at religious schools, he showed an early aptitude for science, and when he was 14, he decided to become a physicist. The theory of electricity, which he learned about by studying the work of Benjamin Franklin, so entranced him that he composed an excellent Latin poem on the subject. At the age of 20, he began experimenting with static electricity. His renown as a scientist grew rapidly, leading to his appointment in 1774 as principle of the gymnasium in Como, where, the next year, became a professor of experimental physics.

Volta’s work on static electricity culminated in 1775, with his invention of the electrophorus. His extensive knowledge of the nature and quantity of electrostatic charge generated by different materials enabled him to develop a fairly simple device for the production of charges: it consisted of one metal plate covered with ebonite and a second metal plate with an insulated handle. The ebonite-covered plate is rubbed and given a negative electric charge. If the plate with a handle is placed over it, a positive electric charge is attracted to the lower surface, a negative charge repelled to the upper. The negative charge is built up in the plate with the handle. Today’s electrical condensers are based on this type of charge-accumulating machine. Volta also realized from his electrostatic experiments that the quantity of charge produced is proportional to the product of its electrostatic potential, which he measured with an electrometer of his own invention, and the capacity of the conductor.

At this point, Volta’s interests veered toward the study of air and gases. By isolating and examining the properties of marsh gas found in Lake Maggiore (adjacent to Lake Como), he discovered methane. In another study, he accurately estimated the proportion of oxygen in the air by exploding air with hydrogen to remove the oxygen. Volta would return to these investigations 20 years later, making the discovery that the vapor pressure of a liquid depends only on temperature and is independent of atmospheric pressure, a principle that the British chemist and physicist John Dalton would later enunciate in his law of partial pressures.

However substantial these achievements, they were only a digression in Volta’s pursuit of the mysteries of electricity. In 1778, he transferred his laboratory from Como to Padua, where he accepted a position as professor of experimental physics. He would remain in Padua until 1819, surviving the conflict between Austria and France that engulfed the region. His considerable political acumen enabled him to hang on to his position no matter who was in charge and carry on his scientific work.

Volta’s path to his great discovery began in 1791, when his friend Luigi Galvani sent him his papers describing some interesting results: Gal-vani had produced contractions in the muscles of dead frogs by placing two different metals (brass and iron) into contact with the muscle and with each other. Galvani believed that the contractions had their source in the frogs’ muscles. Volta was not so sure. He successfully repeated Galvani’s experiments, using different metals and different animals, and concluded that the source of the electricity lay in the junction of the metals. In the ensuing controversy between the two Italians, the French physicist charles augustin coulomb was a strong advocate of Volta’s position, which prevailed as evidence in its favor accumulated. This included an experiment in which Volta placed the metals on his tongue and produced an unpleasant sensation. He attributed this effect to electricity and went on to compose a list of metals in order of their electricity production, based on the strength of the sensation they made on his tongue. In this way, he derived what came to be known as the electromotive series, the arrangement of chemical elements in order of their standard electrode potentials.

From here, it would be but a brief step to his discovery of the voltaic pile. In 1796, attempting to measure the electricity produced by different metals, he tried piling disks of metals on top of one another and found that they had to be separated by a moist conductor to produce a current. His work was disrupted by political upheavals, but by 1800 he had created his prototype of the modern electric battery. In that year he wrote to the president of the Royal Society, Joseph Banks, to describe two arrangements of conductors that produced an electric current. One was a pile of silver and zinc disks separated by cardboard moistened with brine, the other was a series of glasses of salty or alkaline water in which bimetallic curved electrodes were dipped. This was the first electric battery.

Volta’s breakthrough, which meant that high electric currents could now be produced, was greeted with immense excitement. Volta traveled to Paris in 1801 to demonstrate his discoveries to Napoleon, who, duly impressed, made him a count and awarded him a pension. He was the recipient of many honors, including membership in England’s Royal Society, which honored him with its Copley medal and decoration by the Legion of Honor. In 1810, he was made a senator of the kingdom of Lombardy and given the title of count. Volta retired in 1819. On March 5, 1827, he died in Como.

Volta’s invention of the battery signaled the beginning of a century of discoveries, which would establish the dynamics of electricity and electromagnetism and harness their power in ways that would transform civilization. The unit of electric potential, or electromotive force, is named the volt in his honor.

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