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41 Joubert, Jules François
SUBJECT AREA: Electricity[br]b. 1834 Tours, Franced. 1910 Paris, France[br]French physicist, investigator of alternating-current wave-forms.[br]Joubert became Professor of Physics in the Collège Rollin, Paris, in 1874, a position he held until 1888. He was at one time General Secretary of the Société Française de Physique. In collaboration with Pasteur he began studies into the theories of germs and bacteria. In 1880 Joubert carried out research on wave-forms in alternating-current arc-lighting circuits. Reinventing a method previously used by earlier experimenters, including Wheatstone, he was, by a mechanical sampling technique, able to determine the voltage at different points in the cycle. By using a rotating contact on the alternator shaft, the angular position of which could be varied, the whole of the wave-form could be delineated. This successful technique was widely used for some thirty years.[br]Bibliography1880, "Sur les courants alternatifs et la force électromotive de l'arc électrique", Journal of Physics 9:297–303 (describes his experiments).Further Reading"Investigation of alternating current arcs", Electrician (1880) 5:151–2 (a report on Joubert's method).V.J.Phillips, 1987, Waveforms, Bristol (an extensive account of early methods of wave-form observation).W.Bulloch, 1938, The History of Bacteriology, Oxford; 1979, repub. New York.See also: Duddell, William du BoisGWBiographical history of technology > Joubert, Jules François
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42 Volta, Alessandro Giuseppe Antonio Anastasio
SUBJECT AREA: Electricity[br]b. 18 February 1745 Como, Italyd. 5 March 1827 Como, Italy[br]Italian physicist, discoverer of a source of continuous electric current from a pile of dissimilar metals.[br]Volta had an early command of English, French and Latin, and also learned to read Dutch and Spanish. After completing studies at the Royal Seminary in Como he was involved in the study of physics, chemistry and electricity. He became a teacher of physics in his native town and in 1779 was appointed Professor of Physics at the University of Pavia, a post he held for forty years.With a growing international reputation and a wish to keep abreast of the latest developments, in 1777 he began the first of many travels abroad. A journey started in 1781 to Switzerland, Germany, Belgium, Holland, France and England lasted about one year. By 1791 he had been elected to membership of many learned societies, including those in Zurich, Berlin, Berne and Paris. Volta's invention of his pile resulted from a controversy with Luigi Galvani, Professor of Anatomy at the University of Bologna. Galvani discovered that the muscles of frogs' legs contracted when touched with two pieces of different metals and attributed this to a phenomenon of the animal tissue. Volta showed that the excitation was due to a chemical reaction resulting from the contact of the dissimilar metals when moistened. His pile comprised a column of zinc and silver discs, each pair separated by paper moistened with brine, and provided a source of continuous current from a simple and accessible source. The effectiveness of the pile decreased as the paper dried and Volta devised his crown of cups, which had a longer life. In this, pairs of dissimilar metals were placed in each of a number of cups partly filled with an electrolyte such as brine. Volta first announced the results of his experiments with dissimilar metals in 1800 in a letter to Sir Joseph Banks, President of the Royal Society. This letter, published in the Transactions of the Royal Society, has been regarded as one of the most important documents in the history of science. Large batteries were constructed in a number of laboratories soon after Volta's discoveries became known, leading immediately to a series of developments in electrochemistry and eventually in electromagnetism. Volta himself made little further contribution to science. In recognition of his achievement, at a meeting of the International Electrical Congress in Paris in 1881 it was agreed to name the unit of electrical pressure the "volt".[br]Principal Honours and DistinctionsFRS 1791. Royal Society Copley Medal 1794. Knight of the Iron Crown, Austria, 1806. Senator of the Realm of Lombardy 1809.Bibliography1800, Philosophical Transactions of the Royal Society 18:744–6 (Volta's report on his discovery).Further ReadingG.Polvani, 1942, Alessandro Volta, Pisa (the best account available).B.Dibner, 1964, Alessandro Volta and the Electric Battery, New York (a detailed account).C.C.Gillispie (ed.), 1976, Dictionary of Scientific Biography, Vol. XIV, New York, pp.66–82 (includes an extensive biography).F.Soresni, 1988, Alessandro Volta, Milan (includes illustrations of Volta's apparatus, with brief text).GWBiographical history of technology > Volta, Alessandro Giuseppe Antonio Anastasio
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