Electric motor: Difference between revisions

Before modern electromagnetic motors, experimental motors that worked by electrostatic force were investigated. The first electric motors were simple [[Electrostatic motor|electrostatic devices]] described in experiments by Scottish monk [[Andrew Gordon (Benedictine)|Andrew Gordon]] and American experimenter [[Benjamin Franklin]] in the 1740s.<ref name="Gordon2">Tom McInally, The Sixth Scottish University. The Scots Colleges Abroad: 1575 to 1799 (Brill, Leiden, 2012) p. 115</ref><ref>Oleg D. Jefimenko (1973). ''Electrostatic Motors, Their History, Types, and Principles of Operation'', Electret Scientific Company. pp. 22–45</ref> The theoretical principle behind them, [[Coulomb's law]], was discovered but not published, by [[Henry Cavendish]] in 1771. This law was discovered independently by [[Charles-Augustin de Coulomb]] in 1785, who published it so that it is now known withby his name.<ref>{{Cite journal|last=Guarnieri|first=M.|year=2014|title=Electricity in the age of Enlightenment|journal=IEEE Industrial Electronics Magazine|volume=8|issue=3|pages=60–63|doi=10.1109/MIE.2014.2335431|s2cid=34246664}}</ref> Due to the difficulty of generating the high voltages they required, electrostatic motors were never used for practical purposes.

The[[Michael Faraday]] gave the first demonstration of the effect with a rotary motion was given by [[Michael Faraday]] on 3 September 1821 in the basement of the [[Royal Institution]].<ref name="Electric Motion">{{cite news |title=The birth of electric motion |url=https://www.rigb.org/explore-science/explore/blog/birth-electric-motion |access-date=19 July 2022 |work=Royal Institution}}</ref> A free-hanging wire was dipped into a pool of mercury, on which a [[Permanent magnet|permanent magnet (PM)]] was placed. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire.<ref name="SparkMuseum (Motor)2">{{cite conference|title=The Development of the Electric Motor|url=http://www.sparkmuseum.com/MOTORS.HTM|publisher=SparkMuseum|archive-url=https://web.archive.org/web/20130306085840/http://www.sparkmuseum.com/MOTORS.HTM|archive-date=6 March 2013|access-date=12 February 2013|book-title=Early Electric Motors|url-status=live}}</ref> Faraday published the results of his discovery in the ''[[Quarterly Journal of Science]]'', and sent copies of his paper along with pocket-sized models of his device to colleagues around the world so they could also witness the phenomenon of electromagnetic rotations.<ref name="Electric Motion"/> This motor is often demonstrated in physics experiments, substituting [[brine]] for (toxic) mercury. [[Barlow's wheel]] was an early refinement to this Faraday demonstration, although these and similar [[homopolar motor]]s remained unsuited to practical application until late in the century.