Electric charge: Difference between revisions

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Around 1663 [[Otto von Guericke]] invented what was probably the first [[electrostatic generator]], but he did not recognize it primarily as an electrical device and only conducted minimal electrical experiments with it.<ref>{{cite journal|last1=Heathcote|first1=N.H. de V.|title=Guericke's sulphur globe |journal=Annals of Science |date=1950| volume=6|issue=3| page=304|doi=10.1080/00033795000201981}}<br>{{cite book |title=Electricity in the 17th and 18th centuries: a study of early Modern physics |last=Heilbron |authorlink=John L. Heilbron |first=J.L. |year=1979 |publisher=[[University of California Press]] |isbn=0-520-03478-3 |pages=215–218 |url=https://books.google.com/books?id=UlTLRUn1sy8C&pg=PA215}}</ref> Other European pioneers were [[Robert Boyle]], who in 1675 published the first book in English that was devoted solely to electrical phenomena.<ref name=Baigrie20>{{cite book|last=Baigrie|first=Brian |title=Electricity and magnetism: A historical perspective|year=2007|publisher=Greenwood Press|location=Westport, CT|page=20}}</ref> His work was largely a repetition of Gilbert's studies, but he also identified several more "electrics",<ref name=Baigrie21>{{cite book|last=Baigrie|first=Brian |title=Electricity and magnetism: A historical perspective|year=2007|publisher=Greenwood Press|location=Westport, CT|page=21}}</ref> and noted mutual attraction between two bodies.<ref name=Baigrie20/>
 
In 1729 [[Stephen Gray (scientist)|Stephen Gray]] was experimenting with [[static electricity]], which he generated using a glass tube. He noticed that a cork, used to protect the tube from dust and moisture, also became electrified (charged). Further experiments (e.g, extending the cork by putting thin sticks into it) showed – forshowed—for the first time – thattime—that electrical effluvia (as Gray called it) could be transmitted (conducted) over a distance. Gray managed to transmit charge with twine (765 feet) and wire (865 feet).<ref name=Baigrie27>{{cite book|last=Baigrie|first=Brian |title=Electricity and magnetism: A historical perspective|year=2007|publisher=Greenwood Press|location=Westport, CT|page=27}}</ref> Through these experiments, Gray discovered the importance of different materials, which facilitated or hindered the conduction of electrical effluvia. [[John Theophilus Desaguliers]], who repeated many of Gray’s experiments, is credited with coining the terms [[electrical conductor|conductors]] and [[electrical insulation|insulators]] to refer to the effects of different materials in these experiments.<ref name=Baigrie27/> Gray also discovered electrical induction (i.e., where charge could be transmitted from one object to another without any direct physical contact). For example, he showed that by bringing a charged glass tube close to, but not touching, a lump of lead that was sustained by a thread, it was possible to make the lead become electrified (e.g., to attract and repel brass filings).<ref name=Baigrie28>{{cite book|last=Baigrie|first=Brian |title=Electricity and magnetism: A historical perspective|year=2007|publisher=Greenwood Press|location=Westport, CT|page=28}}</ref> He attempted to explain this phenomenon with the idea of electrical effluvia.<ref>{{cite book |last= Heilbron| first= J.L.|title= Electricity in the 17th and 18th Centuries: A Study of Early Modern Physics|publisher= University of California Press|year= 1979|page= 248|isbn= 978-0-520-03478-5|url= https://books.google.com/?id=UlTLRUn1sy8C&pg=PA248}}</ref>
 
Gray’s discoveries introduced an important shift in the historical development of knowledge about electric charge. The fact that electrical effluvia could be transferred from one object to another, opened the theoretical possibility that this property was not inseparably connected to the bodies that were electrified by rubbing.<ref name=Baigrie35>{{cite book|last=Baigrie|first=Brian |title=Electricity and magnetism: A historical perspective|year=2007|publisher=Greenwood Press|location=Westport, CT|page=35}}</ref> In 1733 [[Charles François de Cisternay du Fay]], inspired by Gray's work, made a series of experiments (reported in ''Mémoires de l'[[Académie Royale des Sciences]]''), showing that more or less all substances could be 'electrified' by rubbing, except for metals and fluids<ref>{{cite book |last1=Roller |first1=Duane |author-link1= |last2=Roller |first2=D.H.D.|date=1954 |title=The development of the concept of electric charge: Electricity from the Greeks to Coulomb |url=https://archive.org/details/developmentofcon0000roll|url-access=registration |location=Cambridge, MA |publisher=[[Harvard University Press]] |page=[https://archive.org/details/developmentofcon0000roll/page/40 40] |isbn=}}</ref> and proposed that electricity comes in two varieties that cancel each other, which he expressed in terms of a two-fluid theory.<ref>[http://www.sparkmuseum.com/BOOK_DUFAY.HTM Two Kinds of Electrical Fluid: Vitreous and Resinous – 1733. Charles François de Cisternay DuFay (1698–1739)] {{webarchive|url=https://web.archive.org/web/20090526211225/http://www.sparkmuseum.com/BOOK_DUFAY.HTM |date=2009-05-26}}. sparkmuseum.com</ref> When [[glass]] was rubbed with [[silk]], du Fay said that the glass was charged with ''[[glass|vitreous]] electricity'', and, when amber was rubbed with fur, the amber was charged with ''[[resin]]ous electricity''. Another important two-fluid theory from this time was proposed by [[Jean-Antoine Nollet]] (1745).<ref>{{cite book |last= Heilbron| first= J.L.|title= Electricity in the 17th and 18th Centuries: A Study of Early Modern Physics|publisher= University of California Press|year= 1979|pages= 280–289|isbn= 978-0-520-03478-5|url= https://books.google.com/?id=UlTLRUn1sy8C&pg=PA169}}</ref> In 1839, [[Michael Faraday]] showed that the apparent division between [[static electricity]], [[electric current|current electricity]], and [[bioelectricity]] was incorrect, and all were a consequence of the behavior of a single kind of [[electricity]] appearing in opposite [[electrical polarity|polarities]]. It is arbitrary which polarity is called positive and which is called negative. Positive charge can be defined as the charge left on a glass rod after being rubbed with silk.<ref>Roald K. Wangsness (1986) ''Electromagnetic Fields'' (2nd Ed.). Wiley. {{ISBN|0-471-81186-6}}.</ref>
 
A second piece of glass rubbed with a second piece of resin, then separated and suspended near the former pieces of glass and resin causes these phenomena:
* The two pieces of glass repel each other.
* Each piece of glass attracts each piece of resin.
* The two pieces of resin repel each other.
 
This attraction and repulsion is an ''electrical phenomenon'', and the bodies that exhibit them are said to be ''electrified'', or ''electrically charged''. Bodies may be electrified in many other ways, as well as by friction. The electrical properties of the two pieces of glass are similar to each other but opposite to those of the two pieces of resin: The glass attracts what the resin repels and repels what the resin attracts.
 
==See also==
* [[SI electromagnetism units]]
* [[Color charge]]
* [[Partial charge]]
 
==References==
 
==External links==
* [https://web.archive.org/web/20131005012550/http://www.ce-mag.com/archive/2000/marapril/mrstatic.html How fast does a charge decay?]
 
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