Editing Dielectric (section)

==Terminology==
Although the term ''[[Insulator (electricity)|insulator]]'' implies low [[Electrical resistivity and conductivity|electrical conduction]], ''dielectric'' typically means materials with a high [[polarisability]]. The latter is expressed by a number called the [[relative permittivity]]. ''Insulator'' is generally used to indicate electrical obstruction while ''dielectric'' is used to indicate the [[Energy storage|energy]] storing capacity of the material (by means of polarisation). A common example of a dielectric is the electrically insulating material between the metallic plates of a [[capacitor]]. The polarisation of the dielectric by the applied electric field increases the capacitor's surface charge for the given electric field strength.<ref name=britannica/>

The term ''[[:wikt:dielectric|dielectric]]'' was coined by [[William Whewell]] (from ''[[wiktionary:dia-|dia]]'' + ''electric'') in response to a request from [[Michael Faraday]].<ref>{{cite book|author=Daintith, J.|title=Biographical Encyclopedia of Scientists|publisher=CRC Press|year=1994|isbn=978-0-7503-0287-6|page=943}}</ref><ref>James, Frank A.J.L., editor. The Correspondence of Michael Faraday, Volume 3, 1841–1848, {{cite web|url=http://hermital.org/book/holoprt5-1.htm#F5.8|title=Letter 1798, William Whewell to Faraday, p. 442.|access-date=2012-05-18|archive-url=https://web.archive.org/web/20161223121046/http://hermital.org/book/holoprt5-1.htm#F5.8|archive-date=2016-12-23|url-status=dead}} The Institution of Electrical Engineers, London, United Kingdom, 1996. {{ISBN|0-86341-250-5}}</ref>

{{Anchor|Perfect dielectric}}A ''perfect dielectric'' is a material with zero electrical conductivity ([[cf.]] [[perfect conductor]] infinite electrical conductivity),<ref>{{cite book|url={{Google books|plainurl=yes|id=ZecSEXlJE0YC|page=21}}|title=Microwave Engineering – R. S. Rao (Prof.)|access-date=2013-11-08}}</ref> thus exhibiting only a [[Displacement current#History and interpretation|displacement current]]; therefore it stores and returns electrical energy as if it were an ideal capacitor.