Editing Electromagnet (section)

== History ==
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| image1   = Sturgeon electromagnet.png
| caption1 = Sturgeon's electromagnet, 1824
| width1   = 150
| image2   = Joseph Henry electromagnet.png
| caption2 = One of Henry's electromagnets that could lift hundreds of pounds, 1830s
| width2   = 163
| image3   = Joseph Henry electromagnet closeup.jpg
| caption3 = Closeup of a large Henry electromagnet
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Danish scientist [[Hans Christian Ørsted]] discovered in 1820 that electric currents create magnetic fields. In the same year, the French scientist [[André-Marie Ampère]] showed that iron can be magnetized by inserting it into an electrically fed [[solenoid]].

British scientist [[William Sturgeon]] invented the electromagnet in 1824.<ref>{{cite journal
  | last = Sturgeon
  | first = W.
  | title = Improved Electro Magnetic Apparatus
  | journal = Trans. Royal Society of Arts, Manufactures, & Commerce
  | volume = 43
  | pages = 37–52
  | year = 1825
  }} cited in {{cite book
 |last        = Miller
 |first       = T.J.E
 |title       = Electronic Control of Switched Reluctance Machines
 |publisher   = Newnes
 |year        = 2001
 |pages       = 7
 |url         = https://books.google.com/books?id=E8VroIWyjB8C&pg=PA7
 |isbn        = 978-0-7506-5073-1
 |url-status   = live
 |archive-url  = https://web.archive.org/web/20161203032419/https://books.google.com/books?id=E8VroIWyjB8C&pg=PA7
 |archive-date = 2016-12-03
}}</ref><ref>Windelspecht, Michael. [https://books.google.com/books?id=hX1jPbJVSu4C&dq=%22William+Sturgeon%22+electromagnet+1825&pg=PR22 Groundbreaking Scientific Experiments, Inventions, and Discoveries of the 19th Century] {{webarchive|url=https://web.archive.org/web/20170111015300/https://books.google.com/books?id=hX1jPbJVSu4C&pg=PR22&lpg=PR22&dq=%22William+Sturgeon%22+electromagnet+1825&source=web&ots=BhXj3j9j4t&sig=6gI6QNC-Yc5YMCY5RpEE43eIfgU&hl=en&sa=X&oi=book_result&resnum=9&ct=result |date=2017-01-11 }}, xxii, Greenwood Publishing Group, 2003, {{ISBN|0-313-31969-3}}.</ref> His first electromagnet was a horseshoe-shaped piece of iron that was wrapped with about 18 turns of bare copper wire. ([[Insulator (electricity)|Insulated]] wire did not then exist.) The iron was [[varnish]]ed to insulate it from the windings. When a current was passed through the coil, the iron became magnetized and attracted other pieces of iron; when the current was stopped, it lost magnetization. Sturgeon displayed its power by showing that although it only weighed seven ounces (roughly 200 grams), it could lift nine pounds (roughly 4 kilos) when the current of a single-cell power supply was applied. However, Sturgeon's magnets were weak because the uninsulated wire he used could only be wrapped in a single spaced-out layer around the core, limiting the number of turns.

Beginning in 1830, US scientist [[Joseph Henry]] systematically improved and popularised the electromagnet.<ref name="Cavicchi">{{cite web
 |last        = Cavicchi
 |first       = Elizabeth
 |title       = Series and Parallel Experimenting with Electromagnets
 |publisher   = Pavia Project Physics, Univ. of Pavia, Italy
 |url         = http://ppp.unipv.it/Collana/Pages/Libri/Saggi/Volta%20and%20the%20History%20of%20Electricity/V%26H%20Sect4/V%26H%20387-407.pdf
 |access-date = August 22, 2015
 |url-status  = live
 |archive-url = https://web.archive.org/web/20160315231307/http://ppp.unipv.it/Collana/Pages/Libri/Saggi/Volta%20and%20the%20History%20of%20Electricity/V%26H%20Sect4/V%26H%20387-407.pdf
 |archive-date = March 15, 2016
}}</ref><ref name="Sherman">{{cite web
 |last        = Sherman
 |first       = Roger
 |title       = Joseph Henry's contributions to the electromagnet and the electric motor
 |website     = The Joseph Henry Papers
 |publisher   = The Smithsonian Institution
 |year        = 2007
 |url         = http://siarchives.si.edu/history/exhibits/henry/electromagnetism
 |access-date = 2008-08-27
 |url-status  = live
 |archive-url = https://web.archive.org/web/20120608070442/http://siarchives.si.edu/history/exhibits/henry/electromagnetism
 |archive-date = 2012-06-08
}}</ref> By using wire insulated by silk thread and inspired by [[Johann Schweigger|Schweigger's]] use of multiple turns of wire to make a [[galvanometer]],<ref>{{cite web|title=Schweigger Multiplier – 1820|url=https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/museum/schweigger-multiplier|website=Maglab|publisher=National High Magnetic Field Laboratory|access-date=17 October 2017|url-status=live|archive-url=https://web.archive.org/web/20171017202030/https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/museum/schweigger-multiplier|archive-date=17 October 2017}}</ref> he was able to wind multiple layers of wire onto cores, creating powerful magnets with thousands of turns of wire, including one that could support {{convert|2063|lb|kg|abbr=on}}. The first major use for electromagnets was in [[telegraph sounder]]s.

The [[magnetic domain]] theory of how ferromagnetic cores work was first proposed in 1906 by French physicist [[Pierre-Ernest Weiss]], and the detailed modern quantum mechanical theory of ferromagnetism was worked out in the 1920s by [[Werner Heisenberg]], [[Lev Landau]], [[Felix Bloch]], and others.