Editing Tesla coil (section)

==History==
{{Main|History of the Tesla coil}}
{{Multiple image
| total_width       = 400
| image1            = Rowland resonant transformer.jpg
| caption1          = [[Henry Augustus Rowland|Henry Rowland's]] 1889 spark-excited resonant transformer,<ref name="Thomson"/> a predecessor to the Tesla coil<ref name="Strong"/>
| image2            = Tesla drawing 1899 - Evolution of Tesla transformer.png
| caption2          = Steps in Tesla's development of the Tesla transformer around 1891: (1) Closed-core transformers used at low frequencies, (2–7) rearranging windings for lower losses, (8) removed iron core, (9) partial core, (10–11) final conical Tesla transformer, (12–13) Tesla coil circuits<ref name="Tesla1899"/><ref name="Wheeler"/><ref name="Sarkar1"/> and [[Elihu Thomson]]<ref name="Strong"/><ref name="Pierce"/><ref name="Fleming"/>
}}

Electrical oscillation and resonant air-core transformer circuits had been explored before Tesla.<ref name="Britannica1903"/><ref name="Fleming"/> [[Resonant circuit]]s using [[Leyden jar]]s were invented beginning in 1826 by [[Felix Savary]], [[Joseph Henry]], [[William Thomson, 1st Baron Kelvin|William Thomson]], and [[Oliver Lodge]].<ref name="Blanchard"/> and [[Henry Augustus Rowland|Henry Rowland]] built a resonant transformer in 1889.<ref name="Strong">{{cite book |last1=Strong |first1=Frederick Finch |title=High Frequency Currents |publisher=Rebman Co. |date=1908 |location=New York |pages=41–42 |url=https://books.google.com/books?id=2S05vCsoKbkC&q=tesla+Oudin+d%27arsonval+%22elihu+thomson%22+Rowland&pg=PA41}}</ref> [[Elihu Thomson]] invented the Tesla coil circuit independently at the same time Tesla did.<ref name="Thomson1892"/><ref name="ThomsonApril1893"/><ref name="Thomson1906"/><ref name="Thomson"/> Tesla patented his Tesla coil circuit April 25, 1891.<ref name="Denicolai1"/><ref name="US_Patent_454622"/> and first publicly demonstrated it May 20, 1891, in his lecture "''Experiments with Alternate Currents of Very High Frequency and Their Application to Methods of Artificial Illumination''" before the [[American Institute of Electrical Engineers]] at [[Columbia University|Columbia College]], New York.<ref name="Martin1"/><ref name="Tesla"/><ref name="Sarkar1"/> Although Tesla patented many similar circuits during this period, this was the first that contained all the elements of the Tesla coil: high-voltage primary transformer, capacitor, spark gap, and air core "oscillation transformer".