Editing Van de Graaff generator (section)

=== Background ===
The concept of an electrostatic generator in which charge is mechanically transported in small amounts into the interior of a high-voltage electrode originated with the [[Kelvin water dropper]], invented in 1867 by [[William Thomson, 1st Baron Kelvin|William Thomson]] (Lord Kelvin),<ref name="Thomson">
{{cite journal
 | last1 = Thomson
 | first1 = William
 | title = On a self-acting apparatus for multiplying and maintaining electric charges, with applications to the Voltaic Theory
 | journal = The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science
 | series = Series 4
 | volume = 34
 | issue = 231
 | pages = 391–396
 | date = November 1867
 | url = https://books.google.com/books?id=2lgwAAAAIAAJ&pg=PA391
 | access-date = September 1, 2015}}</ref> in which charged drops of water fall into a bucket with the same polarity charge, adding to the charge.<ref name="Gray">{{cite book
 | last1  = Gray
 | first1 = John
 | title  = Electrical Influence Machines
 | publisher = Whittaker and Co.
 | date   = 1890
 | location = London
 | pages  = 187–190
 | url    = https://archive.org/stream/electricalinflu00graygoog#page/n210/mode/1up
}}</ref>
In a machine of this type, the [[gravitational force]] moves the drops against the opposing electrostatic field of the bucket. Kelvin himself first suggested using a belt to carry the charge instead of water. The first electrostatic machine that used an endless belt to transport charge was constructed in 1872 by [[Augusto Righi]].<ref name="Van de Graaff" /><ref name="Gray" /> It used an [[india rubber]] belt with wire rings along its length as charge carriers, which passed into a spherical metal electrode. The charge was applied to the belt from the grounded lower roller by [[electrostatic induction]] using a charged plate. John Gray also invented a belt machine about 1890.<ref name="Gray" /> Another more complicated belt machine was invented in 1903 by Juan Burboa.<ref name="Van de Graaff" /><ref name="Burboa">[https://patents.google.com/patent/US776997 US patent no. 776997, Juan G. H. Burboa ''Static electric machine'', filed: August 13, 1903, granted: December 6, 1904]</ref> A more immediate inspiration for Van de Graaff was a generator [[W. F. G. Swann]] was developing in the 1920s in which charge was transported to an electrode by falling metal balls, thus returning to the principle of the Kelvin water dropper.<ref name="Van de Graaff" /><ref name="Swann">
{{cite journal
 | last1 = Swann | first1 = W. F. G.
 | title = A device for obtaining high potentials
 | journal = Journal of the Franklin Institute
 | volume = 205
 | pages = 828
 | date = 1928
}}</ref>