electrostatic machines

Electrostatic Machines

Electrostatic machines are electromechanical devices

that produce "static electricity", or electricity atcontinuous (DC) high voltage. They were fundamentalin the early studies about electricity, started in the XVIIcentury, in the form of "friction machines", and theirdevelopment culminated at the end of the XIX centurywith the development of powerful "influence machines".Today, some specialized uses for them continue to exist,but they are mostly seen as demonstration devices in

physics laboratories, with much of their history forgotten.

I started experimenting with these machines by 1973, building a first series ofmachines. With this I learned a lot about electricity, and I still think that allpeople interested in electricity or electronics shall try these machines to get areal feel of the subject. At least, high voltage static electricity is somethingthat you can see and feel. Eventually I abandoned the subject for several years,but in 1996 I renewed my interest in this subject, started to study and buildnew machines, and set up these pages.

Below are pictures and descriptions of my old machines, of machines that Ibuilt more recently, of machines built by others, pictures from old books andpapers related to electrostatic machines and other high-voltage devices, andalso some pictures from museums. There are also extensive references,covering classical and new materials. This site is always in construction. I planto add more details about the machines depicted and historical material, assoon as I find or receive more data from interested people, build andexperiment with new machines, and have time.

Está também disponível uma seção em português.

To navigate through this site efficiently, use the "open link in a new window" function of yourbrowser to see the pictures in the links, and use its search function for searching. Recentchanges.

"Ignis ubique latet, naturam amplectitur omnem"

Electrostatic Machines http://www.coe.ufrj.br/~acmq/electrostatic.html

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Machines of Toepler, Bonetti, Voss, Bohnenberger, and Nicholson

My machines

A Wimshurst machine [1][2] that I built in 1974. Front view, back view,and with two Leyden jars. A schematic diagram, with the disksrepresented as cylinders, and a description of how the Wimshurstmachine works.A Ramsden friction machine [2], built in 1975. Small (18 cm acrylic disk),but useful to test the insulation of materials and for for starting theinfluence machines in humid days.A Lebiez machine, or simplified Voss machine [p31], in front view and inback view. Built in 1975 as a kind of Voss machine, and rebuilt in 1996 inthis form. Schematic diagram, with cylinders instead of disks for mymachine. This machine is equivalent to Lord Kelvin's "replenisher" (seebelow), with better insulation. The classic Voss machine, also known asToepler-Holtz machine, is better and is built in this way, with chargecollectors and inductor plates separated. A possible similar true Vossmachine is shown here and here.A small cylindric simplified Voss machine built in 1997, with the samestructure of the previous machine. Side view, and another view. It issimilar to a Dirod machine [10].A symmetrical 2 disks Toepler machine [4], with some modifications,built in 1997. Side view, another view. A drawing. A schematic diagram,with the disks shown as cylinders. This machine has excellentperformance, and can generate higher voltage and even more currentthan a conventional Wimshurst machine with the same disk size. In 1999,I built a larger machine. Look at the bottom of the page here for adescription.The first classic Toepler machine (1865) was built in this way [4][9], witha different interconnection and disks with two sectors only. Toeplerdescribed also a symmetrical machine (1866) that is very similar to mymachine (the picture shows a sectorless machine and a similar deviceused as voltage multiplier). schematic diagram [p39].My first sectorless Wimshurst machine, or Bonetti machine [4][5][8](ray-tracing drawing), built in 1997, with 31 cm disks. A drawing.Another view. Pictures of the actual machine, in front view, and backview. A detail of the charge collectors and neutralizers. Pictures (video


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frames) of sparks from this machine: A short spark, a long spark with aloop, and a longer one. The original Bonetti machine (1894) [31] usedseries of brushes as neutralizers instead of combs.A Holtz machine [2][4]-[7] of the first kind, that I built in 1997. Adrawing. Another view, and a schematic diagram. Pictures of the actualmachine, in front view, and back view. This machine was the first reallypowerful influence machine, invented in 1865, and was very popular,even requiring external excitation to start. An apparently complete actualmachine is here. Some additional pictures, from books by H. Pellat: AHoltz machine [6] (the fixed disk is in a wrong position), a better picture[7], a double Holtz machine [6][7], and a machine with neutralizer andfriction starter [6][7]. And another good picture [14]. This picture showsa machine with a more modern structure [22]. A multiple machine [24].Here is a picture of the Holtz machine of the second kind, that uses twocounter-rotating disks, as the Wimshurst and Bonetti machines. A drawingof a possible machine.The Leyser machine (1873) [4][19], is variation of the Holtz machinewith the output taken at positions that would be under the inductor platesin the regular machine, and the neutralizer bar where the original outputcircuit would be. This is the schematic diagram of the machine, with acylinder instead of the disk. This is a different design due to Weinhold(1887), with wood inductors and no insulating plate [19]. This diagram[19] shows how it operates. Initial plans for a machine that I have builtare here, in front view and back view. The version that actually workedwas somewhat different.A double Voss machine, or double Toepler-Holtz machine, with classicalstructure, built in 1998. A drawing, and a photo of the machine. This is agood self-exciting machine, invented in 1880. With 27 cm rotating disks,it produces sparks with up to 10 cm and more than 50 uA of short-circuitcurrent.A Bohnenberger machine (1798)[4], that I built in 1998. A drawing,and a picture of the machine. An ancient machine of the "doubler" type, itis not a powerful machine, but is very interesting. See more about"doublers" in the section about influence machines below.In June 1999 I made experiments with a bipolar Van de Graaffgenerator, (drawing) similar to the original machine, but smaller.This is a large Bonetti machine, that I started to build in December1999. The disks are old ebonite disks that come with the Radiguet &Massiot Bonetti machine that I recently restored. A drawing of it. Frontview, and back view. Another view of it, and another. Some sparks, thatmay reach 20 cm..In April 2000 I finished a Wimshurst triplex machine. (drawing). It's adouble Wimshurst machine, using the close proximity between the centraldisks to increase the output current, through greater induction and


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mutual shielding. Pictures of the machine, in front view, back view, andside view. The machine produces a high current (100 uA with the 36.5 cmdisks rotating at 16 turns per second, 4 times more than a singleWimshurst machine with the same disks). With the original design, itreached only 8-12 cm sparks, eventually reaching 14 or 15 cm on drydays, because with the rather small separation of the sectors it easilysparked through them and the neutralizer bars. With half of the sectorsremoved, it produces consistent 15 cm sparks.By the same time, I made also a working version of Bennet's doubler, acurious simple influence machine.In August 2000 I made a version of Nicholson's doubler, the firstautomatic influence machine (1788).In January 2001 I completed a double Wommelsdorf machine,following closely the original design of [p84] (1920), but with modernmaterials. Front view, and back view. A collection of parts. Partialassembly. Assembling the neutralizer. Neutralizer and other detailsassembled. Back view. The machine, almost complete. Back. The disks,and the switches. The complete machine. back view, side view, other side,and another view, with only painting missing. The machine works quitewell (13.5 cm sparks, 100 uA current) for the two 28 cm disks.In March 2001 I made a curious AC electrostatic machine, apparentlynew, that I named as "half Wimshurst machine".And by April 2001 I extended the same idea to a three-disks machine, thatI named as "unfolded Wimshurst machine".A Wehrsen machine, completed in April 2002. It is a prototype for alarge Wehrsen machine (see below), that I started to build in August2001. Some parts for it at the start of the construction. Almost complete,by March 2002. Back view. Working, it performs quite well, with 11 cmsparks and 70 µA of short-circuit current.An electrostatic linear motor, completed in January 2002.A large Wehrsen machine, first tested by August 2003. Almostcomplete by July 2003. Another view, back view. Ray-tracing picture. Justbefore the first test. First test. The machine is still without its definitiverotating disk due to construction and insulation difficulties.This is a Toepler-Dirod machine that I was building by March 2004, stillwithout spark terminals, and with terminals. It's connected as thesymmetrical Toepler machine, but uses Dirod-type disks. A drawing of thefinal machine. The machine works, but is weak.Bohnenberger's Bennet's doubler. A curious little machine that I builtin April 2004.Bohnenberger's Nicholson's doubler. A version of Nicholson's doublerwith back-and-forth movement, built in May 2004. So far not so good asthe other doublers.A rotating Bennet's doubler, with a new construction using sectored


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disks, built in 2006. Photo of the machine. Another view.Wilson's machine, the oldest influence machine with symmetricaloutput, in a reproduction made in 2007. A good and interesting machine.A Van de Graaff generator with external belt. A big machine for "hairrising" demonstrations, completed in 2007.Bennet's doubler with reciprocating levers. A new structure forBennet's doubler based on Wilson's machine, built in 2007.An "electrostatic orrery". A classical demonstration device, built inJanuary 2009. It is quite heavy, but works. This site shows some similarold devices. Video.Henley electrometers built in 2009. Classical instruments first describedin 1772. A video of them operating with an electrophorus. Videos ofexperiments with an electrophorus: 1, 2.A Wimshurst machine with insulated sectors, built in 2008-2009.This machine is highly insensitive to humidity.See also the comments about machines that I have restored, in the sectionabout influence machines below. Of special interest, the Ducretet andRoger and Radiguet and Massiot machines.Electronic version of Bennet's doubler. An electrostatic generatorsuitable for electrostatic energy harvesting.

Machines built by others

A big Wimshurst machine built by Jim Banas.A sectorless Wimshurst machine with 60 cm disks. This machine was builtby Ed Wingate. A spark from this machine. Another sectorless Wimshurstmachine, with 30 cm disks. Similar to the one described by R. A. Ford in[8]. A more recent picture. Side and base view. Neutralizers, Chargecollectors. Another view. This machine was built by J. Hardesty and EdWingate. Photos sent by Steve Cole.An old Wimshurst machine repaired by Johannes Zolk in 1996, with theoriginal broken disks replaced by LP records, with good results. Frontview, and back view. Photos sent by J. Zolk.A "shake-sphere" machine [10], built by Joachim Bolz and his students in1997. It is an influence machine using two balls in a tube, moved byshaking the tube, instead of disks. It works as my Toepler machine above.An schematic diagram of it. Photo and drawing by J. Bolz. Operation of themachine.Complete plans for a beautiful Wimshurst machine, built by J. M. S. vanGelderen in 1997. Plans for the disks, a top view, a back view, a side view,and details of the terminals and Leyden jars. Pictures from the machine,seen from the front and back sides, and from above here and here.Ricardo "Rike" built this Wimshurst machine in 1997, using LP records


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for the disks. It produces 7 cm sparks. Another view.A beautiful large Wimshurst machine (40 cm disks), built by James T.Garavuso in 1998. A frontal view, another, a side view, a back view withthe terminals in storage position, another, and a view from above. Detailsif the charge collectors, neutralizers, and secondary spark gap. Thismachine produces 12 cm sparks.A Toepler machine, built by Maximiliano Guzman, from Spain, in 1998.The disks have 27 cm of diameter. A later version used larger shields anda speed multiplier in the crank.A Wimshurst machine, built by Raymond Zaborski, from the USA, in 1999.The small intersector distance and the neutralizers at low angle result inintense current and easy self-excitation, but relatively small spark length.A big motorized Bonetti machine, built by Emery Wayman, from the USA,in 1999. The machines has disks with 61 cm of diameter, and producessparks with up to 28 cm of length. Some sparks from the machine: 1, 2, 3.The terminals balls have 7.5 cm of diameter. Mr. Wayman has built also asimilar, smaller, machine with motors driving directly the disks.A motorized 2 disks Toepler machine, built by Roger Magnuson in 1999.The disks have 20 cm of diameter. Another view. Note the small Leydenjars built in the terminal supports.A classic Wimshurst machine, built by Ronald Coleman in 1999. Detail ofthe crank, and of the charge collectors. The machine is prepared for anupgrade with larger disks.A Wommelsdorf condenser machine with double rotation, built by BertPool, following plans in a thesis written by Wommelsdorf in 1904. Anotherview. This machine is a compressed version of a multiple Wimshurstmachine, with sectors mounted between pairs of insulating rings,interconnected through the external or internal edges of the rings. Oneset of rings/sectors is held by the inner side and the other by the outerside, and both turn in opposite directions.A well built small Wimshurst machine, made by Harry Boneham, fromCanada. The support structure was machined from aluminum, with thedisks having 18.5 cm of diameter. Another view.A Wimshurst machine, built by Terry Baines, from England, in 1999. With30 cm disks, it produces sparks with 3 cm.A Wimshurst machine, built by Alex Rice, from England, in 1999. Themachine has 32 cm disks, and produces sparks with 10-11 cm of length.The spark is a double exposure. A spark from the machine. In 2000, hebuilt an improved machine.A Wimshurst machine, with 18" acrylic disks, built by John Clark, fromEngland, in 2000. It produces 3" sparks.Dan Bowlds, from Kentucky, USA, designed this original machine. A baredisk rotates behind an insulating plate, that holds four wood blockspainted with conductive ink. The lateral blocks are connected to blades


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collecting charges from the back surface of the rotating disk, and toLeyden jars made in the supports. The upper and lower blocks areinductors, and are charged from the terminal blocks through singlecorona points, also made of wood. Opposite to the inductor blocks thereare interconnected neutralizer blades. The terminals are directlyconnected to the Leyden jars in the supports. An elegant structure for asmall motorized machine (the disk has 6" of diameter) that worksessentially as the Voss machine. The machine requires an initial charge tostart, and produces sparks with 1" of length. Back view, Lateral view.A Wimshurst machine with acrylic structure made by Scott Nagel in2000. With disks with 14.5" of diameter, it produces sparks with up to 6".Another spark. Note the separated small balls in the positive terminal,and the good dimensions for the sectors in the disks. The chargecollectors, with some sharp corners, were later modified.What is probably the largest working Wimshurst machine was built byPaul Hendriksen in 2000, for a technical show by ROVC , in theNetherlands. The machine uses two glass disks with 2.15 meters ofdiameter (2 cm more than the large machine built by Wimshurst in 1884),12 mm thick. The output voltage reaches 1 MV, producing sparks of up to1 meter. It turns at up to 100 rpm, producing 10 uA of current. Theoutput voltage is too high for Leyden jars, and so two copper globes areused as distributed capacitors. Details of the driving pulleys and a curiousdischarging mechanism. A long spark, another, and more sparks.Eventually (by 2008), the machine was installed in the Technoramamuseum, in Winterthur, Switzerland. Mr. Hendriksen also build severalother machines: A large Van de Graaff generator, 2.5 meters tall, thatproduces 80 cm sparks. A sectorless Wimshurst machine with 50 cmdisks, that produces 28 cm sparks. It uses an adjustable capacitor, seenhere with its minimum, medium, and maximum capacitance, that allowscontrol of the intensity of the sparks, between a minimum and a maximum,continuously. The machine uses charge collectors at just one side, and tostart it a simple friction rod is used. A hand-cranked Van de Graaffgenerator, with an unusual toroidal terminal. A small friction machine,with a 25 cm disk, that produces 2.5 cm sparks. A curious electric clock,powered by high-voltage between the two balls below. Detail. Severalhigh-voltage demonstration devices.A big Wommelsdorf condenser machine with 10 55 cm disks was built bySerge Klein, in France, in 2000. It can produce 25 cm sparks and up to0.7 mA of current. Frontal views, from the left and right sides, a view ofthe motor that turns it, detail of the disks and inductors, and anotherview. The disks are composed of three disks glued with epoxy glue, withthe central disks separating two sets of intercalated sectors. The inductorplates are also enclosed between plastic sheets glued with epoxy glue. Itworks better with the neutralizer brushes removed, with the gap between


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the disks and the neutralizer bars making the role of the gap in theneutralizer circuit of the classic machines. The machine was laterupgraded to 12 disks, with better brush supports, in an attempt toincrease the output current. A spark from the machine. Mr. Klein has alsobuilt other machines, as a Dirod, a Wimshurst machine, a big Bonettimachine, that produces 30 cm sparks, a machine similar to a Felicimachine with disks and operating in open air, and a triplex sectorlessWimshurst machine. Another view.A nice Wimshurst machine, built by Julian Phillips, in New Zealand, in2000. With 30 cm disks, it can produce 7 cm sparks. Another spark, and adescription of it.A very simple setup was developed by Michael Foster, in Los Angeles,USA, in 2001, to produce long sparks by frictional electricity. He usednothing more than a long PVC tube, a paper towel, a very simple Leydenjar capacitor, and a special positive terminal to excite long sparks. Adescription of his procedure.a Wimshurst machine, built by Luca La Valle, in Rome, Italy. He built alsoother high-voltage devices, as a Van de Graaff generator and a Tesla coil.A curious small Wimshurst machine, designed by Fausto Gazzi, inBologna, Italy. Mr. Gazzi deals with ancient instruments, and frequentlymakes restorations, as of this 4 disks Wimshurst machine.A nice Wimshurst machine, built by Chris Kitching, from England, in2001. Top view, detail from the charge collectors, and a spark with 14.5cm produced by it. The acrylic disks have 36 cm of diameter and 4 mm ofthickness, and are mounted on nylon bosses. The balls at the spark gapsand joints are softened steel balls.This and this Bonetti machines I found at eBay. They are similar to themachine described by R. A. Ford [8]. Builders unknown.Tony J. Meijers, in the Netherlands, built this nice Wimshurst machine.With 37 cm disks, it produces 14 cm sparks. Note the driving system,without crossed cords. Front view. Back view. He built also this TriplexWimshurst machine, in 2000, that with 41 cm disks produces 24 cmsparks. It also has a curious implementation of the driving system, withthe driving axle making an angle of 10 degrees with the upper axle, so thecrossed cord that drives the central disks don't touch itself at thecrossing. Front view. Back view. Side view. Other view. Assembly of thedisks. A thick 24 cm disk at the center and disks at the outer sides impedesparking to the center of the machine. The Leyden jars also haveincreased insulation.Georges Hublart, from France, built this Wimshurst machine, motorizedand with a curious construction. Side view. With 33 cm disks, it produces16 cm sparks. Note the chains driving the disks. He has also otherhigh-voltage devices, as a Van de Graaff machine.A Wimshurst machine, with conductors insulated within PVC tubes and LP


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record disks covered by adhesive plastic foil, built by Ben Noviello, USA,in 2002. It produces 10 cm sparks.A Wimshurst machine, built by Rod Heidel, from the USA, in 2002. With20 cm disks, it produces 5 cm sparks. The frontal structure is a capacitor.A beautiful Wimshurst machine, built in cherry wood and brass by GeraldJ. Schaefer, from the USA, in 2002. The disks have 18" of diameter. Sideview, Frontal view, With two demonstration devices. An intense sparkfrom it.A symmetrical Toepler machine, built by J. Keverline, from the USA, in2002. With 30.5 cm disks, it produces sparks with up to 16 cm. The diskshave increased insulation with a material used to insulate tool handles.This resulted in voltage high enough to pierce the spark shields, that hadto have their thickness increased to 4 mm.A Wimshurst machine that was once used for demonstrations at theScience Museum, in London, England, restored in 2002 by Rob Skitmore.A large Bonetti machine, built by Karl Kehrle, in Germany, in 2003. With80 cm polystyrene disks, it produces 63 cm sparks, between a pair ofaluminim balls (8, 12 cm) at the positive terminal and a 30 cm styrofoamball covered with aluminum foil at the negative terminal. The glassLeyden jars have 720 pF each. Mr. Kehrle wrote a book [49] showingexperiments with a similar sectored machine, that with 90 cm disksproduces 47 cm sparks.A Toepler machine with 48 cm disks, built by Alain Tramasaygues, fromFrance, in 2003. This improved version, with the inductor plates mountedinside a box, worked better. This is a curious Van de Graaff generator alsobuilt by him, that can produce 30 cm sparks. This is his Van de Graaffwith external belt. He also built a Dirod machine. Another view.A sectorless Wimshurst machine, with 60 cm disks, built by Grant VincentWells, in New Zealand. It can be operated by hand or by a motor, has anelectronic startup system, and produces sparks with up to 24 cm.These two machines were built by Alan Kerley. The larger machine is aVoss machine with a 21" and 17.5" disks, and the other is a smallWimshurst machine made from CD disks.This is a Wimshurst machine made by Keith Stuart, by 2000, in NewZealand. It produces 10 cm sparks. He also restored an old machine(probably German, from around 1900) for the Auckland Museum ofTransport and Technology. Front view, back view. By the end of 2003, hemade a curious combination between a symmetrical Toepler machine anda Dirod. Side view, other side, top view, end view. With 12 cm disks, itproduces 4 cm sparks.A motorized Wimshurst machine, made by Thomas Rapp, in Munich,Germany, in 2004. Another view. The disks have 30 cm of diameter. Moreinformations and other projects can be found at the author's site.A Van de Graaff generator, made by Richard Linder, in Burlington, USA.


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The terminal is a stainless steel sphere with 45 cm of diameter. Thebottom roller is made of Nylon, and the top roller of Teflon. The belt ismade of 0.4 mm Mylar foil. Mr. Linder makes demonstrations using it atthe Burlington Science Center. For the 2004-2005 school season, he builta larger machine, with a 36" terminal. The 6" belt is made of vinylimpregnated nylon. It produces arcs with 18" to 24" to a 1.5" groundedsphere.A Wimshurst machine, built by Ricardo Triches, in Brazil, in 2004.Another view.A big Van de Graaff machine, built by Harold Pollner, in California, USA,in 2004. The terminal has 30" of diameter, the comumn is 9" PVC, the beltis made with 4" Neoprene, and the machine is powered by a 1/4 hp 1725rpm ac motor. Excitation is by rolling friction between the belt and thelower roller, that is a 4" PVC coupling mounted over a wooden core. Itproduces 22" to 27" sparks, but from the rim of the sphere opening to agrounded target electrode positioned below the sphere, (as in thepicture). Sparks from other points of the sphere reach only 6" to 7".A small Wimshurst machine, with 20 cm disks, built by Hannu Eloranta,from Espoo, Finland, in 2005.A nice Wimshurst machine, belonging to Dr. Alistair Miller, England. Themachine has 19" disks and produces 6.5" sparks. It was built by AnthonySwift, that runs a museum dedicated to Victorian science in NorthYorkshire, England.A motorized Wimshurst machine, built by Peter Bradley, in England. Spark picture. Anotherspark.A curious friction machine built as a Gramophone, by Kaj V.M. Heiden, in the Netherlands. Aspark.Several Wimshurst and Bonetti machines built by Jarrod Kinsey. Another view. He experimentedalso with Wimshurst machines with sectors made with conductive ink with excellent results.Some laser experiments powered by electrostatic machines. An interesting comparison of sparks.This is a Holtz machine completed in January 2009, with simple construction but excellentperformance, as seen on this video. Another view.A Wimshurst machine, built by Christophe Branger, in France, in 2006. Another view, andanother. Spark, another spark.A Wimshurst machine, built by Emiliano Salinas Covarrubias, from the Universidad de Sonora,Mexico. The acrylic disks have 40 cm of diameter, and the structure is made of polystyrene. Itprocuces 6 cm sparks.A big Bonetti machine, made by Hal Pollner, in the USA, in 2006. With 25" disks,it produces 11" sparks. A Van de Graaff generator is used to excite themachine. Another view.A well built Wimshurst machine, built by Leonardo Giacomelli, in Italy, in2006. All parts are made in machined metals and acrylic. Front view,charge collectors, lower pulleys, upper pulleys and insulated neutralizers,and top view. The disks have 40 cm of diameter, and it produces 16 cmsparks.


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Two Lebiez machines, one hand-cranked and other motorized, made byMilan Manchich in 2007.Two Wimshurst machines made by Brian Philips in 2007. First machine,another view. It uses a flat capacitor instead of Leyden jars. Secondmachine, another view.Several machines and other devices, built by Luiz Alberto Feijó Junior, inBrazil.A Wimshurst machine built by Vaughn P. McDowell by 1986. Back view, side view.

A set of machines, Wimshurst, Voss and Ramsden, built by Leonardo Cannone, from Italy.

A big Wimshurst machine, with 61 cm disks, built by Haywood Turner, from the USA.

Wimshurst machines and Van de Graaff generators, built by Harry McCarty, from the UK.

An electrostatic motor, built by Dan Bowlds, from the USA.

A Wimshurst machine, rebuilt by Rod Heidel in 2008. The original is described above. One of theLeyden jars exploded in a test due to glue vapors inside the PVC tube. So, take care with

ventilation on these constructions...

A Wimshurst machine, built by Carlos Alberto Vargas Alfaro, from Peru, in 2008. There are some

videos here.

A Wimshurst machine built by Kevin Acres in 2008. Side view. The machine, compared to anothermachine built by his grandfather 70 years ago. Back view. The machine has 27 cm disks, and

produces 8.5 cm sparks.

A sectorless Voss machine, built by David Hodges, in 2008. It uses combs in the charge collectors,

neutralizers, and inductor chargers.

A Wimshurst machine, built by Rosalino Trobbiani, from Italy, in 2008.

A beautiful Wimshurst machine, built by Jon Bodsworth, in England. The machine was originally built25 years ago, and recently (2008) reformed. Front view, side view. The glass disks, coated withshellac, have 22 cm of diameter. The machine produces 6 cm sparks. The structure was made withmahogany and brass, the insulators were made with polyester resin, and the sectors were cut fromaluminum litho plates.

A Voss machine, restored by Alan Recce in 2009.A Wimshurst machine with classical look, built by Doug, in 2010.A Wimshurst machine, also with classical look, built by Leonard Solomon,in 2010. Another view.A powerful Bonetti machine, built by Günter Pecher, in Germany, in2010. With 60 cm disks, it produces 40 cm sparks. Another view. He builtalso this Van de Graaff generator, with a 70 cm terminal, that produces60 cm sparks.A great collection of electrostatic machines, belonging to Jaap Slikker, inthe Netherlands.A sectorless Wimshurst machine built by PV Scientific Instruments, beingused by a company in the US for tests of sensitivity of communicationequipments to static electricity, after some modifications to reduceleakage. The machine is used with this ion emitter. A photo of the machinein the dark, showing corona covering the positive side of the disks.

Friction machines


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The first electrostatic machine [15], was built by Otto von Guericke [16]by 1663, using a sulphur globe frictioned by hand. The globe could beremoved and used as source for experiments with electricity. A picture ofa working replica of the machine, from the University of Oldenburg.Another important early researcher was Francis Hauksbee, that builtseveral machines using glass globes [50][53] and cylinders by 1705.The friction machines were gradually improved through the works ofmany researchers. This is the machine with a glass globe of the abbotNollet (~1740) [7]. Eventually, the machines took a stable form, withleather friction pads (Winkler, 1744), glass globes (Bose, 1751), andinsulated charge collectors. Demonstrations with these machines werecommon.Watson's machine [51][52] (1746) had a large wheel turning several glassglobes. The prime conductors were a sword and a gun barrel suspendedfrom silk cords. Watson made many experiments with the Leyden jar, thenrecently invented.A Ramsden electrostatic friction machine [2]. Another picture [7], another[12], a good drawing [17], and a picture of a large machine [14]. The firstpopular machine using a disk (1766). Designed by J. Ramsden, aninstrumentist that also designed many other good instruments in the1700's. A beautiful restored Ramsden machine, found at eBay in 1999.Photos by Fausto Gazzi. This large machine I found in a museum inGeneva, Switzerland. A simpler machine built by myself is shown in thefirst section of this page.The machine of Le Roy (1772) [50][p26] was suitable for the production oflong sparks, due to the high insulation between the friction pads and thecharge collectors (see a more modern version as the Winter machine,below).This large disk machine (1785) with 1.6 m disks can be seen at the Muséedu Conservatoire Nacional des Arts et Metiers, In Paris, France. On itsbase is written the motto at the top of this page. There is a picture of it in[21].A brass model of a Ramsden machine. A curious decorative object,possibly from the 1930's or before. The disk has 3.5" of diameter. Photossent by Blake Awbrey.A Nairne electrostatic friction machine [7], built in 1770, consists in aglass cylinder, a friction pad in one side, and a charge collector in theother, both connected to insulated conductors. Another one. The machinewas used for medical purposes.The van Marum electrostatic friction machine (1784) [9]. By moving thetwo curved bars with charge collectors, it was possible to collect chargefrom the disk (bars as shown), or from the friction pads (bars turned 90degrees), producing voltage with any polarity, as shown here. Van Marumis also known for the big machine [16][21] that he had made in 1784, that


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is now in the Teylers museum.A similar machine, now in the Deutsches Museum, Munich, Germany,belonged to Georg Ohm (1830?)[21]. Another view. Photos sent by HansBussmann (I could not find it there in september 2008).A belt machine [50] built by N. Rouland by 1785, had a charge collectorwith blades that collect charges from a silk belt rubbed by two groundedtubes covered with hare fur [21].An old friction machine using a glass disk. Another picture of the samemachine. Photos sent by Don Day.A Winter electrostatic friction machine. One of the most efficient frictionmachines. A picture from an old book [3], and another, from H. Pellat [7].This was the last popular structure for friction machines, as shown inthese catalog pictures from the 1920's: this and this are from [17], andthis is from [22]. The characteristics of the machine are the disk frictionedat one side, at both faces, with a pair of charge collectors at the otherside, shaped as rings with points turned to the disks. Sometimes a largewood ring (Winter's ring) with a metallic core was attached to theterminal, increasing its capacitance. A double adjustable version can beseen on the first picture.The Woodward machine (1840) [43][21] was a modified Ramsdenmachine, with the prime conductor located above the disk, or disks,saving some space. It could also generate negative voltage, by mountingthe upper friction pad in place of one of the charge collectors. This doublemachine is in the University of Porto, Portugal. Partially disassembled.Pictures by Marisa Monteiro.The Armstrong hydroelectric machine [2], a friction machine using steamas charge carrier (1840). It is just an insulated boiler producing a steamjet mixed with water droplets. A better picture is here [9]. Very powerfulmachines of this kind were built for research.The Lorente generator. A triboelectric machine composed of fourcylinders that roll together without friction, under a slight pressure. Thetwo outermost cylinders are metallic, and the two central cylinders are ofdistinct insulating materials (nylon and teflon). Opposite charges arecollected in the metallic cylinders. The basic machine produces voltagesof some tens of kV, but several modules can be stacked for more voltage. Acoaxial version is also possible. Pictures from actual models are here andhere. This device was invented and patented by G. Lorente, who sent thepictures.Rolling friction is also commonly used in models of the Van de Graaffgenerator, although the principle of the charge generation system onthose machines is a mix of friction and influence.

Influence machines


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The first rotating influence machines were the "doublers". The first wasNicholson's doubler [p14] (1788). It was a rotating implementation ofBennet's doubler (1787), a device based on Volta's "electrophorus"(1775) [p110], that allowed great multiplication of a small initial chargeby a series of repeated operations with three insulated plates. The originalmachine proposed by Nicholson didn't require a connection to ground,but versions with explicit ground connections are also possible, as this[28], and this (built by Wimshurst) [p14]. An actual machine exists theMusee d'histoire des sciences, in Geneva (the site has a movie of thedoubler in operation), that looks as this machine (John Read's doubler)[p106]. See my Nicholson's doubler. A similar implementation, wherethe two plates that are fixed in Nicholson's device rotate, isBohnenberger's machine (1798) [4]. Bohnenberger designed severalother doublers, as this automated version of Bennet's doubler andthis variation of Nicholson's doubler (1801) [p107], both operatingwith back and forth movements. See my Bohnenberger's machine.Multipliers based on a different system are also possible, as Péclet'scondenser (1841) that increases the charges linearly with the number ofoperations [p87] and a multiplier with 4 plates invented by Pfaff andSvanberg that combines addition and multiplication [54]. Multipliersdirectly based on the electrophorus were studied, by Volta himself [p110]and Lichtenberg.A similar adding device was Cavallo's multiplier (1795), where a movableinsulated plate was moved back and forth, alternatively being groundedunder the influence of a second previously charged plate, and touching athird insulated plate close to a grounded fourth plate. After some cycles,the grounded plate would be removed, causing the accumulated charge atthe third plate to rise its potential to about the potential of the secondplate times the number of cycles [4].Two Cavallo multipliers can be combined in Wilson's machine (1804), acurious machine that incorporates essentially the same idea of thesymmetrical rotating machines developed much later.One of the scientists that studied doublers was Erasmus Darwin. His"commonplace book" contains a sketch of a doubler, that appears also in[p14], that is probably the first drawing of these devices. His book"Phytologia" contains a drawing of a "pendulum doubler", attributed toBennet (see here).The next development was of symmetrical influence machines, usinginfluence to generate new charges and Faraday's shielding effect tocollect them. The first was Belli's machine [4][p14] (1831), the firstsymmetrical influence machine. A picture of an elaborated actualmachine. Belli developed also a different machine using the sameprinciple, shown here. The same basic structure appears in Lord Kelvin's"replenisher" [2][p92] (1867), in schematic representation, and as


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constructed [12]. A simple machine built with insulated curved metalplates, used as part of measurement instruments. Here is a ray-tracingpicture similar to a machine that I built by 1973. The rotation of thecentral insulating bar with two metallic carriers, touching the fourcontacts, causes accumulation of opposite charges in the outer plates.Another similar machine was the Varley machine [26] (1860).A device that can be considered an influence machine is Einstein's"Maschinchen" (little machine). It was a mechanical voltage multiplierresembling a multistage Belli machine without feedback. This paperdescribes it.A curious machine [18] that appears to be similar to Belli's machine, if thelateral brushes are connected to the fixed plates. The same machineappears illustrating this advertisement (1962) but with an added set ofbrushes installed, to separate the output circuit from the inductor plates,as in the Voss machine.The Piche machine, or Bertsch machine (1866) [7]. One of the simplestinfluence machines, uses an insulator plate (I), that is separatelyelectrized by friction, and used to generate charges in the rotating diskby induction. See the original letters about this machine in thereferences. A similar device is the Dubrowski machine [22]. This type ofmachine was called "continuous electrophorus".The Carré machine [6] (1868). A friction machine below charges byinduction a fast rotating disk, that transfers charge to the upperconductor. It is similar in operation to the Bertsch machine, butregenerates the charge in the inductor. A better picture [7]. A variation[14] with slanted combs. A ray-tracing drawing. A photo from an actualmachine, sent by John Newman. A machine with a double terminal. TheVan de Graaff generator [p4][8] is an evolution of this machine, with abelt instead of the disk, and a more efficient charge collector at the top.This machine is in a museum in Switzerland. Another machine, in aMuseum in Spain.A double Bonetti machine from the same museum, with curiously shapedneutralizer combs (?).Another antecessor of the Van de Graaff generator is Righi's electrometer[p55] (1872), that used a rubber string with brass rings for chargetransport, and a hollow sphere as charge collector. A picture of thismachine [41]. Similar machines are also discussed in [p59] (1875), as abipolar machine, that must have grounded pulleys, and another, that addsa neutralizer circuit and can use insulated pulleys.Righi studied also a belt machine [p59], that antecipates a regenerativecharging system used in some Van de Graaff machines, and shows acurious polarity reversal phenomenon, where for some time the beltoperates with bands of both polarities.Righi designed this big Holtz machine [41] (~1875), used at the Regio


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Istituto Tecnico de Bologna for teaching and research. A drawing of asimilar machine [42].A Lord Kelvin's water machine (1867) [1][p91]. It is an influence machinethat uses water droplets instead of rotating carriers. It works in the sameway of the 2 disks Toepler machine. Another picture [6] of a similarmachine. An improvement of this machine using two additional units foroutput, avoiding the discharge of the inductors, was proposed by Fuller in1888 [p103] [ p62]. A different version was proposed by SylvanusThompson in 1887 [p104].The Schwedoff influence machine [9][13][29] (1868). A very strangemachine. The lower plates form a modified Holtz machine, with inductorplates replaced by combs (dotted lines) charging the lower surface of thelowest fixed disk with charge taken from the charge collectors. This firstmachine provides bias for the sectors in the lower plate of the upperassembly (the even-numbered ones with one polarity, the others withanother), that form a current multiplier. The output is taken between thetwo insulated sets of combs over the upper, rotating disk. This picturefrom the original paper [p46] shows more clearly the connections. This isthe charge collector [p46] that completes the machine.A Toepler-Holtz machine, or Voss machine with classical design. From acatalog from the 1920's. Two more pictures here and here. Pictures foundin the Gemmary's forum.Several Toepler-Holtz, or Voss, machines from [17]: A simple machine,another, a double machine, a quadruple machine (see one here), and amultiple machine. Two more simple machines from [18]: this and this. Andanother one, from [22].A magnific quadruple Voss machine, at the museum of the University ofPavia, Italy.A Holtz-Wimshurst machine [4][23], simple and with a frictional starter[4][23]. These were Holtz-type machines with several disks and improvedconstruction, as the inductors fixed in separate square glass plates,developed by Wimshurst by 1878.The Kundt machine [4] (1868) was a mixed friction-influence machine,similar to a Bertsch machine with the back side of the disk frictioned by afriction pad with a silk flap attached, as in a friction machine. At the frontside are positioned two charge collectors, as in the Bertsch machine. Asimilar machine was the Cantoni machine (1869), that added a thirdcharge collector at the back side of the disk, so the machine can also beused as a friction machine.A good picture of a classic Wimshurst machine (1883) [1]. A Line drawingof the same picture [2].A Wimshurst machine [6], similar to one that exists in the Museum of theUFRJ Engineering School, and that I restored. Another [14] similarmachine. That machine was built by F. Ducretet and E. Roger, Paris, and


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originally should look as in this (front) and this (back) ray-tracingdrawings. Here are comments about the restoration and morepictures. This is how it is now, compared with my 1974 Wimshurst. Alarge spark produced by the machine in a demonstration. Anotherpicture, showing two of these machines connected as a generator andmotor pair [24]. These pictures [23] show discharge images onphotographic plates obtained with one of these machines. A positivedischarge, and a negative discharge. A multiple machine from the sameinstrument builder, at the University of Porto, Portugal.Here is another Wimshurst machine from the same museum that I restored(ray-tracing), a picture of it, and some comments about the restoration.The largest Wimshurst machine ever built is presently at the Science andIndustry Museum in Chicago, USA. It was built in England in 1885, with7 foot glass disks 3/8 inch thick, and produced sparks with 22 inches. Thispicture is from Engineering, Vol. 39, 1885, scanned from [23] (alsoappears in [4][5][8][26]). More informations and pictures about thismachine.More Wimshurst machines, from [14]: A large simple machine, a doublemachine, a quadruple machine, and an octuple machine. And also twomachines from [15], with ebonite disks and Leyden jars with two sections,and with glass disks. Two more large machines from [22]: A simplemachine and a quadruple machine.Wimshurst machines, from the collection belonging to Louie Scribner: AFrench machine (Bonetti), and a German machine (Leybold, 1901).Wimshurst machines that have full construction details in [4][23]: Alaboratory machine, a long spark machine, and a twelve plates machine.Designs by J. Wimshurst.A "Voltana" Wimshurst machine [34](1921), used to run an electrostaticmotor, and a bank of Geissler tubes. A larger machine, a smaller machine,another machine, more Geissler tubes being lighted, lighting a spinningGeissler tube, charging a Leyden jar, and charging a spring, that expandswhen charged [35].Several machines, from [38], that illustrate the state of the art by 1900: Aclassic Wimshurst machine made by Bonetti, with Leyden jars thatsupport the terminals, a complex double machine and a large multiplemachine made by Ducretet, and a machine with large conductors, that actas capacitors. The classic Bonetti sectorless machine, a multiple Bonettimachine, and a double Bonetti machine.Some multiple Wimshurst machines: A double machine, built by theinstrument builder E. Balzarini, similar to the machines that appear in its1907 catalog. Note the triple brushes at the neutralizers. A quadruple

machine, built by Newton & Co. Back view. Detail from one of the chargecollector assemblies. Pictures from eBay auctions.


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Wimshurst machines with an orthogonal drive system were built bycompanies as Central Scientific Co. A machine with the Leyden jarsserving as terminal supports. A small unusual German machine. A largermachine, and a big machine . One of the pulleys below is driven by the

crank. The other runs freely 1.A Wimshurst machine with cast iron structure, including the neutralizers1.The Wimshurst machine can also be built with cylinders instead of disks[4][23]. A more practical structure was designed by Lemström [5][8](1899), with the two cylinders turning around a fixed central axle, thatalso holds the internal charge collectors and neutralizers. The axle wasseparated in two sections by an insulating block at the center. Themachine was kept warm, dry, and ventilated by a heating system and thesides of the cylinders, shaped as fans. See his patents.The Wimshurst alternating machine (1891), that generates alternatingvoltage, synchronized with the rotation, with a polarity reversal at each3/4 of rotation of the disk. The operation of this machine was considereddifficult to explain [5]. A single disk with sectors at both sides,alternating, rotates between two pairs of collectors/inductors. Picturefrom Engineering.A triple Bonetti machine [11]. This kind of multiple machine was used inearly X-ray work.By June-October 1999 I restored a similar quadruple Bonetti machine,built by Radiguet & Massiot (~1910), for my university's museum. Somepictures of the machine during initial tests and a report about therestoration are available.Another double Bonetti machine [26], with similar features.A cylindric Bonetti machine [11]. A compact design with high currentoutput. This appears to be a large machine built by Bonetti by 1894,where the cylinders had 50 cm of diameter and height [p78]. Anothercylindric machine [26].A machine that appears to be a sectored Holtz machine [22], said to bequite powerful. There are fixed inductors on the back plate, that arecharged by sectors at the back of the rotating disk through brushes thatproject through two holes in the fixed disk.A motorized Voss machine with a fully sectored rotating disk [26].P. V. Schaffers (1885) [4][5][p29][p32] described a machine that isessentially a Wimshurst machine with the charge collectors at differentpositions, with brushes at the charge collectors. The Schaffers machineworks as a combination of the Wimshurst machine and the Holtz machineof the second kind, producing higher current (schematic). A (bad) pictureof a Schaffers machine [26].A Wehrsen machine [1][26][27][32][34][p77] (1907). Wommelsdorf's


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idea, it is a highly insulated sectored Holtz-style machine with sectorsembedded in the rotating disk, contacted through small buttons, andinductors [34] also totally insulated behind celulloid plates. Somemachines had corrugated sectors for greater surface area, what increasesthe output current [5], or mounted at different planes for higherinsulation [26]. They had switches to allow the direct connection betweenthe inductors and the output circuit, for startup as a "replenisher"machine [32]. Two better pictures from [17]: A large machine, and a smallmachine. A simple machine, and a large machine, from [22]. A machinewith direct motor drive [26]. A similar machine [p77]. Wehrsen's"Mercedes" machine [34][26], with one rotating disk, and with tworotating disks, one at each side of the fixed disk. A similar machine, builtin 1911, exists in the Cavendish Laboratories, England. left view, rightview, back view. Detail from the switches, and from the central inductorplates. The machine is normally under an enclosure, and wasdisassembled for cleaning and investigation of why it doesn't workanymore in 1999. Photos sent by Tacye Phillipson.The Wommelsdorf condenser machine [1][17][18][p84] (1902-1920) wasthe last of the classical disk machines. It was basically a sectoredVoss-style machine with double induction plates, one pair at each side ofthe rotating disk, and with all the sectors and inductor plates enclosed inebonite plates. Some models had a switch in the middle of the neutralizerbar. A simpler model [17]. In the last versions, the disk had a full set ofembedded sectors, monted in alternate groups separated by one or twothin insulating disks. The sectors were touched only at the borders of thedisk by brushes running in a V groove there. The ebonite disk wascovered by a material (celluloid or bakelite) resistent to deteriorationcaused by ozone and other gases produced by electrical discharges.[5][8]. Schematic diagram [27]. Versions with multiple sections were alsobuilt, with some versions combining different charging systems for theinductors, with alternate sections charging the inductors from brushes atthe edge of the disks and others from brushes touching the sides of thedisks, as in a Holtz machine. Another version [22] with older design,totally enclosed and with fixed contacts for the neutralizer. Partialschematic diagram. A similar machine [p80], another, an open machine,and a very large machine [p81][46] along with a small machine. Acondenser machine powered by a steam engine [46]. Wommelsdorfdesigned also machines with pairs of disks rotating in opposite directions[45][p83], similar to multiple Wimshurst machines, as this [46], a triplexWimshurst machine with a central disk accessed through the edge.Several of the papers and patents by Wommelsdorf are available here. Seealso my Wommelsdorf machine.See some tables with the performances of several machines.The Pidgeon machine [26] was a Wimshurst machine with fixed inductors


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positioned in a way that increases the induction effect. Fixed inductorswith same polarity of the opposite disk were placed surrounding,insulated, each neutralizer brush. The sectors were embedded in the disks[5][26][p53][p54][p111]. Pidgeon studied also machines based on"triplex Wimshurst" sections (double machines with a single centraldisk), with enclosed sectors, that produce more current. The first Pidgeonmachine had a quite strange structure [p111], and the disks had slantedsectors for more uniform induction.Piggott made a set of experiments with radiotelegraphy and "antigravity"using a compact double Wimshurst machine enclosed in a pressurizedbox. Drawings from his patent (1911) showing the machine. Front view,side view, top view.A "Dirod" generator. A modern electrostatic machine, designed by A. D.Moore [10]. It is a cylindric machine similar to the Belli machine, or LordKelvin's replenisher, with metal rods as carriers. The output is taken atthe inductors.Another machine described in A. D. Moore's book [10] is the "shake-sphere" machine. It is electrically equivalent to the symmetricalToepler machine or the earlier Wilson's machine.From the 1940's to the 1960's, Nöel J. Felici, in France, developed aseries of high-power electrostatic generators [40], initially for applicationsin research. This site, by Lyonel Baum, contains many informations abouthis work.See also the several machines that I have built, in the section "mymachines", above. The linked pages have many informations about themachines.

Other high-voltage devices, not electrostatic

Changing of subject, an Induction coil [1], or Ruhmkorff coil (1851). A"fly-back" circuit with a mechanical interruptor, that eventually replacedthe electrostatic machines as a practical source of high voltage. Itsschematic diagram [1], ommiting the secondary of the transformer, that iswound with many turns of thin wire and well insulated. By 1867Ruhmkorff (instrument maker in France) was making coils that couldproduce sparks with 40 cm. A spark image (16 cm) obtained with one ofthese machines, with the terminals applied to a photographic plate [12].The positive terminal was in the left.The Planté rheostatic machine. It produces high voltage by charging abank of capacitors in parallel and discharging them in series. Theconnections are made by contacts in the rotating cylinder [24][47]. Theinput is obtained from a battery.A resonance excitator [1], with adjustable inductances (L1, L2), Leyden


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jar capacitors (C1, C2), and a spark gap, used in old experiments aboutresonance.Self-resonant coils [1] with different lengths, that emit corona dischargeswhen driven at their resonant frequencies by the excitator above.Connection between an induction coil (J), the excitator, and the resonantcoils (Seibt experiment) [1]. By changing the excitator inductance, it ispossible to put one or another of the self-resonant coils in resonance. Thisexperiment is a variation of the "Tesla coil" circuit, using a directconnection instead of a transformer. See my implementation of a similarsystem, and follow the links to see my other experiments with multipleresonance networks.Complete apparatus for the Seibt experiment [18]. A variation using alarge open primary coil [17]. A curious experiment using a Tesla coil anda long resonator coil, where corona to two wires demonstrates standingwaves.A classic Tesla transformer [1]. A primary coil with a few turns of heavywire (or tubing), and a well-insulated secondary with many turns. Itproduces a similar result if the primary is inserted in series with the sparkgap in the excitator above. Several Tesla coils, from [18].Apparatus for Tesla experiments, with an usual Tesla transformer, andwith an oil-insulated transformer [18]. A large Leyden jar capacitor isconnected in series with a spark gap and the primary of the transformer.The capacitor is charged by an induction coil, or a powerful influencemachine. The other devices shown are for demonstrations of the effects ofhigh-frequency high voltage. Similar apparatus with the usualair-insulated transformer [17], and an experiment to demonstrate the highimpedance of a wire loop, using a Tesla coil with the primary coil insidethe secondary [22].An Oudin coil (1898) [33], a Tesla coil with the primary and secondarywindings forming an autotransformer. Another Oudin coil [36]. See alsomy Tesla coil, that can also be operated as an Oudin coil.

Half Wimshurst, Toepler, Wommelsdorf, Holtz, and Unfolded Wimshurst machines

Some final observations, about pseudo-science, safety measures, andtroubleshooting.Calculating the output current of electrostatic machines.References - Books, papers and patents about electrostatic machines,


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cited between "[]" in the text.See also my links about these subjects.Community in Orkut.Links to e-mail addresses or collaborators had the "@" replaced by "|".

1 Found in the catalogs here.

Last update: 19 May 2010. Recent changes and updates© 1996-2010 Antonio Carlos M. de QueirozThe contents of these pages cannot be reproduced without consent of the author.

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