Electrostatic generator

Electrostatic generator

Overview

An electrostatic generator, or electrostatic machine, is a mechanical device that produces static electricity
Static electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...

, or electricity at high voltage
High voltage
The term high voltage characterizes electrical circuits in which the voltage used is the cause of particular safety concerns and insulation requirements...

 and low continuous current. The knowledge of static electricity dates back to the earliest civilizations, but for millennia it remained merely an interesting and mystifying phenomenon
Phenomenon
A phenomenon , plural phenomena, is any observable occurrence. Phenomena are often, but not always, understood as 'appearances' or 'experiences'...

, without a theory to explain its behavior and often confused with magnetism. By the end of the 17th Century, researchers had developed practical means of generating electricity by friction, but the development of electrostatic machines did not begin in earnest until the 18th century, when they became fundamental instruments in the studies about the new science of electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

.
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Encyclopedia

An electrostatic generator, or electrostatic machine, is a mechanical device that produces static electricity
Static electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...

, or electricity at high voltage
High voltage
The term high voltage characterizes electrical circuits in which the voltage used is the cause of particular safety concerns and insulation requirements...

 and low continuous current. The knowledge of static electricity dates back to the earliest civilizations, but for millennia it remained merely an interesting and mystifying phenomenon
Phenomenon
A phenomenon , plural phenomena, is any observable occurrence. Phenomena are often, but not always, understood as 'appearances' or 'experiences'...

, without a theory to explain its behavior and often confused with magnetism. By the end of the 17th Century, researchers had developed practical means of generating electricity by friction, but the development of electrostatic machines did not begin in earnest until the 18th century, when they became fundamental instruments in the studies about the new science of electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

. Electrostatic generators operate by using manual (or other) power to transform mechanical work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

 into electric energy. They develop electrostatic charges of opposite signs rendered to two conductors, using only electric forces. They work by using moving plates, drums, or belts to carry electric charge to a high potential
Electric potential
In classical electromagnetism, the electric potential at a point within a defined space is equal to the electric potential energy at that location divided by the charge there...

 electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...

. The charge is generated by one of two methods: either the triboelectric effect
Triboelectric effect
The triboelectric effect is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated...

 (friction) or electrostatic induction
Electrostatic induction
Electrostatic induction is a redistribution of electrical charge in an object, caused by the influence of nearby charges. Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762. Electrostatic generators, such as the Wimshurst machine, the...

.

Description


Electrostatic machines are typically used in science classrooms to safely demonstrate electrical forces and high voltage phenomena. The elevated potential differences achieved have been also used for a variety of practical applications, such as operating X-ray tubes, medical applications, sterilization of food, and nuclear physics experiments. Electrostatic generators such as the Van de Graaff generator
Van de Graaff generator
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate very high voltages on a hollow metal globe on the top of the stand. It was invented in 1929 by American physicist Robert J. Van de Graaff. The potential differences achieved in modern Van de Graaff...

, and variations as the Pelletron
Pelletron
A pelletron is a type of electrostatic particle accelerator similar to a Van de Graaff generator. Pelletrons have been built in many sizes, from small units producing voltages up to 500 kilovolts and beam energies up to 1 megaelectronvolt of kinetic energy, to the largest system, which has...

, also find use in physics research.

Electrostatic generators can be divided into two categories depending on how the charge is generated:
  • Friction machines use the triboelectric effect
    Triboelectric effect
    The triboelectric effect is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated...

     (electricity generated by contact or friction)
  • Influence machines use electrostatic induction
    Electrostatic induction
    Electrostatic induction is a redistribution of electrical charge in an object, caused by the influence of nearby charges. Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762. Electrostatic generators, such as the Wimshurst machine, the...


History


The first electrostatic generators are called friction machines because of the friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 in the generation process. A primitive form of frictional electrical machine was invented around 1663 by Otto von Guericke
Otto von Guericke
Otto von Guericke was a German scientist, inventor, and politician...

, using a sulphur globe that could be rotated and rubbed by hand. It may not actually have been rotated during use, but inspired many later machines that used rotating globes. Isaac Newton
Isaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...

 suggested the use of a glass globe instead of a sulphur one. Francis Hauksbee
Francis Hauksbee
Francis Hauksbee the elder , also known as Francis Hawksbee, was an 18th-century English scientist, and a Fellow of the Royal Society...

 improved the basic design, his machine enabling a glass sphere to be rotated rapidly against a woollen cloth.

Generators were further advanced when Prof. Georg Matthias Bose of Wittenberg added a collecting conductor (an insulated tube or cylinder supported on silk strings). Boze was the first to employ the "prime conductor" in such machines, this consisting of an iron rod held in the hand of a person whose body was insulated by standing on a block of resin.

In 1746, Watson's machine had a large wheel turning several glass globes with a sword and a gun barrel suspended from silk cords for its prime conductors. J. H. Winkler, professor of physics at Leipzig
Leipzig
Leipzig Leipzig has always been a trade city, situated during the time of the Holy Roman Empire at the intersection of the Via Regia and Via Imperii, two important trade routes. At one time, Leipzig was one of the major European centres of learning and culture in fields such as music and publishing...

, substituted a leather cushion for the hand. Andreas Gordon of Erfurt, a Scottish Benedictine monk, used a glass cylinder in place of a sphere. Jesse Ramsden
Jesse Ramsden
Jesse Ramsden FRSE was an English astronomical and scientific instrument maker.Ramsden was born at Salterhebble, Halifax, West Riding of Yorkshire, England. After serving his apprenticeship with a cloth-worker in Halifax, he went in 1755 to London, where in 1758 he was apprenticed to a...

, in 1768, constructed a widely used version of a plate electrical generator. By 1784, the van Marum machine could produce voltage with either polarity. Martin van Marum
Martin van Marum
Martin van Marum was a Dutch scientist and teacher, who studied medicine and philosophy in Groningen...

 constructed a large electrostatic machine of high quality for his experiments (currently on display at the Teylers Museum
Teylers Museum
Teyler's Museum , located in Haarlem, is the oldest museum in the Netherlands. The museum is in the former home of Pieter Teyler van der Hulst . He was a wealthy cloth merchant and Amsterdam banker of Scottish descent, who bequeathed his fortune for the advancement of religion, art and science...

 in the Netherlands).

Ingenhousz
Jan Ingenhousz
Jan Ingenhousz or Ingen-Housz FRS was a Dutch physiologist, biologist and chemist. He is best known for showing that light is essential to photosynthesis and thus having discovered photosynthesis. He also discovered that plants, like animals, have cellular respiration...

, during 1746, invented electric machines made of plate glass. Experiments with the electric machine were largely aided by the discovery of the property of a glass plate, when coated on both sides with tinfoil, of accumulating a charge of electricity when connected with a source of electromotive force. The electric machine was soon further improved by Andrew Gordon
Andrew Gordon (Benedictine)
Andrew Gordon was a Scottish Benedictine monk, physicist, and inventor. He made the first electric motor.-Life:...

, a Scotsman, Professor at Erfurt, who substituted a glass cylinder in place of a glass globe; and by Giessing of Leipzig who added a "rubber" consisting of a cushion of woollen material. The collector, consisting of a series of metal points, was added to the machine by Benjamin Wilson
Benjamin Wilson (painter)
Benjamin Wilson was an English painter, printmaker and scientist .He was the 14th child of Major Wilson, a wealthy York clothier whose house was decorated by the French history painter, Jacques Parmentier...

 about 1746, and in 1762, John Canton
John Canton
John Canton FRS was an English physicist.Canton was born in Middle Street Stroud, Gloucestershire, the son of a weaver John Canton and Esther He had only a common education, after which he was put apprentice to a broadcloth weaver, but his leisure hours were devoted to mathematical studies, and...

 of England (also the inventor of the first pith-ball electroscope) improved the efficiency of electric machines by sprinkling an amalgam of tin over the surface of the rubber.

In 1785, N. Rouland constructed a silk belted machine which rubbed two grounded hare fur covered tubes. Edward Nairne
Edward Nairne
Edward Nairne b. Sandwich, England, 1726; d. London, 1 September 1806, was an optician and scientific instrument maker. He was apprenticed to the optician Matthew Loft in 1741 and established his own business at 20 Cornhill in London after Loft's death in 1748...

 developed an electrostatic generator for medical purposes in 1787 which had the ability to generate either positive or negative electricity, the first named being collected from the prime conductor carrying the collecting points and the second from another prime conductor carrying the friction pad. The Winter machine possessed higher efficiency than earlier friction machines. In the 1830s, Georg Ohm
Georg Ohm
Georg Simon Ohm was a German physicist. As a high school teacher, Ohm began his research with the recently-invented electrochemical cell, invented by Italian Count Alessandro Volta. Using equipment of his own creation, Ohm determined that there is a direct proportionality between the potential...

 possessed a machine similar to the van Marum machine for his research (which is now at the Deutsches Museum
Deutsches Museum
The Deutsches Museum in Munich, Germany, is the world's largest museum of technology and science, with approximately 1.5 million visitors per year and about 28,000 exhibited objects from 50 fields of science and technology. The museum was founded on June 28, 1903, at a meeting of the Association...

, Munich, Germany). In 1840, the Woodward machine was developed from improving the Ramsden machine (placing the prime conductor above the disk(s)). Also in 1840, the Armstrong hydroelectric machine was developed and used steam as a charge carrier.

Friction operation


The presence of surface charge
Surface charge
Surface charge is the electric charge present at an interface. There are many different processes which can lead to a surface being charged, including adsorption of ions, protonation/deprotonation, and the application of an external electric field...

 imbalance means that the objects will exhibit attractive or repulsive forces. This surface charge imbalance, which leads to static electricity, can be generated by touching two differing surfaces together and then separating them due to the phenomena of contact electrification
Contact electrification
Contact electrification is an obsolete scientific theory from the Enlightenment that attempted to account for all the sources of electric charge known at the time. In the late 18th century, scientists developed sensitive instruments for detecting 'electrification', otherwise known as electrostatic...

 and the triboelectric effect
Triboelectric effect
The triboelectric effect is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated...

. Rubbing two non-conductive objects generates a great amount of static electricity. This is not just the result of friction; two non-conductive surfaces can become charged by just being placed one on top of the other. Since most surfaces have a rough texture, it takes longer to achieve charging through contact than through rubbing. Rubbing objects together increases amount of adhesive contact between the two surfaces. Usually insulators, e.g., substances that do not conduct electricity, are good at both generating, and holding, a surface charge. Some examples of these substances are rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

, plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

, glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

, and pith
Pith
Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In eudicots, pith is located in the center of the stem. In monocots, it extends also into flowering stems and roots...

. Conductive objects in contact generate charge imbalance too, but retain the charges only if insulated. The charge that is transferred during contact electrification is stored on the surface of each object. Note that the presence of electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

 does not detract from the electrostatic forces nor from the sparking, from the corona discharge
Corona discharge
In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized...

, or other phenomena. Both phenomena can exist simultaneously in the same system.

History


Frictional machines were, in time, gradually superseded by the second class of instrument mentioned above, namely, influence machines. These operate by electrostatic induction
Electrostatic induction
Electrostatic induction is a redistribution of electrical charge in an object, caused by the influence of nearby charges. Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762. Electrostatic generators, such as the Wimshurst machine, the...

 and convert mechanical work into electrostatic energy by the aid of a small initial charge which is continually being replenished and reinforced. The first suggestion of an influence machine appears to have grown out of the invention of Volta
Alessandro Volta
Count Alessandro Giuseppe Antonio Anastasio Gerolamo Umberto Volta was a Lombard physicist known especially for the invention of the battery in 1800.-Early life and works:...

's electrophorus
Electrophorus
An electrophorus is a capacitive generator used to produce electrostatic charge via the process of electrostatic induction. A first version of it was invented in 1762 by Swedish professor Johan Carl Wilcke,...

. The electrophorus is a single-plate capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...

 used to produce imbalances of electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

 via the process of electrostatic induction
Electrostatic induction
Electrostatic induction is a redistribution of electrical charge in an object, caused by the influence of nearby charges. Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762. Electrostatic generators, such as the Wimshurst machine, the...

. The next step was when Abraham Bennet, the inventor of the gold leaf electroscope
Electroscope
An electroscope is an early scientific instrument that is used to detect the presence and magnitude of electric charge on a body. It was the first electrical measuring instrument. The first electroscope, a pivoted needle called the versorium, was invented by British physician William Gilbert...

, described a "doubler of electricity" (Phil. Trans., 1787), as a device similar to the electrophorus, but that could amplify a small charge by means of repeated manual operations with three insulated plates, in order to make it observable in an electroscope. Erasmus Darwin
Erasmus Darwin
Erasmus Darwin was an English physician who turned down George III's invitation to be a physician to the King. One of the key thinkers of the Midlands Enlightenment, he was also a natural philosopher, physiologist, slave trade abolitionist,inventor and poet...

, W. Wilson, G. C. Bohnenberger, and (later, 1841) J. C. E. Péclet developed various modifications of Bennet's device. In 1788, William Nicholson
William Nicholson (chemist)
William Nicholson was a renowned English chemist and writer on "natural philosophy" and chemistry, as well as a translator, journalist, publisher, scientist, and inventor.-Early life:...

 proposed his rotating doubler, which can be considered as the first rotating influence machine. His instrument was described as "an instrument which by turning a winch produces the two states of electricity without friction or communication with the earth". (Phil. Trans., 1788, p. 403) Nicholson later described a "spinning condenser" apparatus, as a better instrument for measurements.

Others, including T. Cavallo
Tiberius Cavallo
Tiberius Cavallo was an Italian physicist and natural philosopher.-Life:He was born at Naples, where his father was a physician....

 (who developed the "Cavallo multiplier", a charge multiplier using simple addition, in 1795), John Read, Charles Bernard Desormes, and Jean Nicolas Pierre Hachette
Jean Nicolas Pierre Hachette
Jean Nicolas Pierre Hachette , French mathematician, was born at Mézières, where his father was a bookseller.For his early education he proceeded first to the college of Charleville, and afterwards to that of Reims...

, developed further various forms of rotating doublers. In 1798, The German scientist and preacher Gottlieb Christoph Bohnenberger, described the Bohnenberger machine, along with several other doublers of Bennet and Nicholson types in a book. The most interesting of these were described in the "Annalen der Physik" (1801). Giuseppe Belli, in 1831, developed a simple symmetrical doubler which consisted of two curved metal plates between which revolved a pair of plates carried on an insulating stem. It was the first symmetrical influence machine, with identical structures for both terminals. This apparatus was reinvented several times, by C. F. Varley, that patented a high power version in 1860, by Lord Kelvin (the "replenisher") 1868, and by A. D. Moore (the "dirod"), more recently. Lord Kelvin also devised a combined influence machine and electromagnetic machine, commonly called a mouse mill, for electrifying the ink in connection with his siphon recorder
Siphon recorder
The syphon or siphon recorder is an item of telecommunications equipment invented by William Thomson, 1st Baron Kelvin in 1858. It was used to automatically record the receipt of a telegraph message, as a wiggling ink line on a roll of paper tape...

, and a water-drop electrostatic generator (1867), which he called the "water-dropping condenser".

Between 1864 and 1880, W. T. B. Holtz
Wilhelm Holtz
Wilhelm Holtz was a German physicist who was a native of Saatel bei Barth, Mecklenburg. Between 1857 and 1862 he studied physics and natural sciences in Berlin, Dijon and Edinburgh...

 constructed and described a large number of influence machines which were considered the most advanced developments of the time. In one form, the Holtz machine consisted of a glass disk mounted on a horizontal axis which could be made to rotate at a considerable speed by a multiplying gear, interacting with induction plates mounted in a fixed disk close to it. In 1865, August J. I. Toepler
August Toepler
August Joseph Ignaz Toepler was a German physicist known for his experiments in electrostatics. In 1864 he applied Foucault's knife-edge test for telescope mirrors to the analysis of fluid flow and the shock wave. He named this new method schlieren photography, for which he is justifiably famous...

 developed an influence machine that consisted of two disks fixed on the same shaft and rotating in the same direction. In 1868, the Schwedoff machine had a curious structure to increase the output current. Also in 1868, several mixed friction-influence machine were developed, including the Kundt machine and the Carré machine. In 1866, the Piche machine (or Bertsch machine) was developed. In 1869, H. Julius Smith received the American patent for a portable and airtight device that was designed to ignite powder. Also in 1869, sectorless machines in Germany were investigated by Poggendorff
Johann Christian Poggendorff
Johann Christian Poggendorff , was a German physicist born in Hamburg.By far the greater and more important part of his work related to electricity and magnetism. Poggendorff is known for his electrostatic motor which is analogous to Wilhelm Holtz's electrostatic machine...

.

The action and efficiency of influence machines were further investigated by F. Rossetti
Francesco Rossetti
Francesco Rossetti was a notable Italian experimental physicist.Son of Giovanni Battista, he started his education in his natal town Trento. He then attended the University of Padova and, from 1854 to 1857, the University of Vienna, where he heard classes in mathematics, chemistry and physics, and...

, A. Righi
Augusto Righi
Augusto Righi was an Italian physicist and a pioneer in the study of electromagnetism. He was born and died in Bologna.His early research, conducted in Bologna between 1872 and 1880, was primarily in electrostatics...

, and F. W. G. Kohlrausch
Friedrich Kohlrausch
Friedrich Wilhelm Georg Kohlrausch was a German physicist who investigated the conductive properties of electrolytes and contributed to knowledge of their behaviour...

. E. E. N. Mascart
Éleuthère Mascart
Éleuthère Élie Nicolas Mascart was a noted French physicist, a researcher in optics and electricity.Mascart was born in Quarouble, Nord. He attended the École normale supérieure...

, A. Roiti, and E. Bouchotte also examined the efficiency and current producing power of influence machines. In 1871, sectorless machines were investigated by Musaeus. In 1872, Righi's electrometer was developed and was one of the first antecedents of the Van de Graaff generator. In 1873, Leyser developed the Leyser machine, a variation of the Holtz machine. In 1880, Robert Voss (a Berlin instrument maker) devised a form of machine in which he claimed that the principles of Toepler and Holtz were combined. The same structure become also known as the Toepler-Holtz machine. In 1878, the British inventor James Wimshurst
James Wimshurst
James Wimshurst was an English inventor, engineer and shipwright. Though Wimshurst did not patent his machines and the various improvements that he made to them, his refinements to the electrostatic generator led to its becoming widely known as the Wimshurst machine.-Biography:Wimshurst was born...

 started his studies about electrostatic generators, improving the Holtz machine, in a powerful version with multiple disks. The classical Wimshurst machine
Wimshurst machine
The Wimshurst influence machine is an electrostatic generator, a machine for generating high voltages developed between 1880 and 1883 by British inventor James Wimshurst ....

, that become the most popular form of influence machine, was reported to the scientific community by 1883, although previous machines with very similar structures were previously described by Holtz and Musaeus. In 1885, one of the largest-ever Wimshurst machines was built in England (it is now at the Chicago Museum of Science and Industry
Museum of Science and Industry (Chicago)
The Museum of Science and Industry is located in Chicago, Illinois, USA in Jackson Park, in the Hyde Park neighborhood adjacent to Lake Michigan. It is housed in the former Palace of Fine Arts from the 1893 World's Columbian Exposition...

). In 1887, Weinhold modified the Leyser machine with a system of vertical metal bar inductors with wooden cylinders close to the disk for avoiding polarity reversals. M. L. Lebiez described the Lebiez machine, that was essentially a simplified Voss machine (L'Électricien, April 1895, pp. 225–227). In 1894, Bonetti designed a machine with the structure of the Wimshurst machine, but without metal sectors in the disks. This machine is significantly more powerful than the sectored version, but it must usually be started with an externally-applied charge.

In 1898, the Pidgeon machine was developed with a unique setup by W. R. Pidgeon
W. R. Pidgeon
W. R. Pidgeon developed the Pidgeon machine, a electrostatic machine with a unique setup.-Biography:Pidgeon presented this machine to the Physical Society after several years of investigation into influence machines . The device was later reported in the Philosophical Magazine and the Electrical...

. On October 28 of that year, Pidgeon presented this machine to the Physical Society after several years of investigation into influence machines (beginning at the start of the decade). The device was later reported in the Philosophical Magazine (Dec. 1898, pg. 564) and the Electrical Review (Vol. XLV, pg. 748). A Pidgeon machine possesses fixed inductor
Inductor
An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...

s arranged in a manner that increases the electrical induction effect (and its electrical output is at least double that of typical machines of this type [except when it is overtaxed]). The essential features of the Pidgeon machine are, one, the combination of the rotating support and the fixed support for inducing charge, and, two, the improved insulation of all parts of the machine (but more especially of the generator's carriers). Pidgeon machines are a combination of a Wimshurst Machine and Voss Machine, with special features adapted to reduce the amount of charge leakage. Pidgeon machines excite themselves more readily than the best of these types of machines. In addition, Pidgeon investigated higher current "triplex" section machines (or "double machines with a single central disk") with enclosed sectors (and went on to receive British Patent 22517 (1899) for this type of machine).

Multiple disk machines and "triplex" electrostatic machines (generators with three disks) were also developed extensively around the turn of the century
Turn of the century
Turn of the century, in its broadest sense, refers to the transition from one century to another. The term is most often used to indicate a non-specific time period either before or after the beginning of a century....

. In 1900, F. Tudsbury discovered that enclosing a generator in a metallic chamber containing compressed air
Compressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....

, or better, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, the insulating properties
Electrical insulation
thumb|250px|[[Coaxial Cable]] with dielectric insulator supporting a central coreThis article refers to electrical insulation. For insulation of heat, see Thermal insulation...

 of compressed gases enabled a greatly improved effect to be obtained owing to the increase in the breakdown voltage of the compressed gas, and reduction of the leakage across the plates and insulating supports. In 1903, Alfred Wehrsen patented an ebonite rotating disk possessing embedded sectors with button contacts at the disk surface. In 1907, Heinrich Wommelsdorf reported a variation of the Holtz machine using this disk and inductors embedded in celluloid plates (DE154175; "Wehrsen machine"). Wommelsdorf also developed several high-performance electrostatic generators, of which the best known were his "Condenser machines" (1920). These were single disk machines, using disks with embedded sectors that were accessed at the edges.

Modern electrostatic generators



Electrostatic generators had a fundamental role in the investigations about the structure of matter, starting at the end of the 19th century. By the 1920s, it was evident that machines able to produce greater voltage were needed. The Van de Graaff generator
Van de Graaff generator
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate very high voltages on a hollow metal globe on the top of the stand. It was invented in 1929 by American physicist Robert J. Van de Graaff. The potential differences achieved in modern Van de Graaff...

was developed, starting in 1929, at MIT. The first model was demonstrated in October 1929. The basic idea was to use an insulating belt to transport electric charge to the interior of an insulated hollow terminal, where it could be discharged regardless of the potential already present on the terminal, that does not produce any electric field in its interior. The idea was not new, but the implementation using an electronic power supply to charge the belt was a fundamental innovation that made the old machines obsolete. The first machine used a silk ribbon bought at a five and dime store as the charge transport belt. In 1931 a version able to produce 1,000,000 volts was described in a patent disclosure. Nikola Tesla
Nikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...

 wrote a Scientific American article, "Possibilities of Electro-Static Generators" in 1934 concerning the Van de Graaff generator (pp. 132–134 and 163-165). Tesla stated, "I believe that when new types [of Van de Graaff generators] are developed and sufficiently improved a great future will be assured to them". High-power machines were soon developed, working on pressurized containers to allow greater charge concentration on the surfaces without ionization. Variations of the Van de Graaff generator were also developed for Physics research, as the Pelletron
Pelletron
A pelletron is a type of electrostatic particle accelerator similar to a Van de Graaff generator. Pelletrons have been built in many sizes, from small units producing voltages up to 500 kilovolts and beam energies up to 1 megaelectronvolt of kinetic energy, to the largest system, which has...

, that uses a chain with alternating insulating and conducting links for charge transport. Simplified Van de Graaff generators are commonly seen in demonstrations about static electricity, due to its high-voltage capability, producing the curious effect of making the hair of people touching the terminal, standing over an insulating support, stand up.

Between 1945 and 1960, the French researcher Noël Felici developed a series of high-power electrostatic generators, based on electronic excitation and using cylinders rotating at high speed and hydrogen in pressurized containers.

Fringe science and devices


These generators have been used, sometimes inappropriately and with some controversy, to support various fringe science
Fringe science
Fringe science is scientific inquiry in an established field of study that departs significantly from mainstream or orthodox theories, and is classified in the "fringes" of a credible mainstream academic discipline....

 investigations. In 1911, George Samuel Piggott received a patent for a compact double machine enclosed within a pressurized box for his experiments concerning radiotelegraphy and "antigravity". Much later (in the 1960s), a machine known as "Testatika" was built by German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...

, Paul Suisse Bauman, and promoted by a Swiss community, the Methernitha
Methernitha
Methernitha refers to two related entities, both founded by Paul Baumann : Methernitha Christian Alliance and Methernitha Cooperative...

ns. Testatika is an electromagnetic generator based on the 1898 Pidgeon electrostatic machine, said to produce "free energy" available directly from the environment.

See also

  • List of electrostatic generator patents
  • Electrostatic motor
    Electrostatic motor
    An electrostatic motor or capacitor motor is a type of electric motor based on the attraction and repulsion of electric charge.Often, electrostatic motors are the dual of conventional coil-based motors. They typically require a high voltage power supply, although very small motors employ lower...

  • Electrometer
    Electrometer
    An electrometer is an electrical instrument for measuring electric charge or electrical potential difference. There are many different types, ranging from historical hand-made mechanical instruments to high-precision electronic devices...

     (also known as the "electroscope")
  • Electret
    Electret
    Electret is a dielectric material that has a quasi-permanent electric charge or dipole polarisation. An electret generates internal and external electric fields, and is the electrostatic equivalent of a permanent magnet. Oliver Heaviside coined this term in 1885...

  • Static electricity
    Static electricity
    Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...


Further reading

  • Gottlieb Christoph Bohnenberger: Description of different electricity-doubler of a new device, along with a number of experiments on various subjects of electricity, etc.. Tübingen 1798.
  • William Holtz: On a new electrical machine .. In: Johann Poggendorff, CG Barth (Eds.): Annals of physics and chemistry. 126, Leipzig 1865, p. 157 - 171st
  • William Holtz: the higher charge on insulating surfaces by side pull and the transfer of this principle to the construction of induction machines .. In: Johann Poggendorff, CG Barth (eds): Annals of physics and chemistry. 130, Leipzig 1867, p. 128 - 136
  • William Holtz: The influence machine. In: F. Poske (Eds.): Annals of physics and chemistry. Julius Springer, Berlin 1904 (seventeenth year, the fourth issue).
  • O. Lehmann: Dr. J. Frick's physical technique. 2, Friedrich Vieweg und Sohn, Braunschweig 1909, p. 797 (Section 2).
  • F. Poske: New forms of influence machines .. In: F. Poske (eds) for the physical and chemical education. journal Julius Springer, Berlin 1893 (seventh year, second issue).
  • C. L. Stong, "Electrostatic motors are powered by electric field of the Earth". October, 1974. (PDF)
  • Oleg D. Jefimenko
    Oleg D. Jefimenko
    Oleg Dmitrovich Jefimenko - physicist and Professor Emeritus at West Virginia University.-Biography:...

     , "Electrostatic Motors: Their History, Types, and Principles of Operation". Electret Scientific, Star City, 1973.
  • G. W. Francis (Author) and Oleg D. Jefimenko (Editor), "Electrostatic Experiments: An Encyclopedia of Early Electrostatic Experiments, Demonstrations, Devices, and Apparatus". Electret Scientific, Star City, 2005.
  • V. E. Johnson, "Modern High-Speed Influence Machines; Their principles, construction and applications to radiography, radio-telegraphy, spark photography, electro-culture, electro-therapeutics, high-tension gas ignition, and the testing of materials". ISBN B0000EFPCO
  • Alfred W. Simon, "Quantitative Theory of the Influence Electrostatic Generator". Phys. Rev. 24, 690–696 (1924), Issue 6 – December 1924.
  • J. Clerk Maxwell, Treatise on Electricity and Magnetism (2nd ed.,Oxford, 1881), vol. i. p. 294
  • J. D. Everett, Electricity (expansion of part iii. of Deschanels Natural Philosophy) (London, 1901), ch. iv. p. 20
  • A. Winkelmann, Handbuch der Physik (Breslau, 1905), vol. iv. pp. 50–58 (contains a large number of references to original papers)
  • J. Gray, "Electrical Influence Machines, Their Historical Development and Modern Forms [with instruction on making them]" (London, I903). (J. A. F.)
  • Silvanus P. Thompson
    Silvanus P. Thompson
    Silvanus Phillips Thompson FRS was a professor of physics at the City and Guilds Technical College in Finsbury, England. He was elected to the Royal Society in 1891 and was known for his work as an electrical engineer and as an author...

    , The Influence Machine from Nicholson -1788 to 1888, Journ. Soc. Tel. Eng., 1888, 17, p. 569
  • John Munro, The Story Of Electricity (The Project Gutenberg Etext)
  • A. D. Moore (Editor), "Electrostatics and its Applications". Wiley, New York, 1973.
  • Oleg D. Jefimenko (with D. K. Walker), "Electrostatic motors". Phys. Teach. 9, 121-129 (1971).
  • W. R. Pidgeon, "An Influence-Machine". Proc. Phys. Soc. London 12(1)1 (October 1892) 406–411 and 16(1) (October 1897) 253–257.

External links