![Van de graaff generator sm](https://upload.wikimedia.org/wikipedia/commons/8/82/Van_de_graaff_generator_sm.jpg)
An electrostatic generator, or electrostatic machine, is an
electrical generator
In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power ( chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, g ...
that produces ''
static electricity'', or electricity at
high voltage
High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, ''high voltage'' refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant sp ...
and low
continuous current
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even ...
. The knowledge of static electricity dates back to the earliest civilizations, but for millennia it remained merely an interesting and mystifying
phenomenon
A phenomenon ( : phenomena) is an observable event. The term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be directly observed. Kant was heavily influenced by Gottfried ...
, 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 is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describ ...
.
Electrostatic generators operate by using manual (or other) power to transform
mechanical work
In physics, work is the energy transferred to or from an object via the application of force along a displacement. In its simplest form, for a constant force aligned with the direction of motion, the work equals the product of the force stre ...
into
electric energy
Electrical energy is energy related to forces on electrically charged particles and the movement of electrically charged particles (often electrons in wires, but not always). This energy is supplied by the combination of electric current and electr ...
, or using
electric currents. Manual electrostatic generators develop
electrostatic
Electrostatics is a branch of physics that studies electric charges at rest ( static electricity).
Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amb ...
charge
Charge or charged may refer to:
Arts, entertainment, and media Films
* '' Charge, Zero Emissions/Maximum Speed'', a 2011 documentary
Music
* ''Charge'' (David Ford album)
* ''Charge'' (Machel Montano album)
* ''Charge!!'', an album by The Aqu ...
s of opposite signs rendered to two conductors, using only electric forces, and work by using moving plates, drums, or belts to carry electric charge to a high
potential
Potential generally refers to a currently unrealized ability. The term is used in a wide variety of fields, from physics to the social sciences to indicate things that are in a state where they are able to change in ways ranging from the simple r ...
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials d ...
.
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 tube
An X-ray tube is a vacuum tube that converts electrical input power into X-rays. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast ...
s,
particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams.
Large accelerators are used for fundamental research in particle ...
s,
spectroscopy, medical applications, sterilization of food, and nuclear physics experiments. Electrostatic generators such as the
Van de Graaff generator
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate electric charge on a hollow metal globe on the top of an insulated column, creating very high electric potentials. It produces very high voltage
...
, and variations as the
Pelletron
A Pelletron is a type of electrostatic generator, structurally similar to a Van de Graaff generator. Pelletrons have been built in many sizes, from small units producing voltages up to 500 kilovolts (kV) and beam energies up to 1 megaelectronvolt ...
, also find use in physics research.
Electrostatic generators can be divided into categories depending on how the charge is generated:
*Friction machines use the
triboelectric effect
The triboelectric effect (also known as triboelectric charging) is a type of contact electrification on which certain materials become electrically charged after they are separated from a different material with which they were in contact. Rubb ...
(electricity generated by contact or friction)
*Influence machines use
electrostatic induction
Electrostatic induction, also known as "electrostatic influence" or simply "influence" in Europe and Latin America, is a redistribution of electric charge in an object that is caused by the influence of nearby charges. In the presence of a charg ...
*Others
Friction machines
History
![Electrostatic generator Teylers Museum](https://upload.wikimedia.org/wikipedia/commons/e/ed/Electrostatic_generator_Teylers_Museum.jpg)
The first electrostatic generators are called ''friction machines'' because of the
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of ...
in the generation process. A primitive form of frictional machine was invented around 1663 by
Otto von Guericke, using a sulphur globe that could be rotated and rubbed by hand. It may not actually have been rotated during use and was not intended to produce electricity (rather cosmic virtues), but inspired many later machines that used rotating globes.
Isaac Newton
Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a " natural philosopher"), widely recognised as one of the grea ...
suggested the use of a glass globe instead of a sulphur one. About 1706
Francis Hauksbee
Francis Hauksbee the Elder FRS (1660–1713), also known as Francis Hawksbee, was an 18th-century English scientist best known for his work on electricity and electrostatic repulsion.
Biography
Francis Hauksbee was the son of draper and common c ...
improved the basic design, with his frictional electrical machine that enabled a glass sphere to be rotated rapidly against a woollen cloth.
Generators were further advanced when, about 1730, Prof.
Georg Matthias Bose
Georg Matthias Bose (22 September 1710 – 17 September 1761), also known as Mathias Bose, was a famous electrical experimenter in the early days of the development of electrostatics. He is credited with being the first to develop a way of tem ...
of Wittenberg added a collecting conductor (an insulated tube or cylinder supported on silk strings). Bose was the first to employ the "
prime conductor
Georg Matthias Bose (22 September 1710 – 17 September 1761), also known as Mathias Bose, was a famous electrical experimenter in the early days of the development of electrostatics. He is credited with being the first to develop a way of temp ...
" 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,
William Watson William, Willie, Bill or Billy Watson may refer to:
Entertainment
* William Watson (songwriter) (1794–1840), English concert hall singer and songwriter
* William Watson (poet) (1858–1935), English poet
* Billy Watson (actor) (1923–2022), A ...
'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.
Johann Heinrich Winckler
Johann Heinrich Winckler (12 March 1703 – 18 May 1770) was a German physicist and philosopher.
Biography Early life
Winckler was born in Wingendorf, a village in Silesia.Klemme, Heiner F; Kuehn, Manfred. (2016). ''The Bloomsbury Dictionary of E ...
, professor of physics at
Leipzig
Leipzig ( , ; Upper Saxon: ) is the most populous city in the German state of Saxony. Leipzig's population of 605,407 inhabitants (1.1 million in the larger urban zone) as of 2021 places the city as Germany's eighth most populous, as ...
, substituted a leather cushion for the hand. During 1746,
Jan Ingenhousz
Jan (or John) Ingenhousz or Ingen-Housz FRS (8 December 1730 – 7 September 1799) was a Dutch-born British physiologist, biologist and chemist.
He is best known for discovering photosynthesis by showing that light is essential to the process ...
invented electric machines made of plate glass. Experiments with the electric machine were largely aided by the discovery of the
Leyden Jar
A Leyden jar (or Leiden jar, or archaically, sometimes Kleistian jar) is an electrical component that stores a high-voltage electric charge (from an external source) between electrical conductors on the inside and outside of a glass jar. It typ ...
. This early form of the
capacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
, with conductive coatings on either side of the glass, can accumulate a charge of electricity when connected with a source of electromotive force.
The electric machine was soon further improved by
Andrew (Andreas) Gordon, a Scotsman and 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 about 1746, and in 1762,
John Canton
John Canton FRS (31 July 1718 – 22 March 1772) was a British physicist. He was born in Middle Street Stroud, Gloucestershire, to a weaver, John Canton (b. 1687) and Esther (née Davis). As a schoolboy, he became the first person to deter ...
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.
[Maver, William Jr.: "Electricity, its History and Progress", The Encyclopedia Americana; a library of universal knowledge, vol. X, pp. 172ff. (1918). New York: Encyclopedia Americana Corp.] In 1768,
Jesse Ramsden
Jesse Ramsden FRS FRSE (6 October 1735 – 5 November 1800) was a British mathematician, astronomical and scientific instrument maker. His reputation was built on the engraving and design of dividing engines which allowed high accuracy measure ...
constructed a widely used version of a plate electrical generator.
In 1783, Dutch scientist
Martin van Marum of Haarlem designed a
large electrostatic machine of high quality with glass disks 1.65 meters in diameter for his experiments. Capable of producing voltage with either polarity, it was built under his supervision by
John Cuthbertson of Amsterdam the following year. The generator is currently on display at the
Teylers Museum
Teylers Museum () is an art, natural history, and science museum in Haarlem, Netherlands. Established in 1778, Teylers Museum was founded as a centre for contemporary art and science. The historic centre of the museum is the neoclassical Oval R ...
in Haarlem.
In 1785, N. Rouland constructed a silk-belted machine that rubbed two grounded tubes covered with hare fur.
Edward Nairne
Edward Nairne (1726 – 1 September 1806) was English optician and scientific instrument maker.
Biography
Nairne was born in Sandwich, England. He was apprenticed to the optician Matthew Loft in 1741 and established his own business at 20 Cor ...
developed an electrostatic generator for medical purposes in 1787 that had the ability to generate either positive or negative electricity, the first of these 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 Simon Ohm (, ; 16 March 1789 – 6 July 1854) was a German physicist and mathematician. As a school teacher, Ohm began his research with the new electrochemical cell, invented by Italian scientist Alessandro Volta. Using equipment of his o ...
possessed a machine similar to the Van Marum machine for his research (which is now at the
Deutsches Museum
The Deutsches Museum (''German Museum'', officially (English: ''German Museum of Masterpieces of Science and Technology'')) in Munich, Germany, is the world's largest museum of science and technology, with about 28,000 exhibited objects from ...
, Munich, Germany). In 1840, the
Woodward machine was developed by improving the 1768 Ramsden machine, placing the prime conductor above the disk(s). Also in 1840, the
Armstrong hydroelectric machine was developed, using steam as a charge carrier.
Friction operation
The presence of
surface charge 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 phenomenon of the
triboelectric effect
The triboelectric effect (also known as triboelectric charging) is a type of contact electrification on which certain materials become electrically charged after they are separated from a different material with which they were in contact. Rubb ...
. Rubbing two non-conductive objects generates a great amount of static electricity. This is not 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
Insulator may refer to:
* Insulator (electricity), a substance that resists electricity
** Pin insulator, a device that isolates a wire from a physical support such as a pin on a utility pole
** Strain insulator, a device that is designed to work ...
, 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, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, an ...
,
plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
,
glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
, and
pith
Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which in some cases can store starch. In eudicotyledons, pith is located in the center of the stem. In monocotyledons, it ext ...
.
Conductive
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. Electric current is gene ...
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 does not detract from the electrostatic forces nor from the sparking, from the
corona discharge
A corona discharge is an electrical discharge caused by the ionization of a fluid such as air surrounding a conductor (material), conductor carrying a high voltage. It represents a local region where the air (or other fluid) has undergone e ...
, or other phenomena. Both phenomena can exist simultaneously in the same system.
Influence machines
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, also known as "electrostatic influence" or simply "influence" in Europe and Latin America, is a redistribution of electric charge in an object that is caused by the influence of nearby charges. In the presence of a charg ...
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's ''
electrophorus''. The electrophorus is a single-plate
capacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
used to produce imbalances of
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
via the process of
electrostatic induction
Electrostatic induction, also known as "electrostatic influence" or simply "influence" in Europe and Latin America, is a redistribution of electric charge in an object that is caused by the influence of nearby charges. In the presence of a charg ...
.
The next step was when
Abraham Bennet, the inventor of the gold leaf
electroscope
The electroscope is an early scientific instrument used to detect the presence of electric charge on a body. It detects charge by the movement of a test object due to the Coulomb electrostatic force on it. The amount of charge on an object is ...
, 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. In 1788,
William Nicholson 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.
Erasmus Darwin, W. Wilson, G. C. Bohnenberger, and (later, 1841) J. C. E. Péclet developed various modifications of Bennet's 1787 device.
Francis Ronalds
Sir Francis Ronalds FRS (21 February 17888 August 1873) was an English scientist and inventor, and arguably the first electrical engineer. He was knighted for creating the first working electric telegraph over a substantial distance. In 1816 ...
automated the generation process in 1816 by adapting a pendulum bob as one of the plates, driven by clockwork or a steam engine – he created the device to power his
electric telegraph
Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems ...
.
Others, including
T. Cavallo (who developed the "
Cavallo multiplier", a charge multiplier using simple addition, in 1795),
John Read,
Charles Bernard Desormes
Charles Bernard Desormes (; 3 June 1777 – 30 August 1862) was a French physicist and chemist. He determined the ratio of the specific heats of gases in 1819. He did this and almost all his scientific work in collaboration with his son-in-law N ...
, and
Jean Nicolas Pierre Hachette
Jean Nicolas Pierre Hachette (6 May 1769 – 16 January 1834), 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 ...
, 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
Giuseppe Francesco Antonio Maria Gioachino Raimondo Belli (7 September 1791 – 21 December 1863) was an Italian poet, famous for his sonnets in Romanesco, the dialect of Rome.
Biography
Giuseppe Francesco Antonio Maria Gioachino Raimondo Bell ...
, 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
William Thomson, 1st Baron Kelvin, (26 June 182417 December 1907) was a British mathematician, mathematical physicist and engineer born in Belfast. Professor of Natural Philosophy at the University of Glasgow for 53 years, he did important ...
(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, and a water-drop electrostatic generator (1867), which he called the "''
water-dropping condenser''".
=Holtz machine
=
![Holtz influence machine](https://upload.wikimedia.org/wikipedia/commons/f/fb/Holtz_influence_machine.jpg)
Between 1864 and 1880,
W. T. B. Holtz 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 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
Carré is a French word, which means "square". ''Carré'' may also refer to:
People
* Carré (surname)
* Carré Otis, American model and actress
Places
* Fort Carré, sixteenth-century fort in France
* Vieux Carré, French Quarter of New Orlea ...
. 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.
The action and efficiency of influence machines were further investigated by
F. Rossetti,
A. Righi, and
Friedrich Kohlrausch.
E. E. N. Mascart,
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 Leyser is a surname. Notable people with the surname include:
* Polykarp Leyser (disambiguation), multiple people
*Ottoline Leyser (born 1965), British plant biologist
*Henrietta Leyser
Henrietta Leyser is an English historian. She is an expe ...
, a variation of the Holtz machine. In 1880,
Robert Voss
Robert Andrew Voss (born 9 February 1953) is a British businessman in the metals industry. Voss was appointed Lord Lieutenant of Hertfordshire
This is an incomplete list of people who have served as Lord Lieutenant of Hertfordshire. From 1660 t ...
(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.
=Wimshurst machine
=
![Wimshurst](https://upload.wikimedia.org/wikipedia/commons/3/35/Wimshurst.jpg)
In 1878, the British inventor
James Wimshurst
James Wimshurst (13 April 1832 – 3 January 1903) 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 ...
started his studies about electrostatic generators, improving the Holtz machine, in a powerful version with multiple disks. The classical Wimshurst machine, that became 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). The
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 (1832–1903).
It has a distinctive appearance with two large contra-ro ...
is a considerably simple machine; it works, as all influence machines, with electrostatic induction of charges, which means that it uses even the slightest existing charge to create and accumulate more charges, and repeats this process for as long as the machine is in action. Wimshurst machines are composed of: two insulated disks attached to pulleys of opposite rotation, the disks have small conductive (usually metal) plates on their outward-facing sides; two double-ended brushes that serve as charge stabilizers and are also the place where induction happens, creating the new charges to be collected; two pairs of collecting combs, which are, as the name implies, the collectors of electrical charge produced by the machine; two Leyden Jars, the capacitors of the machine; a pair of electrodes, for the transfer of charges once they have been sufficiently accumulated. The simple structure and components of the Wimshurst Machine make it a common choice for a homemade electrostatic experiment or demonstration, these characteristics were factors that contributed to its popularity, as previously mentioned.
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
Lebiez (; vls, Sint-Vaast) is a Communes of France, commune in the Pas-de-Calais Departments of France, department in the Hauts-de-France region of France.
Geography
A small village situated 10 miles (16 km) east of Montreuil-sur-Mer at th ...
, that was essentially a simplified
Voss machine (''L'Électricien'', April 1895, pp. 225–227). In 1893, Bonetti patented 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.
=Pidgeon machine
=
In 1898, the
Pidgeon machine was developed with a unique setup by
W. R. Pidgeon. On October 28 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'' (December 1898, pg. 564) and the ''Electrical Review'' (Vol. XLV, pg. 748). A Pidgeon machine possesses fixed
inductor
An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
s arranged in a manner that increases the
electrostatic induction effect (and its electrical output is at least double that of typical machines of this type
xcept 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 20th century. In 1900,
F. Tudsbury discovered that enclosing a generator in a metallic chamber containing
compressed air
Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and o ...
, or better,
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
, the
insulating properties 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.
Van de Graaff
The Van de Graaff generator was invented by American physicist
Robert J. Van de Graaff
Robert Jemison Van de Graaff (December 20, 1901 – January 16, 1967) was an American physicist, noted for his design and construction of high-voltage Van de Graaff generators. The bulk of his career was spent in the Massachusetts Institute of T ...
in 1929 at
MIT
The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...
as a particle accelerator.
The first model was demonstrated in October 1929. In the Van de Graaff machine, an insulating belt transports electric charge to the interior of an insulated hollow metal high voltage terminal, where it is transferred to the terminal by a "comb" of metal points. The advantage of the design was that since there was no electric field in the interior of the terminal, the charge on the belt could continue to be discharged onto the terminal regardless of how high the voltage on the terminal was. Thus the only limit to the voltage on the machine is
ionization
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
of the air next to the terminal. This occurs when the electric field at the terminal exceeds the
dielectric strength
In physics, the term dielectric strength has the following meanings:
*for a pure electrically insulating material, the maximum electric field that the material can withstand under ideal conditions without undergoing electrical breakdown and beco ...
of air, about 30 kV per centimeter. Since the highest electric field is produced at sharp points and edges, the terminal is made in the form of a smooth hollow sphere; the larger the diameter the higher the voltage attained. 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.
The Van de Graaff generator was a successful particle accelerator, producing the highest energies until the late 1930s when the
cyclotron
A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Janu ...
superseded it. The voltage on open air Van de Graaff machines is limited to a few million volts by air breakdown. Higher voltages, up to about 25 megavolts, were achieved by enclosing the generator inside a tank of pressurized insulating gas. This type of Van de Graaff particle accelerator is still used in medicine and research. Other variations were also invented for physics research, such as the
Pelletron
A Pelletron is a type of electrostatic generator, structurally similar to a Van de Graaff generator. Pelletrons have been built in many sizes, from small units producing voltages up to 500 kilovolts (kV) and beam energies up to 1 megaelectronvolt ...
, that uses a chain with alternating insulating and conducting links for charge transport.
Small Van de Graaff generators are commonly used in
science museum
A science museum is a museum devoted primarily to science. Older science museums tended to concentrate on static displays of objects related to natural history, paleontology, geology, industry and industrial machinery, etc. Modern trends in mu ...
s and science education to demonstrate the principles of static electricity. A popular demonstration is to have a person touch the high voltage terminal while standing on an insulated support; the high voltage charges the person's hair, causing the strands to stand out from the head.
Others
Not all electrostatic generators use the triboelectric effect or electrostatic induction. Electric charges can be generated by electric currents directly. Examples are ionizers and
ESD guns.
Applications
Gridded ion thruster
EWICON
An electrostatic
vaneless ion wind generator
A vaneless ion wind generator or power fence is a device that generates electrical energy by using the wind to move charged particles across an electric field.
Ion wind generators are not commercially available, though working prototypes and pro ...
, the EWICON, has been developed by The School of Electrical Engineering, Mathematics and Computer Science at
Delft University of Technology
Delft University of Technology ( nl, Technische Universiteit Delft), also known as TU Delft, is the oldest and largest Dutch public technical university, located in Delft, Netherlands. As of 2022 it is ranked by QS World University Rankings among ...
(TU Delft). Its stands near Mecanoo, an architecture firm. The main developers were Johan Smit and Dhiradj Djairam. Other than the wind, it has no moving parts. It is powered by the wind carrying away charged particles from its collector.
The design suffers from poor efficiency.
Dutch Windwheel
The technology developed for EWICON has been reused in the Dutch Windwheel.
Dutch Windwheel
/ref>
Air ioniser
Fringe science and devices
These generators have been used, sometimes inappropriately and with some controversy, to support various fringe science
Fringe science refers to ideas whose attributes include being highly speculative or relying on premises already refuted. Fringe science theories are often advanced by persons who have no traditional academic science background, or by researchers ...
investigations. In 1911, George Samuel Piggott received a patent for a compact double machine enclosed within a pressurized box for his experiments concerning radiotelegraphy
Wireless telegraphy or radiotelegraphy is transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term ''wireless telegraphy'' was also used for other experimental technologies for ...
and " antigravity". Much later (in the 1960s), a machine known as "Testatika" was built by German engineer, Paul Suisse Bauman, and promoted by a Swiss community, the Methernithans. Testatika is an electromagnetic generator based on the 1898 Pidgeon electrostatic machine, said to produce "free energy" available directly from the environment.
See also
* Electrostatic motor
An electrostatic motor or capacitor motor is a type of electric motor based on the attraction and repulsion of electric charge.
An alternative type of electrostatic motor is the spacecraft electrostatic ion drive thruster where forces and motion ...
* Electrometer
An electrometer is an electrical instrument for measuring electric charge or electrical potential difference. There are many different types, ranging from historical handmade mechanical instruments to high-precision electronic devices. Modern ...
(also known as the "electroscope")
* Electret
An electret (formed as a portmanteau of ''electr-'' from "electricity" and ''-et'' from "magnet") is a dielectric material that has a quasi-permanent electric charge or dipole polarization (electrostatics), polarisation. An electret generates int ...
* Static electricity
Static electricity is an imbalance of electric charges within or on the surface of a material or between materials. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is na ...
References
Further reading
*
Beschreibung unterschiedlicher Elektrizitätsverdoppler von einer neuen Einrichtung nebst einer Anzahl von Versuchen üb. verschiedene Gegenstände d. Elektrizitätslehre
escription of different electricity-doubler of a new device, along with a number of experiments on various subjects of electricityTübingen 1798.
*
*Wilhelm 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
*Wilhelm 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 Dmitrovich Jefimenko (October 14, 1922, Kharkiv, Ukrainian SSR – May 14, 2009, Morgantown, West Virginia, Morgantown, West Virginia, United States) was a physicist and Professor Emeritus at West Virginia University.
Biography
Jefimenko recei ...
, "''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
*
* J. Clerk Maxwell, Treatise on Electricity and Magnetism (2nd ed.,Oxford, 1881), vol. i. p. 294
* Joseph David Everett
Prof Joseph David Everett DCL FRSE (1831–1904) was an English physicist, professor of natural philosophy at Queen's College, Belfast.
Life
Born at Rushmere, near Ipswich, Suffolk, on 11 September 1831, he was the eldest son of Joseph David Eve ...
, ''Electricity'' (expansion of part iii. of Augustin Privat-Deschanel's "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 ith instruction on making them'" (London, I903). (J. A. F.)
* Silvanus P. Thompson
Silvanus Phillips Thompson (19 June 1851 – 12 June 1916) 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 eng ...
, 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).
*
*
External links
Electrostatic Generator - Interactive Java Tutorial
National High Magnetic Field Laboratory
*
* "''How it works
'". triquartz.co.uk.
* Antonio Carlos M. de Queiroz, "
'".
**"
'".
*"
Doublers of Electricity
'", 2007 Phys. Educ. 42 156–162.
American Museum of Radio: Electrostatic Machines
* "
'". Experiments with non conventional energy technologies.
* Sir William Thomson (Lord Kelvin
William Thomson, 1st Baron Kelvin, (26 June 182417 December 1907) was a British mathematician, mathematical physicist and engineer born in Belfast. Professor of Natural Philosophy at the University of Glasgow for 53 years, he did important ...
), "
On Electric Machines Founded on Induction and Convection
'". Philosophical Magazine, January 1868.
* M. Hill and D. J. Jacobs, "
A novel Kelvin Electrostatic Generator
'", 1997 Phys. Educ. 32 60–63.
* Paolo Brenni (Author) and Willem Hackmann (Editor), "
'". Bulletin of the Scientific Instrument Society No. 63 (1999)
*