It has a distinctive appearance with two large contra-rotating discs mounted in a vertical plane, two crossed bars with metallic brushes, and a spark gap formed by two metal spheres.
These machines belong to a class of electrostatic generators called influence machines, which separate electric charges through electrostatic induction, or influence, not depending on friction for their operation. Earlier machines in this class were developed by Wilhelm Holtz (1865 and 1867), August Toepler (1865), J. Robert Voss (1880), and others. The older machines are less efficient and exhibit an unpredictable tendency to switch their polarity. The Wimshurst does not have this defect.
In a Wimshurst machine, the two insulated discs and their metal sectors rotate in opposite directions passing the crossed metal neutralizer bars and their brushes. An imbalance of charges is induced, amplified, and collected by two pairs of metal combs with points placed near the surfaces of each disc. These collectors are mounted on insulating supports and connected to the output terminals. The positive feedback increases the accumulating charges exponentially until the dielectric breakdown voltage of the air is reached and an electric spark jumps across the gap.
The machine is theoretically not self-starting, meaning that if none of the sectors on the discs has any electrical charge there is nothing to induce charges on other sectors. In practice, even a small residual charge on any sector is enough to start the process going once the discs start to rotate. The machine will only work satisfactorily in a dry atmosphere. It requires mechanical power to turn the disks against the electric field, and it is this energy that the machine converts into the electric power of the spark. The steady state output of the Wimshurst machine is a direct (non-alternating) current that is proportional to the area covered by the metal sector, the rotation speed, and a complicated function of the initial charge distribution. The insulation and the size of the machine determine the maximum output voltage that can be reached. The accumulated spark energy can be increased by adding a pair of Leyden jars, an early type of capacitor suitable for high voltages, with the jars’ inner plates independently connected to each of the output terminals and the jars’ outer plates interconnected. A typical Wimshurst machine can produce sparks that are about a third of the disc's diameter in length and several tens of microamperes.
The available voltage gain can be understood by noting that the charge density on oppositely charged sectors, between the neutralizer bars, is nearly uniform across the sectors, and thus at low voltage, while the charge density on same charged sectors, approaching the collector combs, peaks near the sector edges, at a consequently high voltage relative to the opposite collector combs.
Wimshurst machines were used during the 19th century in physics research. They were also occasionally used to generate high voltage to power the first-generation Crookes X-ray tubes during the first two decades of the 20th century, although Holtz machines and induction coils were more commonly used. Today they are only used in science museums and education to demonstrate the principles of electrostatics.
The two contra-rotating insulating discs (usually made of glass) have a number of metal sectors stuck onto them. The machine is provided with four small earthed brushes (two on each side of the machine on conducting shafts at 90° to each other), plus a pair of charge-collection combs. The conducting shafts, that hold the brushes on a typical Wimshurst machine, would form the shape of an "X", if one could see through the insulating discs, as they are perpendicular to each other. The charge-collection combs are typically mounted along the horizontal and equally contact the outer edges of both front and back discs. The collection combs on each side are usually connected to respective Leyden jars.
Any small charge on either of the two discs suffices to begin the charging process. Suppose, therefore, that the back disc has a small, net electrostatic charge. For concreteness, assume this charge is positive (red) and that the back disc ([A] lower chain) rotates counter-clockwise (right to left). As the charged sector (moving red square) rotates to the position of the brush ([Y] down arrow tip) next to front disc ([B] upper chain near center), it induces a polarization of charge on the conducting shaft ([Y-Y1] upper horizontal black line) holding the brush, attracting negative (green) charge to the near side ([Y] upper square becoming green), so that positive (red) charge accumulates on the far side (across the disc, 180 degrees away) ([Y1] upper square becoming red). The shaft's polarized charges attach to the nearest sectors on disc B, resulting in negative charge on B [Y] closer to the original positive charge on A, and positive charge on the opposite side of B [Y1]. After an additional 45° rotation ([Z] near lower chain middle), the positive (red) charge on A (lower chain) is repelled by a positive (red) charge on B ([Z] upper chain) approaching. The first collection comb ([Z] arrow-tipped lines to triangles) encountered allows both positive (red) charges to leave the sectors neutral (squares becoming black), and accumulate in the Leyden jar anode (red triangle) attracted to the Leyden jar cathode (green triangle). The charge completes the cycle across the discs when a spark (yellow zigzag) discharges the Leyden jar (red and green triangles).
As B rotates 90° clockwise (left to right), the charges that have been induced on it line up with the brushes next to disc A [X, X1]. The charges on B induce the opposite polarization of the A-brushes' shaft, and the shaft's polarization is transferred to its disc. Disc B keeps rotating and its charges are accumulated by the nearest charge-collection combs.
Disc A rotates 90° so that its charges line up with the brush of disc B [Y, Y1], where an opposite charge-polarization is induced on the B conducting shaft and the nearest sectors of B, similar to the description two paragraphs above.
The process repeats, with each charge polarization on A inducing polarization on B, inducing polarization on A, etc. All of these induced positive and negative charges are collected by combs to charge the Leyden jars, electrical charge-storage devices similar to capacitors. The mechanical energy required to separate the opposing charges on the adjacent sectors provides the energy source for the electrical output.
The Armstrong effect is the physical process by which static electricity is produced by the friction of a fluid. It was first discovered in 1840 when an electrical spark resulted from water droplets being swept out by escaping steam from a boiler. The effect is named after William Armstrong, who later became 1st Baron Armstrong, who was one of several people involved in discovering the effect and investigating the processes involved. Using this principle Armstrong went on to invent what he called the Armstrong Hydroelectric Machine, which, despite its name, generated static electricity and not hydroelectric power.Dibner Institute for the History of Science and Technology
The Dibner Institute for the History of Science and Technology (1992–2006) was a research institute established at MIT, and housed in a renovated building (E56) on campus at 38 Memorial Drive, overlooking the Charles River.Electrophorus
An electrophorus or electrophore is a simple manual capacitive electrostatic 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, but Italian scientist Alessandro Volta improved and popularized the device in 1775, and is sometimes erroneously credited with its invention. The word electrophorus was coined by Volta from the Greek ήλεκτρον ('elektron'), and ϕέρω ('phero'), meaning 'electricity bearer'.Electrostatic discharge
Electrostatic discharge (ESD) is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short, or dielectric breakdown. A buildup of static electricity can be caused by tribocharging or by electrostatic induction. The ESD occurs when differently-charged objects are brought close together or when the dielectric between them breaks down, often creating a visible spark.
ESD can create spectacular electric sparks (lightning, with the accompanying sound of thunder, is a large-scale ESD event), but also less dramatic forms which may be neither seen nor heard, yet still be large enough to cause damage to sensitive electronic devices. Electric sparks require a field strength above approximately 40 kV/cm in air, as notably occurs in lightning strikes. Other forms of ESD include corona discharge from sharp electrodes and brush discharge from blunt electrodes.
ESD can cause harmful effects of importance in industry, including explosions in gas, fuel vapor and coal dust, as well as failure of solid state electronics components such as integrated circuits. These can suffer permanent damage when subjected to high voltages. Electronics manufacturers therefore establish electrostatic protective areas free of static, using measures to prevent charging, such as avoiding highly charging materials and measures to remove static such as grounding human workers, providing antistatic devices, and controlling humidity.
ESD simulators may be used to test electronic devices, for example with a human body model or a charged device model.Electrostatic generator
An electrostatic generator, or electrostatic machine, is an electromechanical generator that produces static electricity, or electricity at high voltage 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, 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. Electrostatic generators operate by using manual (or other) power to transform mechanical work into electric energy. Electrostatic generators develop electrostatic charges 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 electrode. The charge is generated by one of two methods: either the triboelectric effect (friction) or electrostatic induction.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, caused by the influence of nearby charges. In the presence of a charged body, an insulated conductor develops a positive charge on one end and a negative charge on the other end. 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 Van de Graaff generator and the electrophorus, use this principle. Due to induction, the electrostatic potential (voltage) is constant at any point throughout a conductor. Electrostatic Induction is also responsible for the attraction of light nonconductive objects, such as balloons, paper or styrofoam scraps, to static electric charges. Electrostatic induction laws apply in dynamic situations as far as the quasistatic approximation is valid. Electrostatic induction should not be confused with Electromagnetic induction.Fred Judd
Frederick Charles (Fred) Judd, (1914–1992) is known for his work in amateur radio, particularly his designs of the Slim Jim and ZL Special aerial antennas. He was also an inventor and proselytiser of early British electronic music.Henry Wimshurst
Henry Wimshurst (1804–1884) was a 19th-century British shipbuilder. Wimshurst was in business at Ratcliffe Cross Dock in east London. He is remembered primarily as the builder of Archimedes, the world's first propeller-driven steamship.While Wimshurst cannot take credit for Archimedes' revolutionary propulsion system—which was the invention of Francis Pettit Smith—he was an "ardent supporter" of Smith and his technological breakthrough. He would later claim to have proposed an improved, two-bladed version of Smith's original propeller which was subsequently installed on the vessel.After completing Archimedes in 1839, Wimshurst built a second screw-propelled steamship in 1840, Novelty, described as the world's first screw-propelled cargo ship and the first screw-propelled ship to make a commercial voyage.Wimshurst himself had an inventive turn of mind, and filed a number of patents during the course of his career. In 1854, he built an experimental rotary steam engine, which when installed in a 300-ton screw-propelled ship, reportedly achieved an rpm of 45 and a top speed of 14 mph in tests conducted by the firm of Boulton & Watt. By comparison, a pair of conventional direct-acting engines later installed in the same ship achieved an rpm of 28 and a top speed of only 8 mph. A few years prior in 1850, Wimshurst developed an instrument for measuring the power exerted by a propeller shaft—a forerunner of the torsion meter, an instrument for measuring the power transmitted by turbines.Henry Wimshurst was the father of James Wimshurst, a late-19th century inventor who developed the Wimshurst machine and an early device for generating X-rays.History of electrical engineering
This article details the history of electrical engineering.Index of physics articles (W)
The index of physics articles is split into multiple pages due to its size.
To navigate by individual letter use the table of contents below.Ion wind
Ion wind, ionic wind, coronal wind or electric wind is the airflow induced by electrostatic forces linked to corona discharge arising at the tips of some sharp conductors (such as points or blades) subjected to high voltage relative to ground. Ion wind is an electrohydrodynamic phenomenon. Ion wind generators can also be considered electrohydrodynamic thrusters.
The term “ionic wind” is considered a misnomer due to misconceptions that only positive and negative ions were primarily involved in the phenomenon. A 2018 study found that electrons play a larger role than the negative ions during the negative voltage period. As a result, the term “electric wind” has been suggested as a more accurate terminology.This phenomenon is now used in an MIT ionic wind plane, the first solid state plane, developed in 2018.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 to its becoming widely known as the Wimshurst machine.List of scientific demonstrations
This is a list of scientific demonstrations used in educational demonstrations and popular science lectures.Museum of Science and Industry (Chicago)
The Museum of Science and Industry (MSI) is located in Chicago, Illinois, in Jackson Park, in the Hyde Park neighborhood between Lake Michigan and The University of Chicago. It is housed in the former Palace of Fine Arts from the 1893 World's Columbian Exposition. Initially endowed by Julius Rosenwald, the Sears, Roebuck and Company president and philanthropist, it was supported by the Commercial Club of Chicago and opened in 1933 during the Century of Progress Exposition.
Among the museum's exhibits are a full-size replica coal mine, German submarine U-505 captured during World War II, a 3,500-square-foot (330 m2) model railroad, the command module of Apollo 8, and the first diesel-powered streamlined stainless-steel passenger train (Pioneer Zephyr).
David R. Mosena has been president and CEO of the private, non-profit museum since 1998.Rahmi M. Koç Museum
The Rahmi M. Koç Museum is a private industrial museum in Istanbul, Turkey dedicated to history of transport, industry and communications. Rahmi M. Koç, member of the wealthiest dynasty in Turkey and retired boss of the Koç Group, founded the museum in 1991, which was opened on December 13, 1994. The museum is located in the suburb of Hasköy on the north shore of the Golden Horn and situated in two historical buildings connected to each other. It is open to public every day except Monday. The museum's general manager is Ertuğrul Duru.
A sister museum, but smaller in size, the Çengelhan Rahmi M. Koç Museum opened its doors to the residents of Ankara in 2005.Static electricity
Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is named in contrast with current electricity, which flows through wires or other conductors and transmits energy.A static electric charge can be created whenever two surfaces contact and separate, and at least one of the surfaces has a high resistance to electric current (and is therefore an electrical insulator). The effects of static electricity are familiar to most people because people can feel, hear, and even see the spark as the excess charge is neutralized when brought close to a large electrical conductor (for example, a path to ground), or a region with an excess charge of the opposite polarity (positive or negative). The familiar phenomenon of a static shock – more specifically, an electrostatic discharge – is caused by the neutralization of charge.W. R. Pidgeon
W. R. Pidgeon developed the Pidgeon machine, an electrostatic machine with a unique setup.William Coates (technician)
William Albert Coates better known as Bill Coates MBE (7 November 1919-7 October 1993) was a science communicator, lecturer and technician who worked at the Royal Institution in London from 1948 to 1986 and was a popular figure on television shows. As a lecture assistant he designed experiments for, and appeared alongside Lawrence Bragg numerous times as part of the televised Royal Institution Christmas Lectures. He was awarded the Bragg Medal in 1975.Wimshurst
Wimshurst is an English surname. Notable people with the surname include:
Henry Wimshurst (1804–1884), English shipbuilder
James Wimshurst (1832–1903), English inventor, engineer and shipwright
Wimshurst machine, an electrostatic generator
Ken Wimshurst (1938–2017), English footballer and manager