An electrostatic generator, or electrostatic machine, is a mechanical device 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. They develop electrostatic charges of opposite signs rendered to two conductors, using only electric forces.
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, and variations as the Pelletron, also find use in physics research. Electrostatic generators are classically separated on two kinds: friction machines and influence machines.
FRICTION MACHINE
History
The first electrostatic generators are called friction machines because of the friction in the generation process. A primitive form of frictional electrical machine was constructed 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.[1] , but inspired many later machines that used rotating globes. Isaac Newton suggested the use of a glass globe instead of a sulphur one (Optics, 8th Query). Francis Hauksbee improved the basic design
Generators were further advanced when G. M. Bose of Wittenberg added a collecting conductor (an insulated tube or cylinder supported on silk strings). 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, 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, 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 constructed a large electrostatic machine of high quality for his experiments (currently on display at the Teylers Museum in the Netherlands).
In 1785, N. Rouland constructed a silk belted machine which rubbed two grounded hare fur covered tubes. Edward Nairne 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 possessed a machine similar to the van Marum machine for his research (which is now at the Deutsches Museum, 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.
References:
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, and variations as the Pelletron, also find use in physics research. Electrostatic generators are classically separated on two kinds: friction machines and influence machines.
FRICTION MACHINE
History
Typical friction machine using a glass globe, common in the 18th century
Martinus van Marum's Electrostatic generator at Teylers Museum
The first electrostatic generators are called friction machines because of the friction in the generation process. A primitive form of frictional electrical machine was constructed 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.[1] , but inspired many later machines that used rotating globes. Isaac Newton suggested the use of a glass globe instead of a sulphur one (Optics, 8th Query). Francis Hauksbee improved the basic design
Generators were further advanced when G. M. Bose of Wittenberg added a collecting conductor (an insulated tube or cylinder supported on silk strings). 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, 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, 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 constructed a large electrostatic machine of high quality for his experiments (currently on display at the Teylers Museum in the Netherlands).
In 1785, N. Rouland constructed a silk belted machine which rubbed two grounded hare fur covered tubes. Edward Nairne 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 possessed a machine similar to the van Marum machine for his research (which is now at the Deutsches Museum, 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.
References:
- http://en.wikipedia.org
- Schiffer, Michael Brian (2003). Bringing the Lightning Down: Benjamin Franklin and Electrical Technology in the Age of Enlightenment. Univ. of California Press. ISBN 0520248295. http://books.google.com/books?id=QQuk6bH2apcC&printsec=frontcover&vq=electrostatic&dq=otto+guericke&lr=&as_brr=0.,p.18-19
- Hauksbee, Francis (1709). Psicho-Mechanical Experiments On Various Subjects. R. Brugis.
- http://www.coe.ufrj.br/~acmq/bonetti.html Instructions for building a Bonetti machine
