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Wimshurst Machine

 
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Wimshurst machine
 
 
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The Wimshurst machine is an electrostatic device
Electrostatic generator

An electrostatic generator, or electrostatic machine, is a mechanical device that produces static electricity, or electricity at high voltage and low continuous current....
 for generating high voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
s developed between 1880 and 1883 by British
United Kingdom

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom , the UK or Britain,is a sovereign state located off the northwestern coast of continental Europe....
 inventor
Inventor

An inventor is a person who creates or discovers a new method, form, device or other useful means. The word inventor comes form the latin verb invenire, invent-, to find....
 James Wimshurst
James Wimshurst

James Wimshurst was an England 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....
 (1832 – 1903). It has a distinctive appearance with two large contra-rotating discs mounted in a vertical plane, two cross bars with metallic brushes, and a spark gap formed by two metal spheres.

Description
These machines belong to a class of generators called influence machines, which separate electric charge
Electric charge

Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields....
s through 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....
, or influence.






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Encyclopedia


The Wimshurst machine is an electrostatic device
Electrostatic generator

An electrostatic generator, or electrostatic machine, is a mechanical device that produces static electricity, or electricity at high voltage and low continuous current....
 for generating high voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
s developed between 1880 and 1883 by British
United Kingdom

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom , the UK or Britain,is a sovereign state located off the northwestern coast of continental Europe....
 inventor
Inventor

An inventor is a person who creates or discovers a new method, form, device or other useful means. The word inventor comes form the latin verb invenire, invent-, to find....
 James Wimshurst
James Wimshurst

James Wimshurst was an England 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....
 (1832 – 1903). It has a distinctive appearance with two large contra-rotating discs mounted in a vertical plane, two cross bars with metallic brushes, and a spark gap formed by two metal spheres.

Description


These machines belong to a class of generators called influence machines, which separate electric charge
Electric charge

Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields....
s through 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....
, or influence. Earlier machines in this class were developed by Wilhelm Holtz
Wilhelm Holtz

Wilhelm Holtz was a German physicist who was a native of Saatel bei Barth, Germany, Mecklenburg. Between 1857 and 1862 he studied physics and natural sciences in Berlin, Dijon and Edinburgh....
 (1865 and 1867), August Toepler (1865), and J. Robert Voss (1880). The older machines were less efficient and exhibited an unpredictable tendency to switch their polarity. The Wimshurst did not have this defect.

In a Wimshurst machine, the two insulated disks 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 disk. 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 a spark jumps across the gap.

The machine is self-starting, meaning that external electrical energy is not required to create the initial charge. However, it does require mechanical power
Power (physics)

In physics, power is the rate at which mechanical work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time....
 to turn the disks against the electric field, and it is this energy that the machine converts into electric power. The output of the Wimshurst machine is essentially a constant current that is proportional to the area covered by the metal sectors and to the rotation speed. 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 jar
Leyden jar

The Leyden jar, or Leiden jar, is a device that "stores" static electricity between two electrodes on the inside and outside of a jar. It was invented in 1745 by Pieter van Musschenbroek , in Leiden, The Netherlands....
s, an early type of capacitor
Capacitor

A capacitor or condenser is a Passive component electronic component consisting of a pair of electrical conductor separated by a dielectric....
 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 disk's diameter in length and several tens of microamperes.

See also


  • 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 electrostatically stable voltages on a hollow metal globe....


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