Leyden Jar (Edited from Wikipedia)

SUMMARY

A Leyden jar, or jar, is a device that "stores" static between two on the inside and outside of a jar. A Leyden jar typically consists of a glass jar with metal foil cemented to the inside and the outside surfaces, and a metal terminal projecting vertically through the jar lid to make contact with the inner foil. It was the original form of a (originally known as a "condenser").

It was invented independently by German cleric Ewald Georg von Kleist on 11 October 1745 and by Dutch scientist of Leiden (Leyden) in 1745– 1746. The invention was named after the city.

The Leyden jar was used to conduct many early experiments in electricity, and its discovery was of fundamental importance in the study of . The Leyden jar was the first means of storing an which then could be discharged at the experimenter's will. Leyden jars are still used in education to demonstrate the principles of electrostatics.

HISTORY

The Ancient Greeks already knew that pieces of could attract lightweight particles after being rubbed. The amber becomes electrified by the mechanical separation of charge (such as by rubbing it with a cloth). The Greek word for amber is “elektron” and is the origin of the word "electricity".

Around 1650, built a crude : a sulphur ball that rotated on a shaft. When Guericke held his hand against the ball and turned the shaft quickly, a static electric charge built up. This experiment inspired the development of several forms of "friction machines", that greatly helped in the study of electricity.

The Leyden jar was effectively discovered independently by two people: German deacon Ewald Georg von Kleist, who made the first discovery; and the Dutch scientists Pieter van Musschenbroek and Andreas Cunaeus who figured out how it worked only when held in the hand.

1 Despite its mundane and safe appearance, the Leyden jar is a high voltage device, and electrical energy collected within it from friction may be as high as 35,000 volts. The ball on the tip of the rod is a corona ball to prevent leakage of the energy into the air by point discharge (electricity tends to more easily leak into the air through a sharp point than through a round ball).

Ewald Georg von Kleist (aka JG von Kleist) discovered the immense storage capability of the Leyden jar while working under a theory of electricity that saw electricity as a fluid. He hoped a glass jar filled with alcohol would "capture" this fluid. He was the deacon (an officer of the Church who ministers to the poor and needy) at the cathedral of Camin in Pomerania.

In 1744 von Kleist tried to accumulate electricity in a small medicine bottle filled with alcohol with a nail inserted in the cork. He was following up on an experiment developed by another man where electricity had been sent though water to set alcoholic spirits (like whiskey) on fire. He attempted to charge the bottle from a large metallic conductor suspended above his friction machine.

Kleist was convinced that a substantial electric charge could be collected and held within the glass which he knew would provide an obstacle to the escape of the 'fluid'. He received a significant shock from the device when he accidentally touched the nail through the cork while still cradling the bottle in his other hand. He corresponded with a number of electrical experimenters, but didn't understand the significance of his hand (a good conductor) holding the bottle—and both he and his correspondents were afraid to hold the device when told that the shock could throw them across the room. It took some time before Kleist's student associates at Leyden worked out that the hand provided an essential component of the device.

Musschenbroek and Cunaeus

For this reason, the Leyden Jar's invention was long credited to the Leyden physics professor, Pieter van Musschenbroek who also ran a family foundry (which cast brass miniature cannons) and a small business called "The Eastern Lamp." His business made scientific and medical instruments for the new university courses in physics and for scientific gentlemen keen to establish their own 'cabinets' of curiosities and instruments.

Andreas Cuneaus appears to have been the first to receive communications from von Kleist about the storage capacity of the jar. He attempted to duplicate the experiment using a glass of beer, but couldn't make it work. He then worked with the Professor of Physics at Leyden University, and they eventually charged a jar of water with electricity only by holding it in the hand, rather than mounting it on an insulating block. Cunaeus

2 and Musschenbroek also received severe shocks, and Musschenbroek communicated the experiment to the wider French scientific community.

Musschenbroek's outlet in France for the sale of his company's 'cabinet' devices was the a man named Nollet (who ran a similar business). Nollet then gave the electrical storage device the name "Leyden Jar" and promoted it as a special type of flask to his market of wealthy men with scientific curiosity. The "Kleistian jar" was therefore promoted as the Leyden Jar as having been discovered by Pieter van Musschenbroek and his assistant Andreas Cunaeus at the University of Leiden.

Daniel Gralath was the first to connect several jars in parallel to increase the total possible stored charge. The term "battery" was coined by for these combinations, who likened it to a battery of cannon (cannons grouped in a common place).

The term was later used for combinations of multiple electrochemical cells, which is the modern meaning of the term "battery". By the middle of the 19th century, the Leyden jar had become common enough for writers to assume their readers knew of and understood its basic operation.

Around the turn of the century it began to be widely used in spark-gap transmitters and medical electrotherapy equipment. By the early 20th century, improved (insulating material) and the need to reduce their size and undesired electrical properties of and resistance for use in emerging radio technology caused the Leyden jar to evolve into the modern compact form of capacitor.

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