History
The Ancient Greeks already knew that pieces of amber could attract lightweight particles after being rubbed. The amber becomes electrified by triboelectric effect, mechanical separation of charge in a dielectric. The Greek word for amber is ηλεκτρον ("elektron") and is the origin of the word "electricity".
Around 1650, Otto von Guericke built a crude electrostatic generator: 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 idea for the Leyden jar was discovered independently by two parties: German scientist and jurist Ewald Georg von Kleist, and Dutchmen Musschenbroek and Cunaeus. These scientists developed the Leyden jar while working under a theory of electricity that saw electricity as a fluid, and hoped to develop the jar to "capture" this fluid. In 1744 when von Kleist lined a glass jar with silver foil, and charged the foil with a friction machine. Kleist was convinced that a substantial electric charge could be collected when he received a significant shock from the device. The effects of this "Kleistian jar" were independently discovered around the same time by Dutch scientists Pieter van Musschenbroek and Cunaeus at the University of Leiden. Musschenbroek communicated on it with the French scientific community where it was called the Leyden jar.
Daniel Gralath was the first to combine several jars in parallel into a capacitor "battery" to increase the total possible stored charge. The term "battery" was coined by Benjamin Franklin, who likened it to a battery of cannon (cannons grouped in a common place). The term was later used for arrangements of multiple electrochemical cells. 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 dielectrics and the need to reduce their size and inductance for use in the new technology of radio caused the Leyden jar to evolve into the modern compact form of capacitor.
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