Media Contributed by Rick
"Dissectible" Leyden jar Drawing of a "dissectible" Leyden jar, from 1876 physics book. This experimental apparatus, invented by American statesman and scientist Benjamin Franklin, was used to illustrate an erroneous belief that the charge on a Leyden jar does not reside on the metal plates, but on the glass jar dielectric. The jar was assembled and charged with electricity. If the jar was then disassembled into its parts, it was found that the parts were not charged and could be handled without creating a spark. However, if the jar was then reassembled, a spark could be obtained between the inner and outer metal plates. This was supposed to show that the charge in Leyden jars, and all capacitors, is stored in the dielectric, not the metal plates. However, it is now known that this was a special effect caused by the high voltage on the Leyden jar. When the jar is disassembled, the charge is deposited on the glass by corona discharge. Handling does not remove much of the charge, so when the jar is reassembled there is enough left to cause a spark. In general the charge in capacitors such as Leyden jars is stored on the plates.
Leyden jar Drawing of a Leyden jar from a 1913 physics book. A Leyden jar is an antique piece of physics apparatus that can store electric charge; it was the first form of capacitor. It consists of a glass jar coated on the inside and outside with metal foil. The foils stop well short of the mouth of the jar so that the charge can't arc between the foils through the mouth. A brass rod electrode pierces the wooden stopper and extends into the jar, and from it hangs a metal chain which makes contact with the inner foil. The jar is charged by grounding the outside foil and applying electricity from an electrostatic machine to the electrode.
Discovery of the Leyden jar in Musschenbroek's lab Artist's conception of the discovery of the Leyden jar. In 1746, Andreas Cunaeus, an assistant in the laboratory of Pieter von Muschenbroek in Leyden, attempts to "condense" electricity in a glass of water. The rotating glass sphere (right) is an electrostatic machine. The static electricity generated by the hands rubbing on it is transferred through the chain to the suspended metal bar, and from it via the hanging wire into the glass of water. The glass acted as a capacitor, and a large charge built up in the water, and an equal charge of the opposite polarity built up in Cunaeus' hand holding the glass. When Cunaeus reached up to pull the wire out of the water, he got a severe shock, much worse than an electrostatic machine could give, because the amount of charge stored was much larger than the terminal of an electrostatic machine could store. Cunaeus took two days to recover. Musschenbroek was also impressed by the powerful shock he received from the device, writing, "I would not take a second shock for the crown of France". Reports of the experiment were widely circulated, and scientists began to investigate the charge storage ability of these "Leyden flasks". Eventually the water was replaced by foil coatings on the inside and outside of the jar to store the charge.
Frederick William, Elector of Brandenburg cropped from The Elector by Frans Luycx
The Academy building of Leiden University in 1614 Illustrium Hollandiae Westfrisiae ordinum alma academia Leidensis / Dedication portraits and portraits of Leiden professors, along with 4 scenes of university, library, anatomical room & hortus
