Leyden jar

An early capacitor made from a glass jar with conductive coatings inside and out. It stores static electric charge and releases it in a sudden discharge.

Capacitance: A measure of how much electric charge a system stores per unit of voltage. The jar’s ability to store charge is described by its capacitance.
Ewald Georg von Kleist: A German cleric and physicist who independently devised an early charge-storing jar in 1745. His experiment preceded the better-known Leiden demonstration.
Electrostatic generator: A machine that produces high voltages by separating and accumulating electric charge. Generators charged Leyden jars for experiments requiring a substantial stored discharge.
Electrostatics: The study of electric charges at rest and the forces and fields they produce. The jar became a central experimental instrument in early electrostatics.
Electric field: A physical field that exerts force on electric charges. Charge on the jar’s coatings creates a field through the glass.
Pieter van Musschenbroek: A Dutch physicist who reported a powerful electric shock from a jar in 1746. His report publicized the device that became known as the Leyden jar.
Franklin's kite experiment: Benjamin Franklin’s 1752 investigation of whether lightning is electrical, using a kite during a thunderstorm. Franklin used a Leyden jar to collect and test electrical charge in related experiments.
Electrical capacitance unit: The farad is the SI unit of capacitance, named after Michael Faraday. Later capacitor theory quantified the charge-storage property first explored with jars.
Dielectric: An electrical insulator that polarizes in an applied electric field. The glass separates the coatings and strengthens the jar’s charge storage.
Andreas Cunaeus: A Leiden lawyer associated with the 1746 experiment that revealed the jar’s strong shock. Accounts connect his handling of the charged jar to the famous demonstration.

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