Leyden jar Capacitance Shock Commentary

Ewald Georg von Kleist, Pieter van Musschenbroek electromagnetism

Leyden jar

• Von Kleist and van Musschenbroek
• had the same teacher in Leyden,
• Willem’s Gravesande,
• and invented the same device,
• the Leyden jar.
• They thought electricity
• was a fluid, so why not
• fill a jar with water
• and place in it a brass rod
• to capture an electric charge?
• The glass of the jar
• became a dielectric,
• separating the water inside
• from a metal foil wrapped around the jar
• or, originally, from the hand holding the jar.
• The Leyden jar preceded
• the electric battery
• and enabled storage of electricity
• for serious study by Daniel Gralath,
• Alessandro Volta, Benjamin Franklin, and others.
• Volta used a Leyden jar
• to fire a pistol at fifty kilometers.
• Franklin used one to store
• an electric charge from rainclouds.
• Martinus van Marum used Leyden jars
• for electrolysis of metal salts.
• Marconi used one in his spark-gap transmitter.

Capacitance

• The Leyden jar was the first capacitor.
• and the original unit for capacitance
• was the jar.
• The modern unit is the farad
• in honor of Michael Faraday.
• One coulomb of charge
• on each side of the capacitor
• causing a voltage across the device
• of one volt
• is a capacitance of one farad.
• One jar is a little over
• one billionth of a farad.
• Modern supercapacitors have capacities
• up to ten thousand farads.

Shock

• Von Kleist and van Musschenbroek’s assistant
• were both shocked to discover
• how much electricity their Leyden jars discharged.