Franklin bells are an early demonstration of electric charge

Electric charge

Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

 designed to work with a Leyden jar

Leyden jar

A Leyden jar, or Leiden jar, is a device that "stores" static electricity between two electrodes on the inside and outside of a jar. It was invented independently by German cleric Ewald Georg von Kleist on 11 October 1745 and by Dutch scientist Pieter van Musschenbroek of Leiden in 1745–1746. The...

. The bells consist of a metal stand with a crossbar, from which hang three bells. The outer two bells hang from conductive metal chains, while the central bell hangs from a nonconductive thread. In the spaces between these bells hang two metal clappers, small pendulums, which hang from nonconductive threads. A short metal chain hangs from the central bell. This chain is put in contact with the inner surface of a Leyden jar, while the outside surface of the jar is put in contact with the metal stand. The central bell takes its charge from the inner surface of the jar, while the outer surface charges the two bells on the conductive chains; this causes the bells to have a potential difference equal to that between the inner and outer surfaces of the jar. The hanging metal clappers will be attracted to one bell, will touch it, pick up its charge, and be repelled; they will then swing across to the other bell, and do the same there. Each time the clappers touch a bell, charge is transferred between the inner and outer surfaces of the Leyden jar. When the jar is completely discharged, the bells will stop ringing.

Franklin bells are only a qualitative indicator of electric charge and were used for simple demonstrations, not for research. They were invented by Benjamin Franklin

Benjamin Franklin

Dr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...

 in the 18th century during his experimentation with electricity.

See also

• Oxford Electric Bell
  Oxford Electric Bell
  The Oxford Electric Bell or Clarendon Dry Pile is an experimental electric bell that was set up in 1840 and which has rung almost continuously ever since. It is located in the foyer of the Clarendon Laboratory at the University of Oxford, England...
  
  , a set of electrostatic bells in the University of Oxford still ringing continuously since 1840.