The electric arc may be defined as a discharge ofelectricity between two
electrodes in a gas or vaporthat has a voltage drop atthe cathode ofthe order
ofthe minimum ionizing or minimum exciting potential ofthe gas or vapor.
The arc is a self-sustained discharge capable ofsupporting large currents by
providing its own mechanism for electron emission from the negative electrode.
Nature has provided us withthe electric arc in the form oflightning since time
immemorial, but it was not until the development ofthe voltaic pile that the
arc was first studied in the laboratory by Sir Humphrey Davy around 1810