An electric arc is an electrical current that is intentionally or unintentionally discharging itself across a gap between two electrodes via a gas, vapor, or air and expending a relatively low voltage across the conductors. The heat and light produced by this arc is usually intense, and can be used for specific applications, such as arc welding or spotlight illumination. Unintended results may include fires, shock hazards, and property damage.
In 1801, British Chemist and inventor, Sir Humphry Davy, demonstrated an electric arc to his fellows in the London Royal Society, and offered the name, the electric arc. This demonstration was followed by the further studies of the electrical arc, as illustrated by Russian scientist, Vasily V. Petrov in 1802. Further advances in early electrical arc studies produced such industry-important inventions as arc welders.
Compared to a spark, which is only momentary, an arc discharge is a continuous electrical current that develops so much heat from the charge carrying ions or electrons that it can vaporize or melt anything within the range of the arc. An arc can be sustained in either DC or AC electrical circuits, and it needs to include some resistance so that increased current does not go unchecked and completely destroy the actual source of the circuit with its heat and energy draw.
Electric arcs are used in some camera flashes, spotlights for stage lighting, fluorescent lighting, arc welding, arc furnaces (for making steel and substances like calcium carbide), and in plasma cutters (in which compressed air is combined with a powerful arc and converted into a plasma that has the capability of instantaneously cutting through steel).
Electrical arcs can also be extremely dangerous when not intended. Situations where an electric arc is created in an uncontrolled environment, as in the case of an arc flash, can cause personal injury, death, fire, equipment damage, and property loss.