An arc is a visible electrical discharge that occurs when current jumps between two conductive points through a gas such as air, xenon, or argon.
In electrical systems, an arc forms when a voltage difference is strong enough to ionize gas and allow current to flow between two electrodes. This process creates an intense burst of light and heat, known as an arc discharge. Arcing can occur naturally in open-air conditions or within enclosed environments like circuit breakers or contactors. While some arcs are deliberately used in applications such as welding or industrial lighting, others are unintended and may indicate a fault condition in electrical systems.
In commercial and industrial wiring environments, arc events are treated with caution due to their potential to damage equipment or pose fire hazards. Arcs can result from worn insulation, conductor separation, or accidental contact during maintenance. For this reason, materials used in cable construction, such as insulation, jacketing, and shielding, are often selected to resist arc propagation and withstand elevated temperatures if arcing occurs.
Monitored and regulated under organizations such as the National Fire Protection Association (NFPA), Institute of Electrical and Electronics Engineers (IEEE), and Underwriters Laboratories (UL), particularly in reference to electrical safety and fire mitigation.
The first practical use of an electrical arc as a light source was pioneered in 1809 by Sir Humphry Davy. His carbon arc lamp became one of the earliest forms of electric lighting and laid the foundation for arc-based technologies still used in industrial processes today.