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An electric arc between two nails. An electric arc (or arc discharge) is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma, which may produce visible light. An arc discharge is initiated either by thermionic emission or by field ...
An arc flash is the light and heat produced from an electric arc supplied with sufficient electrical energy to cause substantial damage, harm, fire, or injury. Electrical arcs experience negative incremental resistance, which causes the electrical resistance to decrease as the arc temperature increases.
An arc fault is a high power discharge of electricity between two or more conductors. This discharge generates heat, which can break down the wire's insulation and trigger an electrical fire. Arc faults can range in current from a few amps up to thousands of amps, and are highly variable in strength and duration.
With a constant pressure, the voltage needed to cause an arc reduced as the gap size was reduced but only to a point. As the gap was reduced further, the voltage required to cause an arc began to rise and again exceeded its original value. For a given gas, the voltage is a function only of the product of the pressure and gap length.
If the power supply continues to supply current, the spark will evolve into a continuous discharge called an electric arc. An electric spark can also occur within insulating liquids or solids, but with different breakdown mechanisms from sparks in gases. Sometimes, sparks can be dangerous. They can cause fires and burn skin.
Electrical breakdown may be a momentary event (as in an electrostatic discharge), or may lead to a continuous electric arc if protective devices fail to interrupt the current in a power circuit. In this case electrical breakdown can cause catastrophic failure of electrical equipment, and fire hazards.
Along with the similar brush discharge, the corona is often called a "single-electrode discharge", as opposed to a "two-electrode discharge"—an electric arc. [ 1 ] [ 2 ] [ 3 ] A corona forms only when the conductor is widely enough separated from conductors at the opposite potential that an arc cannot jump between them.
Every time an electrical power device (for example: heaters, lamps, motors, transformers or similar power loads) turns on or off, its switch, relay or contactor transitions either from a CLOSED to an OPEN state ("BREAK") or from an OPEN to a CLOSED state ("MAKE"), under load, an electrical arc occurs between the two contact points (electrodes) of the switch.