= Electric arc
{wiki}
An <electric arc> is a sustained <electrical discharge> through an ionized gas, carrying substantial <electric current> in a conducting <plasma> channel. Heating and ionization maintain conductivity after the initial breakdown. An arc can join electrodes even though the cold gas between them is normally a poor conductor. In arc <welding>, the discharge supplies heat to a joint; in a switch, an unintended arc can prolong current after contacts separate. Its <current-voltage characteristic> can differ strongly from an ordinary resistor, so replacing it by one fixed resistance can miss the discharge dynamics.
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