An arc discharge is a type of electrical discharge that occurs when a current flows through the air or another gas, creating a bright, continuous arc of plasma. This phenomenon typically happens when a high voltage is applied across two conductive electrodes, causing the air between them to ionize and become conductive. The resulting arc can produce intense heat and light. Arc discharges are commonly used in various applications, such as in arc welding, where they help join metals by melting them together. They are also found in lightning, which is a natural form of arc discharge, and in gas discharge lamps, which produce light through similar principles.