Electrical discharges through air: What voltage is required to cause arcs and sparks?

摘要

Physicists and electrical engineers have long studied the phenomenon of gas breakdown. Normally, air does not conduct electric current, but under certain circumstances, this can change and air becomes an electrical conductor. This process is called "gas breakdown" or an "electrical discharge." Students in science classes demonstrate it when they connect an electrical source to two bare metal wires separated at a certain distance in air. If the voltage is raised sufficiently, an arc can occur between the two electrodes, as metal wires are used for this purpose. The arc is visible as a luminous, whitish path that may be straight or meander between the two electrodes. Current flows along this path and the arc is visible because of intense thermal radiation from the ionized particles that are formed along the path.