Sparks and arcs

From HvWiki

A spark is a conducting path in air produced by a strong electric field. An arc is a conducting path created by high temperatures. In both cases the path is a plasma.

Sparks

The voltage required to produce a spark is given by Paschen's law. A spark is a short-lived plasma trail blue to white in appearance, with jagged edges. If sufficient current and voltage are available, a spark can form into an arc.

Arcs

Arcs initiate at whatever distance the voltage of their power supply dictates (see Sparks above), but unlike a spark an arc can be drawn out. Depending on the current the power supply can source, the arc, once initiated, can be drawn several times longer than the distance it took to initiate it. Arcs range in color from dark purple to blinding white depending the current passing through them. The color relates to the composition of the gas, pressure (neon tubes create light by arcing), and temperature of the gas. Certain chemical compounds can alter the color of an arc, much like flame tests in chemistry.