Electric current
Arc Sources produce an electric arc. Electric current moving in the gap between the two electrodes creates a bright blue light. They can typically be found in follow spots and moving fixtured. One of their downsides is that they cannot be dimmed Therefore, the light can either be turned on or off. They can also use mechanical dimmers, such as dousers, that are made with slats or an iris that moves to limit the light leaving the fixture.