I'm highly interested in building my own small arc furnace for hobby use. Thus, I want to understand the nature of electrical arcs before proceeding to have maximum control over my design. So far, I know that electrical arcs form when the dielectric strength of the material (in this case, a gas) is overcome. Once this barrier is overcome, the gas becomes locally ionized, allowing electricity to flow with relative ease. What I don't understand is how the arc sustains itself. From what I understand, this plasma formed has very low electrical resistance. Without significant resistance to generate heat, how is the plasma sustained? I also want to know how one would control the intensity of the arc and thus the temperature of the furnace, but I feel that the answer to the previous question will lead into this.