Abstract: A direct current plasma arc furnace includes a tank having a crucible delimiting a chamber to receive material to be melted and/or treated; refractory walls surrounding the crucible outer surface; a metallic frame covering the refractory walls; and a heating system for heating the received material. The heating system includes two electrodes acting as cathode and anode, respectively, wherein the first electrode is a movable electrode to project vertically into the chamber. The crucible is part of an anode system also having the second electrode and at least one part connecting the crucible and second electrode. The crucible receives and holds material to be melted and/or treated and provides electric conduction for the flow of current to heat the material, such that the voltage potential difference between the cathode and any point of the crucible surface defined to be in contact with the material is the same.