A variable‐area water rheostat has been applied to the problem of current control in electric arc and plasma generating equipment. Resistance between 0.5 and 30 ohms can be obtained by adjusting the height of circulating water which surrounds pairs of fixed vertical aluminum plates. The electrolyte is ordinary city water which is circulated through the tank and discharged. No special filtering, pumping, or other treatment is used. The unit is located in the open air outside the laboratory and all control functions are operated from a remote switching panel. The unit has been operated using a maximum of 125 amp at 400 v dc and 1000 amp at 230 v dc.