Liquid rheostat

A liquid rheostat or water rheostat or salt water rheostat is a type of variable resistor. This may be used as a dummy load or as a starting resistor for large slip ring motors.

In the simplest form it consists of a tank containing brine or other electrolyte solution, in which electrodes are submerged to create an electrical load. The electrodes may be raised or lowered into the liquid to respectively decrease or increase the electrical resistance of the load. To stabilize the load, the mixture must not be allowed to boil.