rheostat

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rhe·o·stat / ˈrēəˌstat/ • n. an electrical instrument used to control a current by varying the resistance.DERIVATIVES: rhe·o·stat·ic / ˌrēəˈstatik/ adj.

rheostat

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rheostat Variable resistor for regulating an electric current. The resistance element may be a metal wire, carbon or a conducting liquid. Rheostats are used to adjust generators, to dim lights and to control the speed of electric motors.