As nouns the difference between reostat and rheostat
is that reostat is dated form of rheostat while rheostat is an electrical resistor, with two terminals, whose resistance is continuously variable by moving a knob or slider.
rheostat
English
Noun
(
en noun)
An electrical resistor, with two terminals, whose resistance is continuously variable by moving a knob or slider.
Synonyms
* dimmer (when applied to lights)