rheostats

Noun

rheostat (plural rheostats)

1. An electrical resistor with two terminals, the resistance of which can be varied continuously by moving a knob or slider to regulate the flow of an electric current.
   • [page 309] As the principal use of this instrument is to adjust or regulate the circuit so that any constant degree of force may be obtained, I have called it a Rheostat. […] [page 311] The rheostat, especially under the form last described, may be usefully employed as a regulator of a voltaic...1843 June 15 (date delivered), Charles Wheatstone, “XIII. The Bakerian Lecture.—An Account of Several New Instruments and Processes for Determining the Constants of a Voltaic Circuit.”, in...
   1. Such a device used to regulate the brightness of an electric light; a dimmer.
      • The light in the radio cabin was very dim, the rheostat of the angled table lamp had been turned down until only a faint pool of yellow fell on the scratched metal of the table, […]1966, Alistair MacLean, “Dusk Monday – 3 a.m. Tuesday”, in When Eight Bells Toll, 1st American edition, Garden City, N.Y.: Doubleday & Company, →OCLC, page 8
2. (figuratively) A notional device which causes some quality to vary.
   • The world had dimmed a little when she was gone, as if there were a rheostat on the sun and somebody had turned it down, just one notch.1968, John D[ann] MacDonald, The Girl in the Plain Brown Wrapper, Philadelphia, Pa.; New York, N.Y.: J[oshua] B[allinger] Lippincott Company, published 1973, →ISBN, page 34