rheostat

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...
   • The temperature was kept constant by taking pyrometer readings at the beginning, after the third set of observations, and after the sixth set of observations, and making slight adjustments in the heating-current rheostats when necessary.1921 July (date written), William Schriever, The Simple Rigidity of a Drawn Tungsten Wire at Incandescent Temperatures: A Thesis Presented to the Faculty of the Graduate College of the State...
   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
      • [W]e decided we needed to carry our own theatre lighting. […] [H]e looked out for us two very large ancient round lamps with thick 'Fresnel' lenses and tall, heavy stands. To dim these lamps, there was a pair of huge rheostats mounted on a thick ply board, that inspired in the operator a constant...2023, Paul Farmer, “Touring One & All!”, in After the Miners’ Strike: A39 and Cornish Political Theatre versus Thatcher’s Britain, volume 1, Cambridge, Cambridgeshire: Open Book Publishers, →DOI...
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
   • You could see the giant's scorn and fury dim down all at once, as if it were on a rheostat. Obviously he was beginning to process the implications in terms of public opinion, gawker opinion, if this was in fact the girl's brother.2004, Tom Wolfe, “The Tailgaters”, in I am Charlotte Simmons, New York, N.Y.: Farrar, Straus and Giroux, →ISBN, page 312