rheostat

[ree-uh-stat]
noun Electricity.
an adjustable resistor so constructed that its resistance may be changed without opening the circuit in which it is connected, thereby controlling the current in the circuit.

Origin:
1843; rheo- + -stat

rheostatic, adjective
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World English Dictionary
rheostat (ˈriːəˌstæt)
 
n
a variable resistance, usually consisting of a coil of wire with a terminal at one end and a sliding contact that moves along the coil to tap off the current
 
rheo'static
 
adj

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

rheostat
1843, coined by English physicist Sir Charles Wheatstone (1802-75) from Gk. rheos "a flowing, stream" (from PIE base *sreu-, see rheum) + -stat "regulating device."
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
rheostat   (rē'ə-stāt')  Pronunciation Key 
See under resistor.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

rheostat

adjustable resistor used in applications that require the adjustment of current or the varying of resistance in an electric circuit. The rheostat can adjust generator characteristics, dim lights, and start or control the speed of motors. Its resistance element can be a metal wire or ribbon, carbon, or a conducting liquid, depending on the application. For average currents, the metallic type is most common; for very small currents, the carbon type is used; and for large currents the electrolytic type, in which electrodes are placed in a conducting fluid, is most suitable. A special type of rheostat is the potentiometer, an instrument that measures an unknown voltage or potential difference by balancing it, wholly or in part, by a known potential difference. A more common potentiometer is simply a resistor with two fixed terminals and a third terminal connected to a variable contact arm; it is used for such purposes as a volume control in audio equipment.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Connects battery to battery charger and adjusts rheostat to start flow of electricity into battery.
Employ the lowest rheostat setting on your instrument that shows detail and color to your satisfaction.
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