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thermostat

thermostat, automatic device that regulates temperature in an enclosed area by controlling heating or refrigerating systems. It is commonly connected to one of these systems, turning it on or off in order to maintain a predetermined temperature. Its operating principle is based on the fact that one of its components expands or contracts significantly during a temperature change. This expansion or contraction actuates a control on a furnace, cooling system, or piece of machinery. The thermostat sometimes uses mercury, which expands when heated and rises in a glass tube until, at a predetermined point, it touches an electrical contact to complete a circuit and thereby actuate a control; conversely, during a lowering of temperature the mercury descends in the tube and breaks the circuit. The thermostat often uses a bimetallic strip, which is made of two thin metallic pieces of different composition that are bonded together. As the temperature of the strip changes, the two pieces change length at different rates, forcing the strip to bend. This bending causes the strip to make or break a circuit.

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thermostat

ther·mo·stat / ˈ[unvoicedth]ərməˌstat/ • n. a device that automatically regulates temperature, or that activates a device when the temperature reaches a certain point. DERIVATIVES: ther·mo·stat·ic / ˌ[unvoicedth]ərməˈstatik/ adj. ther·mo·stat·i·cal·ly / ˌ[unvoicedth]ərməˈstatik(ə)lē/ adv.

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thermostat

thermostat Device for maintaining a constant temperature. A common type contains a strip of two metals, one of which expands and contracts more than the other. At a set temperature, the strip bends and breaks the circuit. As it cools, the strip straightens, makes contact, and the heating begins again once the circuit is complete. Thermostats are used in air-conditioning systems and in refrigerators, ovens and water heaters.

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thermostat

thermostat •Eurocrat • ziggurat • muskrat •theocrat • jurat • Ballarat • democrat •technocrat • bureaucrat • aristocrat •autocrat • plutocrat • babysat •Comsat • Randstad • Darmstadt •diktat • habitat • Eisenstadt •Kronstadt • cryostat • aerostat •aegrotat • rheostat • haemostat •thermostat • photostat

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Thermostat

Thermostat

A thermostat is a device for automatically controlling heating and cooling systems by regulating heat flow into or out of the system. It consists of a circuit controlled by a temperature-sensitive device and connected to the environmental system. Most thermostats use a substance that expands (contracts) when a temperature increase (decrease) occurs.

The most common thermostat, such as the one seen in homes and offices, is based on a bimetallic strip. As its name suggests, a bimetallic strip consists of thin strips of two different metals bonded together. One metal of the strip expands significantly with changes in temperature, the other metal changes very little with temperature increase or decrease. When the temperature increases, for example, one side of the strip will expand more than the other side, causing the strip to bend to one side. When it bends far enough, it closes the circuit, which then directs the air conditioner to turn on. The thermostat adjustment knob varies the distance that the bimetallic strip must bend to close the circuit, allowing selection of temperature level. As the air in the room gets cooler, the metal that expanded with heat will now contract, causing the bimetallic strip to straighten out until it no longer completes the circuit that allows the air conditioner to operate. The air conditioner will turn off until the air becomes warm enough to cause the strip to deform and close the circuit once again.

A number of thermostats, which are variations on this theme, have been developed. Some are based on a brass bellows filled with a thermally sensitive vapor. When the vapor is heated, it expands, pushing out the bellows until it closes the circuit and triggers the heater/air conditioner. Another thermostat design is the bulb type, which includes a bulb and capillary, similar to a thermometer, and a diaphragm. When the bulb is heated, the material expands and travels down the capillary to the diaphragm. The diaphragm in turn moves, moving a lever or spring post and eventually controlling the heating and cooling system.

Electronic (digital) thermostats have become increasingly popular, offering the dual benefits of low cost and minimal moving parts. The active element is a thermistor, a semiconductor device whose resistance to electrical current changes with temperature. Temperature change is signified by a change in measured voltage, which can be used to pass information to the control systems of the heating/cooling units. Electronic thermostats normally are also programmable, which allows the user to customize it for specific needs. Consequently, on average, programmable thermostats provide energy savings over traditional, non-programmable ones.

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Thermostat

Thermostat

A thermostat is a device for controlling heating and cooling systems. It consists of a circuit controlled by a temperature sensitive device and connected to the environmental system. The most common thermostat, such as the one seen in homes and offices, is based on a bimetallic strip. As its name suggests, a bimetallic strip consists of thin strips of two different metals bonded together. One metal of the strip expands significantly with changes in temperature, the other metal changes very little with temperature increase or decrease. When the temperature increases, for example, one side of the strip will expand more than the other side, causing the strip to bend to one side. When it bends far enough, it closes the circuit that directs the air conditioner to turn on. The thermostat adjustment knob varies the distance that the bimetallic strip must bend to close the circuit, allowing selection of temperature level. As the air in the room gets cooler, the metal that expanded with heat will now contract, causing the bimetallic strip to straighten out until it no longer completes the circuit that allows the air conditioner to operate. The air conditioner will turn off until the air becomes warm enough to cause the strip to deform and close the circuit once again.

A number of thermostats that are variations on this theme have been developed. Some are based on a brass bellows filled with a thermally sensitive vapor. When the vapor is heated, it expands, pushing out the bellows until it closes the circuit and triggers the heater/air conditioner. Another thermostat design is the bulb type, which includes a bulb and capillary, similar to a thermometer , and a diaphragm. When the bulb is heated, the material expands and travels down the capillary to the diaphragm. The diaphragm in turn moves, moving a lever or spring post and eventually controlling the heating and cooling system.

Electronic thermostats have become increasingly popular in the past few years, offering the dual benefits of low cost and minimal moving parts. The active element is a thermistor, a semiconductor device whose resistance to electrical current changes with temperature. Temperature change is signified by a change in measured voltage, which can be used to pass information to the control systems of the heating/cooling units.

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"Thermostat." The Gale Encyclopedia of Science. . Retrieved September 22, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/thermostat

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Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

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