Name: how thermometers measure heat
Uploaded: 2023-04-30T12:29:09.000Z
Duration: 1 min 22 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.13

CHEM.13.D

Thermometers and Temperature Scales

Un thermomètre est un appareil utilisé pour mesurer la température d’un corps ou d’un objet.
Certains des types de thermomètres les plus importants sont les thermomètres à liquide dans verre, bimétalliques, numériques, infrarouges et à gaz.
Les thermomètres mesurent la température sur trois échelles principales : Celsius, Fahrenheit et Kelvin. Ces échelles ont été conçues en fonction des points de congélation et d’ébullition de l’eau.
Sur l’échelle de température Celsius, le point de congélation de l’eau est étiqueté comme zéro, tandis que le point d’ébullition de l’eau est étiqueté comme cent. Il y a des intervalles de cent degrés entre ces deux points, c’est pourquoi elle est également connue sous le nom d’échelle centigrade.
Ici, l’unité de température est le degré Celsius.
Sur l’échelle de température Fahrenheit, le point de congélation de l’eau est indiqué à 32, tandis que le point d’ébullition est de 212. L’unité de température sur cette échelle est le degré Fahrenheit.
La température sur l’échelle Fahrenheit peut facilement être convertie en degrés Celsius en utilisant l’équation de conversion.
L’échelle de température Kelvin est une échelle de température absolue. Ici, zéro kelvin indique le zéro absolu, qui est la température la plus basse possible.

<ol>
	<li>OpenStax. (2019). Physique universitaire Vol. 2. [Version Web]. Récupéré de <a href="https://openstax.org/books/university-physics-volume-2/pages/1-2-thermometers-and-temperature-scales">https://openstax.org/books/university-physics-volume-2/pages/1-2-thermometers-and-temperature-scales</a></li>
</ol>

thermomètres et échelles de température

Toute propriété physique qui dépend de manière cohérente et reproductible de la température peut être utilisée comme base d'un thermomètre. Par exemple, le volume augmente avec la température pour la plupart des substances. Cette propriété est la base du thermomètre à alcool courant et des thermomètres à mercure d'origine. D'autres propriétés utilisées pour mesurer la température comprennent la résistance électrique, la couleur et l'émission de rayonnement infrarouge.

Étant donné que de nombreuses propriétés physiques dépendent de la température, la variété des thermomètres est remarquable. Dans le type le plus courant de thermomètre, l'alcool, contenant un colorant rouge, se dilate plus rapidement que le verre qui l'entoure. Lorsque la température du thermomètre augmente, le liquide provenant de l'ampoule est forcé dans un tube étroit, produisant un grand changement de la longueur de la colonne pour un petit changement de température. Un autre type courant de thermomètre est le pyromètre. Un pyromètre mesure le rayonnement infrarouge (dont l'émission varie avec la température) de la source et affiche rapidement une lecture de température. Les thermomètres infrarouges sont également fréquemment utilisés pour mesurer la température corporelle en les plaçant délicatement dans le conduit auditif. Ces thermomètres sont plus précis que les thermomètres à alcool placés sous la langue ou sous l'aisselle.

Les thermomètres mesurent la température selon des échelles de mesure bien définies. Les trois échelles de température les plus courantes sont Fahrenheit, Celsius et Kelvin. Les échelles de température sont créées en identifiant deux températures reproductibles, le plus souvent les températures de gel et d'ébullition de l'eau à pression atmosphérique standard.

Thermomètres et échelles de température

Toute propriété physique qui dépend de manière constante et reproductible de la température peut être utilisée comme base d’un thermomètre. Par exemple, le volume augmente...

Education

Enseignement

JoVE Core

Physics

Physique

Unit 1

Unité 1

Temperature and Heat

Température et chaleur

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

how thermometers measure heat

Thermometers measure temperature by using physical properties that change in a predictable way. One common example is volume. For most substances, volume increases as temperature rises. That idea is used in alcohol thermometers and in the original mercury thermometers.

Other thermometer designs use different temperature-sensitive properties. Some measure electrical resistance, color, or the emission of infrared radiation. The alcohol thermometer is a common example. It contains red-dyed alcohol that expands faster than the glass around it. As the liquid warms, it moves from the bulb into a narrow tube. That creates a large change in the length of the liquid column for a small temperature change.

A pyrometer is another type of thermometer. It measures infrared radiation from a source, and its output changes with temperature. It can give a temperature readout very quickly. Infrared thermometers are also used to measure body temperature in the ear canal. They are more accurate than alcohol thermometers used under the tongue or under the armpit.

Thermometers use temperature scales to turn measurements into numbers. The three most common scales are Fahrenheit, Celsius, and Kelvin. These scales are built from two reproducible temperatures. The freezing and boiling points of water at standard atmospheric pressure are the most common reference points.

How Thermometers Measure Heat

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Heat and temperature are key ideas in thermodynamics and in everyday life. People often connect temperature with hot and cold, but science gives it a more precise meaning. Temperature is the quantity measured with a thermometer. It is also linked to the average translational kinetic energy of particles. Heat is different from temperature. Heat is energy that moves from one place or material to another because there is a difference in temperature. That difference in temperature keeps heat...

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thermometers and temperature scales

Thermometers measure temperature by using physical properties that change in a predictable way. One common example is volume. For most substances, volume increases as temperature rises. That idea is used in alcohol thermometers and in the original mercury thermometers. Other thermometer designs use different temperature-sensitive properties. Some measure electrical resistance, color, or the emission of infrared radiation. The alcohol thermometer is a common example. It contains red-dyed...

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Heat transfer happens when there is a temperature difference. It can move fast, like through a cooking pan, or slowly, like through the walls of a picnic ice box. Heat transfer appears in many everyday situations, so it is hard to find a place where it does not occur. There are only three ways heat is transferred: conduction, convection, and radiation. A fireplace shows all three at once. Radiation carries most of the heat into the room. Conduction also moves heat into the room, but much more...

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Convection and radiation are two major ways heat moves. In convection, thermal energy is carried by the large-scale flow of matter. Warm air and water rise because they are less dense, so ocean currents and large-scale atmospheric circulation move heat from the tropics toward the poles and move cold air from the poles toward the tropics. Earth’s rotation changes these moving air currents. It interacts with the flow and helps produce the eastward movement of air in the temperate zones.

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Earth’s Energy Balance and Greenhouse Effect

Earth’s energy balance and the greenhouse effect help explain its average temperature. Earth is in radiative contact with both the Sun and dark space. It receives almost all of its energy from solar radiation, and it reflects some of that energy back into outer space. Dark space is very cold, about 3 K, so Earth also radiates energy into it. Heat can move quickly from soil and grasses, and frost can form on clear summer evenings, even in warm latitudes. In a first approximation, Earth’s...

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Radiation Heat Transfer and Thermographs

Radiation heat transfer depends on temperature, surface area, and emissivity. The Stefan-Boltzmann law describes the rate of heat transfer by emitted radiation. In this law, σ is the Stefan-Boltzmann constant, A is the object’s surface area, and T is its temperature in kelvins. The fourth-power dependence on absolute temperature makes radiation highly sensitive to small temperature changes. Even a slight rise in temperature can change the emitted heat a lot. That sensitivity is why radiation...

key terms and concepts

See how thermometers use expansion, infrared radiation, and other temperature-sensitive properties to measure temperature on Fahrenheit, Celsius, and Kelvin scales.

How Thermometers Measure Heat | JoVE K12

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How Thermometers Measure Heat

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