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Encyclopedia > Kelvin
Kelvin temperature conversion formulae
from Kelvin to Kelvin
Celsius [℃] = [K] − 273.15 [K] = [℃] + 273.15
Fahrenheit [°F] = [K] × 95 − 459.67 [K] = ([°F] + 459.67) × 59
Rankine [°R] = [K] × 95 [K] = [°R] × 59
For temperature intervals rather than specific temperatures,
1 K = 1 ℃
and
1 K = 1.8 °R
Comparisons among various temperature scales

The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero (0 K). Kelvin can mean The River Kelvin, a river in the Scottish city of Glasgow (from which all other meanings are derived) and additionally: physicist William Thomson, 1st Baron Kelvin (who adopted the name of the river on his enoblement; it flows past the University of Glasgow where Thomson worked). ... For other uses, see Celsius (disambiguation). ... For other uses, see Fahrenheit (disambiguation). ... For the idealized thermodynamic cycle for a steam engine, see Rankine cycle. ... // Comparison of temperature scales ¹ Normal human body temperature is 36. ... The former Weights and Measures office in Middlesex, England. ... For other uses, see Temperature (disambiguation). ... The SI system of units defines seven SI base units: physical units defined by an operational definition. ... Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. ... For other uses, see Absolute Zero (disambiguation). ...


The Kelvin scale and the kelvin are named after the British physicist and engineer William Thomson, 1st Baron Kelvin (1824-1907), who wrote of the need for an “absolute thermometric scale”. For other persons named William Thomson, see William Thomson (disambiguation). ...

Contents

Definition of kelvin

The kelvin unit and its scale, by international agreement, are defined by two points: absolute zero, and the triple point of Vienna Standard Mean Ocean Water (VSMOW).[1] This definition also precisely relates the Kelvin scale to the Celsius scale. Absolute zero—the temperature at which nothing could be colder and no heat energy remains in a substance—is defined as being precisely 0 K and −273.15 °C. The triple point of water is defined as being precisely 273.16 K and 0.01 °C. This definition does three things: The first two pages of the Treaty of Brest-Litovsk, in (left to right) German, Hungarian, Bulgarian, Ottoman Turkish and Russian A treaty is an agreement under international law entered into by actors in international law, namely states and international organizations. ... For other uses, see Absolute Zero (disambiguation). ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ... VSMOW, or Vienna Standard Mean Ocean Water, is an isotopic water standard defined in 1968 by the International Atomic Energy Agency. ... For other uses, see Celsius (disambiguation). ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ...

  1. It fixes the magnitude of the kelvin unit as being precisely 1 part in 273.16 parts the difference between absolute zero and the triple point of water;
  2. It establishes that one kelvin has precisely the same magnitude as a one-degree increment on the Celsius scale; and
  3. It establishes the difference between the two scales’ null points as being precisely 273.15 kelvins (0 K = −273.15 °C and 273.16 K = 0.01 °C). Temperatures in kelvin can be converted to other units per the table at top right.

Temperature equivalents

Kelvin Celsius Fahrenheit
Absolute zero

(precisely, by definition)

0 K −273.15 °C −459.67 °F
Freezing Point of water 273.15 K 0 °C 32 °F
Water’s triple point

(precisely, by definition)

273.16 K 0.01 °C 32.018 °F
Water’s boiling point 373.1339 K 99.9839 °C 211.9710 °F

For Vienna Standard Mean Ocean Water (VSMOW) at one standard atmosphere (101.325 kPa) when calibrated solely per the two-point definition of thermodynamic temperature. Older definitions of the Celsius scale once defined the boiling point of water under one standard atmosphere as being precisely 100 °C. However, the current definition results in a boiling point that is actually 16.1 mK less. For more about the actual boiling point of water, see VSMOW in temperature measurement. For other uses, see Celsius (disambiguation). ... VSMOW, or Vienna Standard Mean Ocean Water, is an isotopic water standard defined in 1968 by the International Atomic Energy Agency. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... VSMOW, or Vienna Standard Mean Ocean Water, is an isotopic water standard defined in 1968 by the International Atomic Energy Agency. ...


SI prefixes

SI multiples for kelvin (K)
Submultiples Multiples
Value Symbol Name Value Symbol Name
10–1 K dK decikelvin 101 K daK decakelvin
10–2 K cK centikelvin 102 K hK hectokelvin
10–3 K mK millikelvin 103 K kK kilokelvin
10–6 K µK microkelvin 106 K MK megakelvin
10–9 K nK nanokelvin 109 K GK gigakelvin
10–12 K pK picokelvin 1012 K TK terakelvin
10–15 K fK femtokelvin 1015 K PK petakelvin
10–18 K aK attokelvin 1018 K EK exakelvin
10–21 K zK zeptokelvin 1021 K ZK zettakelvin
10–24 K yK yoctokelvin 1024 K YK yottakelvin

Typographical and usage conventions

Uppercase/lowercase, plural form usage, and written conventions

When reference is made to the unit kelvin (either a specific temperature or a temperature interval), kelvin is always spelled with a lowercase k unless it is the first word in a sentence.[citation needed] When reference is made to the "Kelvin scale", the word "kelvin"—which is normally a noun—functions adjectivally to modify the noun "scale" and is capitalized. In grammar, an adjective is a word whose main syntactic role is to modify a noun or pronoun (called the adjectives subject), giving more information about what the noun or pronoun refers to. ...


Until the 13th General Conference on Weights and Measures (CGPM) in 1967-1968, the unit kelvin was called a "degree", the same as with the other temperature scales at the time. It was distinguished from the other scales with either the adjective suffix "Kelvin" ("degree Kelvin") or with "absolute" ("degree absolute") and its symbol was °K. Note that the latter (degree absolute), which was the unit’s official name from 1948 until 1954, was rather ambiguous since it could also be interpreted as referring to the Rankine scale. Before the 13th CGPM, the plural forms were "degrees Kelvin" or "degrees absolute". The 13th CGPM changed the name to simply "kelvin" (symbol K).[2] The omission of "degree" indicates that it is not relative to an arbitrary reference point such as the Celsius and Fahrenheit scales, but rather an absolute unit of measure which can be manipulated algebraically (e.g. multiply by 2 to indicate twice the amount of heat). The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, never GCWM). ... For the idealized thermodynamic cycle for a steam engine, see Rankine cycle. ...


Temperatures and intervals

Because the kelvin is an individual unit of measure, it is particularly well-suited for expressing temperature intervals: differences between temperatures or their uncertainties (e.g., “Agar exhibited a melting point hysteresis of 25 kelvins.” and “The uncertainty was 10 millikelvins.”). Of course, the kelvin is also used to express specific temperatures along its scale (e.g. “Gallium melts at 302.9146 kelvin”). Not to be confused with Galium. ...


One disadvantage of the kelvin is that intervals and specific temperatures on the Kelvin scale use exactly the same symbol (e.g., “Agar exhibited a melting point hysteresis of 25 K,” and “The triple point of hydrogen is 13.8033 K”).


Formatting and typestyle for the K symbol

The kelvin symbol is always a roman, non-italic capital K. In the SI naming convention, all symbols named after a person are capitalized; in the case of the kelvin, capitalizing also distinguishes the symbol from the SI prefix “kilo”, which has the lowercase k as its symbol. The admonition against italicizing the symbol K applies to all SI unit symbols; only symbols for variables and constants (e.g. P = pressure, and c = 299,792,458 m/s) are italicized in scientific and engineering papers. As with most other SI unit symbols (angle symbols, e.g. 45° 3′ 4″, are the exception) there is a space between the numeric value and the kelvin symbol (e.g. “99.987 K”).[3][4] Roman type has two separate meanings in typography, both of which refer to the fact that the capital letters of a Roman font have an appearance similar to those used for lettering stone in ancient Rome: Roman type can refer to one of the major families of traditional typefaces as... This article or section does not adequately cite its references or sources. ...


The special Unicode kelvin character

Unicode provides a compatibility character for the kelvin at U+212A (decimal 8490), for compatibility with CJK encodings that provide such a character (as such, in most fonts the width is the same as for fullwidth characters). Below in maroon text is the kelvin character followed immediately by a simple uppercase K: The Unicode Standard, Version 5. ... In discussing Unicode and the UCS, many often refer to compatibility characters. ... In CJK computing, graphic characters are traditionally classed into fullwidth (in Taiwan and Hong Kong: 全形; elsewhere: 全角) and halfwidth (in Taiwan and Hong Kong: 半形; elsewhere: 半角) characters. ...

K K

When viewed on computers that properly support Unicode, the above line may be similar to the line below (size may vary):

The canonical decomposition of this character is U+004B (uppercase K), so some browsers may simply display a "K" in its place due to Unicode normalization. Image File history File links Kelvin_symbol_plus_K.svg‎ A Unicode kelvin symbol and an uppercase K (in that order), rendered in Liberation Sans (in maroon) and converted from text to path in Inkscape. ... Unicode normalization is a form of text normalization that transforms equivalent characters or sequences of characters into a consistent underlying representation so that they may be easily compared. ...


Mixed use of Kelvin and Celsius scales in technical articles

In science and in engineering, the Celsius scale and the kelvin are often used simultaneously in the same article (e.g. “…its measured value was 0.01023 °C with an uncertainty of 70 µK…”). This practice is permissible because the degree Celsius is a special name for the kelvin for use in expressing Celsius temperatures and the magnitude of the degree Celsius is precisely equal to that of the kelvin.[5] Notwithstanding the official endorsement provided by Resolution 3 of the 13th CGPM, states “a temperature interval may also be expressed in degrees Celsius,” the practice of simultaneously using both “°C” and “K” remains widespread throughout the scientific world as the use of SI prefixed forms of the degree Celsius (such as “µ°C” or “microdegrees Celsius”) to express a temperature interval has not been well-adopted.[6] An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ...


Color temperature

The kelvin is often used in the measure of the color temperature of light sources. Color temperature is based upon the principle that a black body radiator emits light whose color depends on the temperature of the radiator. Black bodies with temperatures below about 4000 K appear reddish whereas those above about 7500 K appear bluish. Color temperature is important in the fields of image projection and photography where a color temperature of approximately 5500 K is required to match “daylight” film emulsions. In astronomy, the stellar classification of stars and their place on the Hertzsprung-Russell diagram are based, in part, upon their surface temperature. The Sun, for instance, has an effective photosphere temperature of 5778 K. The CIE 1931 x,y chromaticity space, also showing the chromaticities of black-body light sources of various temperatures, and lines of constant correlated color temperature Color temperature is a characteristic of visible light that has important applications in photography, videography, publishing and other fields. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... Photography [fÓ™tÉ‘grÓ™fi:],[foÊŠtÉ‘grÓ™fi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or electronic sensor. ... For other uses, see Astronomy (disambiguation). ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... The Hertzsprung-Russell diagram (usually referred to by the abbreviation H-R diagram or HRD, also known as a Colour-Magnitude diagram, or CMD) shows the relationship between absolute magnitude, luminosity, classification, and effective temperature of stars. ...


History of the Kelvin scale

Below are some historic milestones in the development of the Kelvin scale and its unit increment, the kelvin. For more on the history of thermodynamic temperature, see Thermodynamic temperature: History of thermodynamic temperature. Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. ...

  • 1848: Lord Kelvin (William Thomson), wrote in his paper, On an Absolute Thermometric Scale, of the need for a scale whereby “infinite cold” (absolute zero) was the scale’s null point, and which used the degree Celsius for its unit increment. Thomson calculated that absolute zero was equivalent to −273 °C on the air thermometers of the time.[7] This absolute scale is known today as the Kelvin thermodynamic temperature scale. It’s noteworthy that Thomson’s value of “−273” was actually derived from 0.00366, which was the accepted expansion coefficient of gas per degree Celsius relative to the ice point. The inverse of −0.00366 expressed to five significant digits is −273.22 °C which is remarkably close to the true value of −273.15 °C.
  • 1954: Resolution 3 of the 10th CGPM gave the Kelvin scale its modern definition by designating the triple point of water as its second defining point and assigned its temperature to precisely “273.16 degrees Kelvin.”[8]
  • 1967/1968: Resolution 3 of the 13th CGPM renamed the unit increment of thermodynamic temperature “kelvin”, symbol K, replacing “degree absolute”, symbol °K.[6] Further, feeling it useful to more explicitly define the magnitude of the unit increment, the 13th CGPM also held in Resolution 4 that “The kelvin, unit of thermodynamic temperature, is equal to the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.”[9]
  • 2005: The Comité International des Poids et Mesures (CIPM), a committee of the CGPM, affirmed that for the purposes of delineating the temperature of the triple point of water, the definition of the Kelvin thermodynamic temperature scale would refer to water having an isotopic composition defined as being precisely equal to the nominal specification of VSMOW water.[1]

For other persons named William Thomson, see William Thomson (disambiguation). ... The International Committee for Weights and Measures is the English name of the Comité international des poids et mesures (CIPM, sometimes written in English Comité International des Poids et Mesures). ... VSMOW, or Vienna Standard Mean Ocean Water, is an isotopic water standard defined in 1968 by the International Atomic Energy Agency. ...

See also

There are very few or no other articles that link to this one. ... For other uses, see Celsius (disambiguation). ... For other uses, see Fahrenheit (disambiguation). ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... The International Temperature Scale of 1990 (ITS-90) is an equipment calibration standard for making measurements on the kelvin and Celsius temperature scales. ... For the idealized thermodynamic cycle for a steam engine, see Rankine cycle. ... Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ...

References

  1. ^ a b Unit of thermodynamic temperature (kelvin). SI Brochure, 8th edition Section 2.1.1.5. Bureau International des Poids et Mesures (1967). Retrieved on 2008-02-06.
  2. ^ Barry N. Taylor (1995). "Guide for the Use of the International System of Units (SI)" (.PDF). Special Publication 811. National Institute of Standards and Technology. Retrieved on 2008-02-06.
  3. ^ SI Unit rules and style conventions. National Institute of Standards and Technology (September 2004). Retrieved on 2008-02-06.
  4. ^ Rules and style conventions for expressing values of quantities. SI Brochure, 8th edition Section 5.3.3. Bureau International des Poids et Mesures (1967). Retrieved on 2008-02-06.
  5. ^ Units with special names and symbols; units that incorporate special names and symbols. SI Brochure, 8th edition Section 2.2.2, Table 3. Bureau International des Poids et Mesures (2006). Retrieved on 2008-02-06.
  6. ^ a b Resolution 3: SI unit of thermodynamic temperature (kelvin). Resolutions of the 13th CGPM. Bureau International des Poids et Mesures (1967). Retrieved on 2008-02-06.
  7. ^ Thomson, William (October 1848). "On an Absolute Thermometric Scale". Philosophical Magazine. Retrieved on 2008-02-06. 
  8. ^ Resolution 3: Definition of the thermodynamic temperature scale. Resolutions of the 10th CGPM. Bureau International des Poids et Mesures (1954). Retrieved on 2008-02-06.
  9. ^ Resolution 4: Definition of the SI unit of thermodynamic temperature (kelvin). Resolutions of the 13th CGPM. Bureau International des Poids et Mesures (1967). Retrieved on 2008-02-06.

Year 1967 (MCMLXVII) was a common year starting on Sunday (link will display full calendar) of the 1967 Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... Year 1967 (MCMLXVII) was a common year starting on Sunday (link will display full calendar) of the 1967 Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... Year 1967 (MCMLXVII) was a common year starting on Sunday (link will display full calendar) of the 1967 Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ... Year 1967 (MCMLXVII) was a common year starting on Sunday (link will display full calendar) of the 1967 Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ...

External links

Look up Kelvin in
Wiktionary, the free dictionary.

for Weights and Measures. Retrieved on 2008-02-06. Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 37th day of the year in the Gregorian calendar. ...

For other uses, see Temperature (disambiguation). ... A scale is either a device used for measurement of weights, or a series of ratios against which different measurements can be compared. ... For other uses, see Celsius (disambiguation). ... For other uses, see Fahrenheit (disambiguation). ... For the idealized thermodynamic cycle for a steam engine, see Rankine cycle. ... The Delisle scale (°D) is a temperature scale invented in 1732 by the French astronomer Joseph-Nicolas Delisle (1688–1768). ... The Leyden temperature scale could plausibly have been introduced around 1894, when Heike Kamerlingh Onnes cryogenic laboratory was established in Leyden, Netherlands. ... Around 1700, Isaac Newton (1642–1727) applied his mind to the problem of heat. ... The degree Réaumur is a unit of temperature named after René Antoine Ferchault de Réaumur, who first proposed it in 1731. ... Rømer is a disused temperature scale named after the Danish astronomer Ole Christensen Rømer, who proposed it in 1701. ... // Ranking to Celsius do not match equations from Celsius table. ...

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