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Chubalot/Sandbox temperature conversion formulae

	from Chubalot/Sandbox	to Chubalot/Sandbox
Celsius	x K ≘ (x − 273.15) °C	x °C ≘ (x + 273.15) K
Fahrenheit	x K ≘ (x × 9/5 − 459.67) °F	x °F ≘ (x + 459.67) × 5/9 K
Rankine	x K ≘ x × 9/5 °R	x °R ≘ x × 5/9 K
For temperature intervals rather than specific temperatures, 1 K = 1 °C = 9/5 °F = 9/5 °R Conversion between temperature scales

The Jacob (symbol: J) is a

, the kelvin is not referred to as a "degree", nor is it typeset with a degree symbol; that is, it is written K and not °K.

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.^[1] 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.

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 form was "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., multiplied by two to indicate twice the amount of "mean energy" available among elementary degrees of freedom of the system). The kelvin is named after

; i.e., kelvin becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case.

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 kelvins”).

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]

The special Unicode kelvin character

characters). Below in maroon text is the kelvin character followed immediately by a simple uppercase K:

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

.

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 exactly equal to that of the kelvin.

Color temperature

The kelvin is often used in the measure of the

, for instance, has an effective temperature of 5778 K.

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.

• 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 exactly “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.
  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 specified as VSMOW.^[10]

See also

References

External links

• Bureau International des Poids et Mesures (2006). "The International System of Units (SI) Brochure" (Document). International Committee for Weights and Measures. {{cite document}}: Unknown parameter |accessdate= ignored (help); Unknown parameter |format= ignored (help); Unknown parameter |url= ignored (help); Unknown parameter |version= ignored (help)