Kelvin

Related Topics:
Kelvin_Grove

**Formula penukaran suhu Kelvin**
Penukaran dari	kepada	Formula
kelvin	darjah Celsius	°C = K - 273.15
darjah Celsius	kelvins	K = °C + 273.15
kelvins	darjah Fahrenheit	°F = K × 1.8 − 459.67
darjah Fahrenheit	kelvin	K = (°F + 459.67) / 1.8
Perhatikan bahawan untuk selang suhu daripada bacaan-bacaan suhu, 1 K = 1 °C and 1 K = 1.8 °F formula-formula penambahan Conversion calculator for units of temperature

Kelvin (symbol: K) adalah salah satu SI unit suhu, dan ia merupakan satu daripada tujuh unit SIs. Ia ditakrifkan sebagai pecahan /273.16 of the thermodynamic suhu (absolute) titik tiga air.

Satu suhu diberi dalam kelvin, tanpa kualifikasi selanjutnya , diukur kepada sifar mutlak, where molecular motion stops (except for the residual quantum mechanical zero-point energy). It is also common to give a temperature relative to the Celsius temperature scale, with a reference temperature of 0 °C = 273.15 K, approximately the melting point of water under ordinary conditions.

The kelvin is named after the British physicist and engineer William Thomson, 1st Baron Kelvin; his barony was in turn named after the River Kelvin, which runs through the grounds of the University of Glasgow.

Konvensyenn tipografi

Various reasons can be found for why the name “kelvin” is lowercase and its symbol, “K,” is not preceded with a ° (degree) symbol. For instance, some sources say that kelvin has no degree symbol because it has the distinction of being an absolute scale (referencing absolute zero). However, the definition of “degree” is simply “a unit division or step” so it doesn’t matter where a temperature scale’s null point is. Furthermore, the symbol for Rankine (also an absolute scale) is properly preceded by the degree symbol. There are two simple reasons for why the unit name kelvin and its symbol are written as they are: Notwithstanding the naming convention historically used for the other temperature scales, SI unit names are never capitalized. Also, the 13th General Conference on Weights and Measures (CGPM) in 1967 declared that the kelvin symbol, K, would no longer be preceded by a degree symbol because kelvin would no longer refer to the entire scale; it would thereafter be recognized as referring to an individual unit comprising the scale. Thus, the numeric value preceding the unit symbol would simply specify “how many kelvins there are” (just like 15 km or 4 µg). This is why the kelvin is the only unit measure of temperature that may be written in its plural form (e.g. “…is 12 kelvins greater than…”) in the same fashion as with all the other SI units such as mass (e.g. “…is 12 grams greater than…”). Thus, since kelvin has not referred to the entire scale since 1967, it is not appropriate to refer to a degree-related position on it, nor is it proper to precede the “K” with a ° (degree) symbol.

Note that the symbol (not abbreviation) for the unit kelvin is always a capital K (the lowercase version is the SI prefix for 1 x 10³) and is never italicised. As with all other SI units, there is a space between the value and the symbol (e.g. “99.987 K”).

Unicode includes the "kelvin sign" at U+212A (in your browser it looks like K). However, the "kelvin sign" is canonically decomposed into U+004B, thereby seen as a (preexisting) encoding mistake, and it is better to use U+004B (K) directly.

Faktor-faktor penukaran

Kelvins dan Celsius

The Celsius temperature scale is now defined in terms of the kelvin, with 0 °C corresponding to 273.15 kelvins.

kelvins to degrees Celsius

\mathrm{C} = \mathrm{K} - 273.15

Kelvin dan elektronvolt

In some fields, plasma physics in particular, the electronvolt (eV) is used as a unit of 'temperature'. The conversion makes use of k, the Boltzmann constant.

{1 \mbox{ eV} \over k} = {1.6022 \times 10^{-19} \mbox{J} \over 1.380650 \times 10^{-23} \mbox{J/K}} = 11605 \mbox{ K}

Why technical articles use a mix of kelvin and Celsius scales

In science (especially) and in engineering, the Celsius and kelvin scales are often used simultaneously in the same article (e.g. “…its measured value was 0.01023 °C with an uncertainty of 70 µK…”). Because the word “Celsius” refers to the entire scale, and the symbols “°C” refer to a specific step on the scale, values expressed as degrees Celsius are most properly assumed to refer to a specific temperature (e.g. “The melting point of gallium is 29.7646 °C”). In a chart, the value “25 °C” (room temperature) could be confusing if it was actually intended to represent something else like a tolerance.

The symbol “K” on the other hand, is properly used two ways. Because the word “kelvin” officially refers to the individual unit of measure—not the entire scale—it is uniquely suited for expressing differences between temperatures and their uncertainties (e.g. “Agar exhibited a melting point hysteresis of 25 kelvins,” and “The error was 10 millikelvins”). Of course, the kelvin is also used to express specific temperatures along its absolute scale (e.g. “The triple point of hydrogen is 13.8033 kelvin”). Note however, that when referring to a particular temperature on the kelvin scale, the singular form for kelvin (no “s” at the end) is used; when referring to uncertainties and differentials, the plural form is used.

Kelvin’s dual role becomes somewhat obscured when its symbol, “K”, is instead used; there is no plural form. Consequently, differentials, uncertainties, and specific temperatures all utilize the same symbol (e.g. “Agar exhibited a melting point hysteresis of 25 K,” and “The triple point of hydrogen is 13.8033 K”).

In scientific and technical articles, Celsius is not used to express differences between temperatures or their uncertainties. The ° (degree) symbol preceding the “C” has the strong connotation that the value refers to a particular point on the Celsius scale—a particular temperature. Observing this admonition (not a hard rule) avoids the ambiguity. This admonition doesn’t necessarily apply to non-technical articles for the general public where both the kelvin and its symbol, K, would not be well recognized and could be confusing.

Lihat juga

Rujukan

BIPM brochure on the kelvin

Unit-unit asas SI | Unit-unit suhu