K-Line

Kelvin is, or relates to, a unit increment of temperature known as the kelvin (symbol: K). The kelvin is the SI unit of temperature and is one of the seven SI base units. more...

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The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero—the lowest possible temperature where nothing could be colder and no heat energy remains in a substance—is defined as being equivalent to zero kelvin (0 K).

“Kelvin” is named after the Irish physicist and engineer William Thomson, 1st Baron Kelvin (1824 – 1907), who wrote of the need for an “absolute thermometric scale.”

Definition of the kelvin

The unit “kelvin” and its scale, by international agreement, are defined by two points: absolute zero, and the triple point of specially prepared (VSMOW) water. 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: 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.

Some key temperatures relating temperatures on the Kelvin and Celsius scales are shown in the table below.

^A For Vienna Standard Mean Ocean Water 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 water in temperature measurement.

SI prefixed forms of kelvin

SI prefixes are often employed to denote decimal multiples and submultiples of the kelvin. The most commonly used factors of kelvin are listed below.

Typographical and usage conventions

Uppercase/lowercase and plural form usage

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. When reference is made to the Kelvin scale, use an uppercase K.

Read more at Wikipedia.org