Knowra Kelvin scale Kelvin scale The Kelvin scale is an absolute temperature scale whose zero is absolute zero and whose increments equal the size of Celsius degrees. Its unit, the kelvin, is named for William Thomson, Lord Kelvin.
Absolute zero : The lowest possible thermodynamic temperature, at which a system has minimum thermal energy. It defines the scale’s zero point.
Kelvin : The SI base unit of thermodynamic temperature, symbolized by K. It is the unit used for values on the Kelvin scale.
William Thomson, 1st Baron Kelvin : A nineteenth-century physicist and engineer who formulated an absolute temperature scale and later became Lord Kelvin. His work supplied the scale’s original conception and name.
Black-body radiation : Electromagnetic radiation emitted by an ideal absorber whose spectrum depends on its temperature. Its spectrum is described using absolute temperature in kelvins.
Celsius scale : A temperature scale that assigns 0 °C to water’s freezing point and 100 °C to its boiling point at standard pressure. Kelvin and Celsius use equal-sized increments but different zero points.
Boltzmann constant : A physical constant relating temperature to energy, with exact SI value 1.380649 × 10⁻²³ joules per kelvin. Its fixed value defines the kelvin in the modern SI.
James Prescott Joule : A British physicist whose experiments established the equivalence of mechanical work and heat. His work on heat and energy informed Thomson’s thermodynamic temperature theory.
Ideal gas law : The equation relating pressure, volume, amount, and temperature of an ideal gas: PV = nRT. The equation requires absolute temperature, normally expressed in kelvins.
Thermodynamic temperature : Temperature defined by thermodynamic principles rather than by a particular material or thermometer. The Kelvin scale gives thermodynamic temperature a unit and absolute origin.
Triple point of water : The unique temperature and pressure at which water’s solid, liquid, and vapor phases coexist in equilibrium. It was the defining fixed point for the kelvin before the 2019 SI revision.
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