Definition of Kelvin

Learn about the definition of Kelvin, its origin, significance, examples, and case studies. Discover why Kelvin is used in scientific and engineering applications.

What is Kelvin?

Kelvin is the unit of thermodynamic temperature used in the International System of Units (SI). It is one of the seven base units in the SI and is named after the Scottish physicist William Thomson, 1st Baron Kelvin.

Origin of Kelvin

The Kelvin scale is named after Lord Kelvin, who proposed it in the 19th century. The Kelvin scale starts at absolute zero, the theoretical temperature at which all molecular motion ceases.

How Kelvin is Defined

One Kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The triple point of water is the temperature at which water can coexist in solid, liquid, and gaseous states.

Why Kelvin is Used

Kelvin is used in scientific and engineering applications where precise temperature measurements are required. It is particularly useful in thermodynamics, astronomy, and physics.

Examples of Kelvin

  • 0 Kelvin: Absolute zero, the lowest temperature possible
  • 273.15 Kelvin: The triple point of water
  • 300 Kelvin: Room temperature

Case Studies

In astronomy, the Kelvin scale is used to measure the temperature of stars and other celestial bodies. In thermodynamics, Kelvin is used to calculate the efficiency of heat engines. In physics, Kelvin is used in the study of phase transitions in materials.


In scientific research, Kelvin is the preferred unit of temperature measurement due to its absolute nature. It provides a common reference point for comparing temperatures across different systems and experiments.

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