In mechanics the sum of
potential energy and
kinetic energy. In thermodynamics the
internal energy or
thermodynamic energy increase,
, is the sum of
heat and
work brought to the system. Only changes in energy are measurable. For photons
where
is the
Planck constant
and
the frequency of radiation.
In relativistic physics
where
is the speed of light
and
the mass.
Source:
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.
