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Internal Energy

Internal energy refers to the sum total of kinetic energy due to molecular motion (either translational, rotational, or vibrational) in a system with defined boundaries, as well as the potential energy associated with vibrational and electric energy of all atoms contained within molecules or crystals. Internal energy also includes chemical bond energy and free electron energy in metals.

Energy not included in the internal energy measurement are: rotational and translational kinetic energy of the system when taken as a whole (for instance, that of a planet as opposed to the atoms that make up the planet), the relativistic mass-to-energy equivalent, or the potential energy due to an external gravitational or electrostatic field.

The first law of thermodynamics defines the energy of the system, and states that within the system all energy is conserved; if one portion of the system loses energy, another portion of the system gains energy. Internal energy can never be precisely measured. Its truest measurement is the amount of energy that must be removed from the system to bring it to absolute zero.

Web Resources On Internal Energy

Internal Energy
Work, Heat and Internal Energy

Book Resources On Internal Energy

Diurnal variation of kinetic and internal energy in onshore winds along the upper Texas gulf coast by Tsann-wang Yu
Pressure dependence of the internal energy of nitrogen at constant temperature by William Thomas Burgess

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