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Thermal energyIn thermal physics, thermal energy is the energy portion of a system that increases with its temperature. In a loose sense, "thermal energy" is a term often used to describe the energy content of a system related to heating effects, e.g. temperature increase or decrease. In thermodynamics, thermal energy is the internal energy present in a system in a state of thermodynamic equilibrium by virtue of its temperature.[1] The term is not widely used, however, in a rigorous sense, owing to the result that the phrase "thermal (heat) energy" is counter-intuitive. That is, heat can only be defined as any spontaneous flow of energy (energy in transit) from one object to another, caused by a difference in temperature between two objects; thus, an object cannot possess "heat".[2] This is explained by the second law of thermodynamics. Hence, by extrapolation, it is difficult to define quantities of heat energy (thermal energy). In isolated cases, however, a few definitions do exist. Additional recommended knowledge
Internal energyInternal energy – the sum of all microscopic forms of energy of a system. It is related to the molecular structure and the degree of molecular activity and may be viewed as the sum of kinetic and potential energies of the molecules; it consists of the following types of energies:[3]
DefinitionsSystem of N particlesAccording to the equipartition theorem, it is possible to define thermal energy. In a system of N molecules, each with f degrees of freedom, and if there are no other (non-quadratic) temperature-dependent forms of energy, then the total thermal energy of the system is:[2] To note, Uthermal is almost never the total energy of a system; for instance, there can be static energy that doesn't change with temperature, such as bond energy or rest energy (E=mc2). Other definitionsThermal energy per particle is also called the average translational kinetic energy possessed by free particles given by equipartition of energy.[4] Thermal energy is the difference between the internal energy of an object and the amount that it would have at absolute zero.[citation needed] It includes the quantity of kinetic energy due to the motion of the internal particles of an object, and is increased by heating and reduced by cooling. In a monatomic ideal gas, the thermal energy is exactly given by the kinetic energy of the constituent particles.[citation needed] See also
References
Categories: Thermodynamics | Heat |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Thermal_energy". A list of authors is available in Wikipedia. |