In 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 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, thermal 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. Thermal physics is the combined study of thermodynamics, statistical mechanics, and kinetic theory. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... For other uses, see Temperature (disambiguation). ... HVAC may also stand for High-voltage alternating current HVAC is an initialism that stands for heating, ventilation and air-conditioning. This is sometimes referred to as climate control. ... Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dynamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ... In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... In thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, and chemical equilibrium. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... The second law of thermodynamics is an expression of the universal law of increasing entropy. ...

Internal energy

Internal 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] In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of...

In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... Sensible heat is heat energy that is transported by a body that has a temperature higher than its surroundings via conduction, convection, or both. ... In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... This article concerns the energy stored in the nuclei of atoms; for the use of nuclear fission as a power source, see Nuclear power. ... This article concerns the energy stored in the nuclei of atoms; for the use of nuclear fission as a power source, see Nuclear power. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... In thermal physics, heat transfer is the passage of thermal energy from a hot to a colder body. ... Mass transfer is the phrase commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. ... Look up work in Wiktionary, the free dictionary. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ...

Definitions

System of N particles

According 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] Figure 1. ...

To note, U_thermal 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). In chemistry, bond energy (E) is a measure of bond strength in a chemical bond. ...

Other definitions

Thermal 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 thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... For other uses, see Absolute Zero (disambiguation). ... The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ... HVAC may also stand for High-voltage alternating current HVAC is an initialism that stands for heating, ventilation and air-conditioning. This is sometimes referred to as climate control. ... Heat flow along perfectly insulated wire Conduction is the transfer of heat or electric current from one substance to another by direct contact. ...

In a monatomic ideal gas, the thermal energy is exactly given by the kinetic energy of the constituent particles.^{[citation needed]} In physics and chemistry, monatomic is a combination of the words mono and atomic, and means single atom. ... An ideal gas or perfect gas is a hypothetical gas consisting of identical particles of zero volume, with no intermolecular forces. ...

See also

t In thermodynamics and molecular chemistry, the enthalpy or heat content (denoted as H or ΔH, or rarely as χ) is a quotient or description of thermodynamic potential of a system, which can be used to calculate the useful work obtainable from a closed thermodynamic system under constant pressure. ... For other uses, see: information entropy (in information theory) and entropy (disambiguation). ... In thermal physics, heat transfer is the passage of thermal energy from a hot to a colder body. ... For other uses, see Radiation (disambiguation). ... The thermal efficiency () is a dimensionless performance measure of a thermal device such as an internal combustion engine, a boiler, or a furnace, for example. ... Thermal science is the combined study of thermodynamics, fluid mechanics, and heat transfer. ...

References

1. ^ /eb/article-9072068/thermal-energy Thermal energy - Britannica
2. ^ ^{a b} Schroeder, Daniel, R. (2000). Thermal Physics. New York: Addison Wesley Longman. ISBN 0201380277. 
3. ^ Cengel, Yungus, A.; Boles, Michael (2002). Thermodynamics - An Engineering Approach, 4th ed.. McGraw-Hill, 17-18. ISBN 0-07-238332-1. 
4. ^ Thermal energy – Hyperphysics