Thermal energy

Thermal energy is a term sometimes used loosely as a synonym for more rigorous thermodynamic quantities such as the (entire) internal energy of a system; or for heat or sensible heat which are defined as types of transfer of energy (just as work is another type of transfer of energy), or for the characteristic energy of a degree of freedom in a thermal system $kT$ , where $T$ is temperature and $k$ is the Boltzmann constant. Heat and work depend on the way in which an energy transfer occurred, whereas internal energy is a property of the state of a system and can thus be understood even without knowing how the energy got there.

Relation to heat and internal energy[edit]

Heat is energy transferred spontaneously from a hotter to a colder system or body.^[1]^[2] Heat is energy in transfer, not a property of the system; it is not 'contained' within the boundary of the system.^[1] On the other hand, internal energy is a property of a system. In an ideal gas, the internal energy is the statistical mean of the kinetic energy of the gas particles, and it is this kinetic motion that is the source and the effect of the transfer of heat across a system boundary. For this reason, the term "thermal energy" is sometimes used synonymously with internal energy. The term "thermal energy" is also applied to the energy carried by a heat flow.^[3]

In many statistical physics texts, "thermal energy" refers to the product of Boltzmann's constant and the absolute temperature, typically written $kT$ or $k_{B}T$ .^[4] See the article kT (energy) for more details.

Historical context[edit]

In an 1847 lecture entitled "On Matter, Living Force, and Heat," James Prescott Joule characterised various terms that are closely related to thermal energy and heat. He identified the terms latent heat and sensible heat as forms of heat each affecting distinct physical phenomena, namely the potential and kinetic energy of particles, respectively.^[5] He described latent energy as the energy of interaction in a given configuration of particles, i.e. a form of potential energy, and the sensible heat as an energy affecting temperature measured by the thermometer due to the thermal energy, which he called the living force.

Useless thermal energy[edit]

If the minimum temperature of a system's environment is $T_{e}$ and the system's entropy is $S$ , then a part of the system's internal energy amounting to $S\cdot T_{e}$ cannot be converted into useful work. This is the difference between the internal energy and the Helmholtz free energy.

References[edit]

↑ ^1.0 ^1.1 Robert F. Speyer (2012). Thermal Analysis of Materials. Materials Engineering. Marcel Dekker, Inc. p. 2. ISBN 0-8247-8963-6. Search this book on
↑ Thomas W. Leland, Jr., G. A. Mansoori, ed., Basic Principles of Classical and Statistical Thermodynamics (PDF)
↑ Ashcroft, Neil; Mermin, N. David (1976). Solid State Physics. Harcourt. p. 20. ISBN 0-03-083993-9. We define the thermal current density ${\bf {j}}^{q}$ to be a vector parallel to the direction of heat flow, whose magnitude gives the thermal energy per unit time crossing a unit area perpendicular to the flow. Search this book on
↑ Reichl, Linda E. (2016). A Modern Course in Statistical Physics. John Wiley and Sons. p. 154. ISBN 9783527690466. Search this book on
Kardar, Mehran (2007). Statistical Physics of Particles. Cambridge University Press. p. 243. ISBN 9781139464871. Search this book on
Feynman, Richard P. (2000). "The Computing Machines in the Future". Selected Papers of Richard Feynman: With Commentary. World Scientific. ISBN 9789810241315. Search this book on
Feynman, Richard P. (2018). Statistical Mechanics: A Set of Lectures. CRC Press. p. 265. ISBN 9780429972669. Search this book on
Kittel, Charles (2012). Elementary Statistical Physics. Courier Corporation. p. 60. ISBN 9780486138909. Search this book on
↑ J. P. Joule (1884), "Matter, Living Force, and Heat", The Scientific Papers of James Prescott Joule, The Physical Society of London, p. 274, retrieved 2 January 2013, I am inclined to believe that both of these hypotheses will be found to hold good,—that in some instances, particularly in the case of sensible heat, or such as is indicated by the thermometer, heat will be found to consist in the living force of the particles of the bodies in which it is induced; whilst in others, particularly in the case of latent heat, the phenomena are produced by the separation of particle from particle, so as to cause them to attract one another through a greater space.

This article "Thermal energy" is from Wikipedia. The list of its authors can be seen in its historical and/or the page Edithistory:Thermal energy. Articles copied from Draft Namespace on Wikipedia could be seen on the Draft Namespace of Wikipedia and not main one.

This page exists already on Wikipedia.

[speyer-1] 1.0 ^1.1 Robert F. Speyer (2012). Thermal Analysis of Materials. Materials Engineering. Marcel Dekker, Inc. p. 2. ISBN 0-8247-8963-6. Search this book on

[leland-2] Thomas W. Leland, Jr., G. A. Mansoori, ed., Basic Principles of Classical and Statistical Thermodynamics (PDF)

[3] Ashcroft, Neil; Mermin, N. David (1976). Solid State Physics. Harcourt. p. 20. ISBN 0-03-083993-9. We define the thermal current density ${\bf {j}}^{q}$ to be a vector parallel to the direction of heat flow, whose magnitude gives the thermal energy per unit time crossing a unit area perpendicular to the flow. Search this book on

[4] Reichl, Linda E. (2016). A Modern Course in Statistical Physics. John Wiley and Sons. p. 154. ISBN 9783527690466. Search this book on
Kardar, Mehran (2007). Statistical Physics of Particles. Cambridge University Press. p. 243. ISBN 9781139464871. Search this book on
Feynman, Richard P. (2000). "The Computing Machines in the Future". Selected Papers of Richard Feynman: With Commentary. World Scientific. ISBN 9789810241315. Search this book on
Feynman, Richard P. (2018). Statistical Mechanics: A Set of Lectures. CRC Press. p. 265. ISBN 9780429972669. Search this book on
Kittel, Charles (2012). Elementary Statistical Physics. Courier Corporation. p. 60. ISBN 9780486138909. Search this book on

[5] J. P. Joule (1884), "Matter, Living Force, and Heat", The Scientific Papers of James Prescott Joule, The Physical Society of London, p. 274, retrieved 2 January 2013, I am inclined to believe that both of these hypotheses will be found to hold good,—that in some instances, particularly in the case of sensible heat, or such as is indicated by the thermometer, heat will be found to consist in the living force of the particles of the bodies in which it is induced; whilst in others, particularly in the case of latent heat, the phenomena are produced by the separation of particle from particle, so as to cause them to attract one another through a greater space.

[1]

[2]

[3]

[4]

[5]

v t e Energy
Fundamental concepts	Outline of energy Energy Units Conservation of energy Energetics Energy transformation Energy condition Energy transition Energy level Energy system Mass Negative mass Mass–energy equivalence Power Thermodynamics Quantum thermodynamics Laws of thermodynamics Thermodynamic system Thermodynamic state Thermodynamic potential Thermodynamic free energy Irreversible process Thermal reservoir Heat transfer Heat capacity Volume (thermodynamics) Thermodynamic equilibrium Thermal equilibrium Thermodynamic temperature Isolated system Entropy Free entropy Entropic force Negentropy Work Exergy Enthalpy
Types	Kinetic Internal Thermal Potential Gravitational Elastic Electrical potential energy Mechanical Interatomic potential Electrical Magnetic Ionization Radiant Binding Nuclear binding energy Gravitational binding energy Chromodynamic Dark Quintessence Phantom Negative Chemical Rest Sound energy Surface energy Mechanical wave Sound wave Vacuum energy Zero-point energy
Energy carriers	Radiation Enthalpy Fuel fossil fuel Heat Latent heat Work Electricity Battery Capacitor
Primary energy	Fossil fuel Coal Petroleum Natural gas Gravitational energy Nuclear fuel Natural uranium Radiant energy Solar Wind Bioenergy Geothermal Hydropower Marine energy
Energy system components	Energy engineering Oil refinery Fossil-fuel power station Cogeneration Integrated gasification combined cycle Electric power Nuclear power Nuclear power plant Radioisotope thermoelectric generator Solar power Photovoltaic system Concentrated solar power Solar thermal energy Solar power tower Solar furnace Wind power Wind farm High-altitude wind power Geothermal power Hydropower Hydroelectricity Wave farm Tidal power Biomass
Use and supply	Energy consumption Energy storage World energy consumption Energy security Energy conservation Efficient energy use Transport Agriculture Renewable energy Sustainable energy Energy policy Energy development Worldwide energy supply South America USA Mexico Canada Europe Asia Africa Australia
Misc.	Jevons's paradox Carbon footprint

Thermal energy

Contents

Relation to heat and internal energy[edit]

Historical context[edit]

Useless thermal energy[edit]

See also[edit]

References[edit]