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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.^[1][2] In thermodynamics, the quantity TdS is used as a representative measure of heat, which is the absolute temperature of an object multiplied by the differential quantity of a system's entropy measured at the boundary of the object. Heat can flow spontaneously from an object with a high temperature to an object with a lower temperature. The transfer of heat from an object, to another object with an equal or higher temperature, however, can happen only with the aid of a heat pump. High temperature bodies, which often result in high rates of heat transfer, can be created by chemical reactions (such as burning), nuclear reactions (such as fusion taking place inside the Sun), electromagnetic dissipation (as in electric stoves), or mechanical dissipation (such as friction). Heat can be transferred between objects by radiation, conduction and convection. Temperature is used as a measure of the internal energy or enthalpy, that is the level of elementary motion giving rise to heat transfer. Heat can only be transferred between objects, or areas within an object, with different temperatures (as given by the zeroth law of thermodynamics), and then, in the absence of work, only in the direction of the colder body (as per the second law of thermodynamics). The temperature and phase of a substance subject to heat transfer are determined by latent heat and heat capacity. A related term is thermal energy, loosely defined as the energy of a body that increases with its temperature. Image File history File links Crystal_128_energy. ... Look up heat in Wiktionary, the free dictionary. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... 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). ... 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. ... Absolute zero is the lowest temperature that can be obtained in any macroscopic system. ... For a less technical and generally accessible introduction to the topic, see Introduction to entropy. ... In thermodynamics, a boundary is a real or imaginary volumetric demarcation region drawn around a thermodynamic system across which quantities such as heat, mass, or work can flow. ... A diagram of a simple heat pumps vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor. ... In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. ... For other uses, see Chemical reaction (disambiguation). ... A combustion reaction taking place in a igniting match Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. ... In nuclear physics, a nuclear reaction is a process in which two nuclei or nuclear particles collide to produce products different from the initial particles. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Sol redirects here. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... A wave that loses amplitude is said to dissipate. ... A stove is a heat-producing device. ... For other uses, see Mechanic (disambiguation). ... For other uses, see Friction (disambiguation). ... “Radiant heat” redirects here. ... Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences. ... Convection in the most general terms refers to the internal movement of currents within fluids (i. ... For other uses, see Temperature (disambiguation). ... 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. ... The zeroth law of thermodynamics may be succintly stated as: If two thermodynamic systems A and B are in thermal equilibrium, and B and C are also in thermal equilibrium, then A and C are in thermal equilibrium. ... The second law of thermodynamics is an expression of the universal law of increasing entropy. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In thermal physics, thermal energy is the energy portion of a system that increases with its temperature. ... For other uses, see Temperature (disambiguation). ...

Heat from the sun is the driving force of life. The science of heat and its relation to work is thermodynamics. Heat flow can be created many ways.

Image File history File links Size of this preview: 800 × 562 pixel Image in higher resolution (1014 × 712 pixel, file size: 497 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Sun ... Image File history File links Size of this preview: 800 × 562 pixel Image in higher resolution (1014 × 712 pixel, file size: 497 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Sun ... Sol redirects here. ... its made by jaypeeng magandang google wikepedia For other uses, see Force (disambiguation). ... For other uses, see Life (disambiguation). ... Part of a scientific laboratory at the University of Cologne. ... Look up work in Wiktionary, the free dictionary. ... 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. ... This article is in the process of being merged into Heat, and may be outdated. ...

[edit] Overview

The first law of thermodynamics states that the energy of a closed system is conserved. Therefore, to change the energy of a system, energy must be transferred to or from the system. Heat and work are the only two mechanisms by which energy can be transferred to or from a control mass. Heat is the transfer of energy caused by the temperature difference. The unit for the amount of energy transferred by heat in International System of Units SI is the Joule, though the British Thermal Unit and the calorie are still occasionally used in the United States. The unit for the rate of heat transfer is the Watt (J/s). The first law of thermodynamics, a generalized expression of the law of the conservation of energy, states: // Description Essentially, the First Law of Thermodynamics declares that energy is conserved for a closed system, with heat and work being the forms of energy transfer. ... In thermodynamics, a closed system, as contrasted with an isolated system, can exchange heat and work, but not matter, with its surroundings. ... SI derived units are part of the SI system of measurement units and are derived from the seven SI base units. ... The joule (IPA: or ) (symbol: J) is the SI unit of energy. ... The British thermal unit (BTU or Btu) is a unit of energy used in the Power, Steam Generation and Heating and Air Conditioning industry globally. ... A calorie is a unit of measurement for energy. ... For other uses, see Watt (disambiguation). ...

Heat Q can flow across the boundary of the system and thus change its internal energy U.

Heat transfer is a path function (process quantity), as opposed to a point function (state quantity). Heat flows between systems that are not in thermal equilibrium with each other; it spontaneously flows from the areas of high temperature to areas of low temperature. When two bodies of different temperature come into thermal contact, they will exchange internal energy until their temperatures are equalized; that is, until they reach thermal equilibrium. The adjective hot is used as a relative term to compare the object’s temperature to that of the surroundings (or that of the person using the term). The term heat is used to describe the flow of energy. In the absence of work interactions, the heat that is transferred to an object ends up getting stored in the object in the form of internal energy. Image File history File links Download high resolution version (931x818, 88 KB) Summary Creator: Libb Thims (user:wavesmikey) Date Created: 11/29/05 URL: http://www. ... Image File history File links Download high resolution version (931x818, 88 KB) Summary Creator: Libb Thims (user:wavesmikey) Date Created: 11/29/05 URL: http://www. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... 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... A process quantity (or a process function) is a physical quantity that describes the transition of a system from an equilibrium state to another equilibrium state. ... A state quantity (or a state function) is a physical quantity that describes the equilibrium state of a system. ... For other uses, see Temperature (disambiguation). ... In thermodynamics, a thermodynamic system is in thermodynamic equilibrium if its energy distribution equals a Maxwell-Boltzmann-distribution. ...

A red-hot iron rod from which heat transfer to the surrounding environment will be primarily through radiation.

Specific heat is defined as the amount of energy that has to be transferred to or from one unit of mass or mole of a substance to change its temperature by one degree. Specific heat is a property, which means that it depends on the substance under consideration and its state as specified by its properties. Fuels, when burned, release much of the energy in the chemical bonds of their molecules. Upon changing from one phase to another, a pure substance releases or absorbs heat without its temperature changing. The amount of heat transfer during a phase change is known as latent heat and depends primarily on the substance and its state. Download high resolution version (1600x1163, 240 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (1600x1163, 240 KB) Wikipedia does not have an article with this exact name. ... In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ... The specific heat capacity (symbol c or s, also called specific heat) of a substance is defined as heat capacity per unit mass. ... This article or section is in need of attention from an expert on the subject. ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... This article describes degree as a unit of temperature. ... For other uses, see Fuel (disambiguation). ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ...

[edit] Thermal energy

See main article: Thermal energy

Thermal energy is a term often confused with that of heat. Loosely speaking, when heat is added to a thermodynamic system its thermal energy increases and when heat is withdrawn its thermal energy decreases. In this point of view, objects that are hot are referred to as being in possession of a large amount of thermal energy, whereas cold objects possess little thermal energy. Thermal energy then is often mistakenly defined as being synonym for the word heat. This, however, is not the case: an object cannot possess heat, but only energy. The term thermal energy when used in conversation is often not used in a strictly correct sense, but is more likely to be only used as a descriptive word. In physics and thermodynamics, the words “heat”, “internal energy”, “work”, "enthalpy" (heat content), "entropy", "external forces", etc., which can be defined exactly, i.e. without recourse to internal atomic motions and vibrations, tend to be preferred and used more often than the term thermal energy, which is difficult to define. In thermal physics, thermal energy is the energy portion of a system that increases with its temperature. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... 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, work is the quantity of energy transferred from one system to another without an accompanying transfer of entropy. ... 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 a less technical and generally accessible introduction to the topic, see Introduction to entropy. ... its made by jaypeeng magandang google wikepedia For other uses, see Force (disambiguation). ...

[edit] History

Main article: history of heat; see also: heat and affinity.

In the history of science, the history of heat traces its origins from the first hominids to make fire and to speculate on its operation and meaning to modern day particle physicists who study the sub-atomic nature of heat. In short, the phenomenon of heat and its definition evolved from mythological theories of fire, to heat, to terra pinguis, phlogiston, to fire air, to caloric, to the theory of heat, to the mechanical equivalent of heat, to thermo-dynamics (sometimes called energetics) to thermodynamics. The history of heat, then, is a precursor for developments and theories in the history of thermodynamics. In the history of science, the history of heat traces its origins to the first hominids to make fire and to speculate on its operation and meaning to modern day particle physicists who study the sub-atomic nature of heat. ... Over the course of over two-thousand years the theory of what specifically heat was and how this related to affinity, i. ... Science is a body of empirical, theoretical, and practical knowledge about the natural world, produced by a global community of researchers making use of a body of techniques known as scientific methods, emphasizing the observation, experimentation and scientific explanation of real world phenomena. ... Genera Subfamily Ponginae Pongo - Orangutans Gigantopithecus (extinct) Sivapithecus (extinct) Subfamily Homininae Gorilla - Gorillas Pan - Chimpanzees Homo - Humans Paranthropus (extinct) Australopithecus (extinct) Sahelanthropus (extinct) Ardipithecus (extinct) Kenyanthropus (extinct) Pierolapithecus (extinct) (tentative) The Hominids (Hominidae) are a biological family which includes humans, extinct species of humanlike creatures and the other great apes... For other uses, see Fire (disambiguation). ... Particle physics is a branch of physics that studies the elementary constituents of matter and radiation, and the interactions between them. ... For other uses, see Fire (disambiguation). ... Over the course of over two-thousand years the theory of what specifically heat was and how this related to affinity, i. ... The phlogiston theory is a now discredited 17th century hypothesis regarding combustion. ... In the history of chemistry, fire air was postulated to be one of two fluids of common air. ... While phlogiston theory was widely accepted, phlogiston was thought to be the matter of heat. ... In the history of science, the theory of heat was a term used during the 18th and 19th centuries to describe a number of laws, relations, and experimental phenomenon in relation to heat; those such as thermometry, calorimetry, combustion, specific heat, and discussions as to the quantity of heat released... Conservation of energy also known as the first law of thermodynamics is possibly the most important, and certainly the most practically useful, of several conservation laws in physics. ... Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dunamis, 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. ... Energetics is the scientific study of energy flows under transformation. ... 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. ... The 1698 Savery Engine - the worlds first engine built by Thomas Savery as based on the designs of Denis Papin. ...

[edit] Notation

The total amount of energy transferred through heat transfer is conventionally abbreviated as Q. The conventional sign convention is that when a body releases heat into its surroundings, Q < 0 (-); when a body absorbs heat from its surroundings, Q > 0 (+). Heat transfer rate, or heat flow per unit time, is denoted by:

.

It is measured in watts. Heat flux is defined as rate of heat transfer per unit cross-sectional area, and is denoted q, resulting in units of watts per square metre, though slightly different notation conventions can be used. For other uses, see Watt (disambiguation). ...

[edit] Entropy

In 1854, German physicist Rudolf Clausius defined the second fundamental theorem (the second law of thermodynamics) in the mechanical theory of heat (thermodynamics): "if two transformations which, without necessitating any other permanent change, can mutually replace one another, be called equivalent, then the generations of the quantity of heat Q from work at the temperature T, has the equivalence-value:"^[3][4] Rudolf Clausius - physicist and mathematician Rudolf Julius Emanuel Clausius (January 2, 1822 – August 24, 1888), was a German physicist and mathematician. ... The second law of thermodynamics is an expression of the universal law of increasing entropy. ... In the history of science, the theory of heat was a term used during the 18th and 19th centuries to describe a number of laws, relations, and experimental phenomenon in relation to heat; those such as thermometry, calorimetry, combustion, specific heat, and discussions as to the quantity of heat released... 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, work is the quantity of energy transferred from one system to another without an accompanying transfer of entropy. ...

In 1865, he came to define this ratio as entropy symbolized by S, such that, for a closed, stationary system: For a less technical and generally accessible introduction to the topic, see Introduction to entropy. ...

and thus, by reduction, quantities of heat δQ (an inexact differential) are defined as quantities of TdS (an exact differential): In physics, an inexact differential, as contrasted with an exact differential, of a function f is denoted: ; as is true of point functions. ... In mathematics, a differential dQ is said to be exact, as contrasted with an inexact differential, if the function Q exists. ...

In other words, the entropy function S facilitates the quantification and measurement of heat flow through a thermodynamic boundary. In thermodynamics, a boundary is a real or imaginary volumetric demarcation region drawn around a thermodynamic system across which quantities such as heat, mass, or work can flow. ...

[edit] Definitions

In modern terms, heat is concisely defined as energy in transit. Scottish physicist James Clerk Maxwell, in his 1871 classic Theory of Heat, was one of the first to enunciate a modern definition of “heat”. In short, Maxwell outlined four stipulations on the definition of heat. One, it is “something which may be transferred from one body to another”, as per the second law of thermodynamics. Two, it can be spoken of as a “measurable quantity”, and this treated mathematically like other measurable quantities. Third, it “can not be treated as a substance”; for it may be transformed into something which is not a substance, e.g. mechanical work. Lastly, it is “one of the forms of energy”. Similar such modern, succinct definitions of heat are as follows: James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères... The second law of thermodynamics is an expression of the universal law of increasing entropy. ... In physics, mechanical work is the amount of energy transferred by a force. ...

• In a thermodynamic sense, heat is never regarded as being stored within a body. Like work, it exists only as energy in transit from one body to another; in thermodynamic terminology, between a system and its surroundings. When energy in the form of heat is added to a system, it is stored not as heat but as kinetic and potential energy of the atoms and molecules making up the system.^[2]

• The noun heat is defined only during the process of energy transfer by conduction or radiation.^[5]

• Heat is defined as any spontaneous flow of energy from one object to another, caused by a difference in temperature between two objects.^[6]

• Heat may be defined as energy in transit from a high temperature object to a lower temperature object.^[7]

• Heat is an interaction between two closed systems without exchange of work is a pure heat interaction when the two systems, initially isolated and in a stable equilibrium, are placed in contact. The energy exchanged between the two systems is then called heat.^[8]

• Heat is a form of energy possessed by a substance by virtue of the vibrational movement, i.e. kinetic energy, of its molecules or atoms.^[9]

• Heat is the transfer of energy between substances of different temperatures.

• Heatis merely what happens when there is excess of mechanical energy

obtained due to some non conservative force acting on the body and this excess goes into the internal energy of the body which makes it hot eg. if we rub our hands together they get hot, why?Because they are getting excess of mechanical energy from our biochemical energy (from the food we eat) but it is being obtained due to the friction between our hands(a non conservative force)Hence this excess gets into the bulk of the skin material raising the internal energy hence they become hot. In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... hey BOYZZZZZ my name is VIVIAN MITCHELL and im from EDH CALIFORNIA i am so smart and HOTT thats why i have a BOYFRIEND sorry boyz im TAKEN! call me some time my numbaa is 916-337-9333 19-07 Can someone remove this retarded article please? ^^I think I... hey BOYZZZZZ my name is VIVIAN MITCHELL and im from EDH CALIFORNIA i am so smart and HOTT thats why i have a BOYFRIEND sorry boyz im TAKEN! call me some time my numbaa is 916-337-9333 19-07 Can someone remove this retarded article please? ^^I think I...

[edit] Thermodynamics

[edit] Internal energy

Heat is related to the internal energy U of the system and work W done by the system by the first law of thermodynamics: 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, work is the quantity of energy transferred from one system to another without an accompanying transfer of entropy. ... The first law of thermodynamics, a generalized expression of the law of the conservation of energy, states: // Description Essentially, the First Law of Thermodynamics declares that energy is conserved for a closed system, with heat and work being the forms of energy transfer. ...

which means that the energy of the system can change either via work or via heat flows across the boundary of the thermodynamic system. In more detail, Internal energy is 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 is comprised of the following types of energies:^[10] Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... 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...

The transfer of heat to an ideal gas at constant pressure increases the internal energy and performs boundary work (i.e. allows a control volume of gas to become larger or smaller), provided the volume is not constrained. Returning to the first law equation and separating the work term into two types, "boundary work" and "other" (e.g. shaft work performed by a compressor fan), yields the following: 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 evaporation. ... 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. ... Nuclear energy is energy released from the atomic nucleus. ... Nuclear energy is energy released from the atomic nucleus. ... 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 cold 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. ... In thermal physics, thermal energy is the energy portion of a system that increases with its temperature. ... The first law of thermodynamics, a generalized expression of the law of the conservation of energy, states: // Description Essentially, the First Law of Thermodynamics declares that energy is conserved for a closed system, with heat and work being the forms of energy transfer. ...

This combined quantity ΔU + W_boundary is enthalpy, H, one of the thermodynamic potentials. Both enthalpy, H, and internal energy, U are state functions. State functions return to their initial values upon completion of each cycle in cyclic processes such as that of a heat engine. In contrast, neither Q nor W are properties of a system and need not sum to zero over the steps of a cycle. The infinitesimal expression for heat, δQ, forms an inexact differential for processes involving work. However, for processes involving no change in volume, applied magnetic field, or other external parameters, δQ, forms an exact differential. Likewise, for adiabatic processes (no heat transfer), the expression for work forms an exact differential, but for processes involving transfer of heat it forms an inexact differential. 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. ... This article needs to be cleaned up to conform to a higher standard of quality. ... In thermodynamics, a state function, or state quantity, is a property of a system that depends only on the current state of the system, not on the way in which the system got to that state. ... A heat engine is a physical or theoretical device that converts thermal energy to mechanical output. ... In physics, an inexact differential, as contrasted with an exact differential, of a function f is denoted: ; as is true of point functions. ... In mathematics, a differential dQ is said to be exact, as contrasted with an inexact differential, if the function Q exists. ... In mathematics, a differential dQ is said to be exact, as contrasted with an inexact differential, if the function Q exists. ... In physics, an inexact differential, as contrasted with an exact differential, of a function f is denoted: ; as is true of point functions. ...

[edit] Heat capacity

For a simple compressible system such as an ideal gas inside a piston, the changes in enthalpy and internal energy can be related to the heat capacity at constant pressure and volume respectively. constrained to have constant volume, the heat, Q, required to change its temperature from an initial temperature, T₀, to a final temperature, T_f is given by: To meet Wikipedias quality standards, this article or section may require cleanup. ...

Removing the volume constraint and allowing the system to expand or contract at constant pressure:

For incompressible substances, such as solids and liquids, the distinction between the two types of heat capacity disappears as no work is performed. Heat capacity is an extensive quantity and as such is dependent on the number of molecules in the system. It can be represented as the product of mass, m , and specific heat capacity, according to: For other uses, see Solid (disambiguation). ... A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... In physics and chemistry, an extensive quantity (also referred to as an extensive variable) is a physical quantity whose value is proportional to the size of the system it describes. ... Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. ...

or is dependent on the number of moles and the molar heat capacity, according to: The mole (symbol: mol) is the SI base unit that measures an amount of substance. ...

The molar and specific heat capacities are dependent upon the internal degrees of freedom of the system and not on any external properties such as volume and number of molecules.

The specific heats of monatomic gases (e.g., helium) are nearly constant with temperature. Diatomic gases such as hydrogen display some temperature dependence, and triatomic gases (e.g., carbon dioxide) still more.

In liquids at sufficiently low temperatures, quantum effects become significant. An example is the behavior of bosons such as helium-4. For such substances, the behavior of heat capacity with temperature is discontinuous at the Bose-Einstein condensation point. Boson (game) Bosons, named after Satyendra Nath Bose, are particles which form totally-symmetric composite quantum states. ... A Bose–Einstein condensate is a phase of matter formed by bosons cooled to temperatures very near to absolute zero. ...

The quantum behavior of solids is adequately characterized by the Debye model. At temperatures well below the characteristic Debye temperature of a solid lattice, its specific heat will be proportional to the cube of absolute temperature. For low-temperature metals, a second term is needed to account for the behavior of the conduction electrons, an example of Fermi-Dirac statistics. The debye (symbol: D) is a non-SI and non-CGS unit of electrical dipole moment. ... In statistical mechanics, Fermi-Dirac statistics determines the statistical distribution of fermions over the energy states for a system in thermal equilibrium. ...

[edit] Changes of phase

The boiling point of water, at sea level and normal atmospheric pressure and temperature, will always be at nearly 100 °C no matter how much heat is added. The extra heat changes the phase of the water from liquid into water vapor. The heat added to change the phase of a substance in this way is said to be "hidden," and thus it is called latent heat (from the Latin latere meaning "to lie hidden"). Latent heat is the heat per unit mass necessary to change the state of a given substance, or: Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... It has been suggested that multiple sections of steam be merged into this article or section. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... For other uses, see Latin (disambiguation). ...

and

Note that as pressure increases, the L rises slightly. Here, M_o is the amount of mass initially in the new phase, and M is the amount of mass that ends up in the new phase. Also,L generally does not depend on the amount of mass that changes phase, so the equation can normally be written: This article or section is in need of attention from an expert on the subject. ...

Q = LΔm.

Sometimes L can be time-dependent if pressure and volume are changing with time, so that the integral can be written as:

[edit] Heat transfer mechanisms

Main article: Heat transfer

As mentioned previously, heat tends to move from a high temperature region to a low temperature region. This heat transfer may occur by the mechanisms of conduction and radiation. In engineering, the term convective heat transfer is used to describe the combined effects of conduction and fluid flow and is regarded as a third mechanism of heat transfer. In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. ... Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences. ... “Radiant heat” redirects here. ... Engineering is the applied science of acquiring and applying knowledge to design, analysis, and/or construction of works for practical purposes. ... Convection in the most general terms refers to the internal movement of currents within fluids (i. ...

[edit] Conduction

Conduction is the most significant means of heat transfer in a solid. On a microscopic scale, conduction occurs as hot, rapidly moving or vibrating atoms and molecules interact with neighboring atoms and molecules, transferring some of their energy (heat) to these neighboring atoms. In insulators the heat flux is carried almost entirely by phonon vibrations. Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... Thermal insulation on the Huygens probe The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. ... Normal modes of vibration progression through a crystal. ...

Fire test used to test the heat transfer through firestops and penetrants used in construction bounding.

The "electron fluid" of a conductive metallic solid conducts nearly all of the heat flux through the solid. Phonon flux is still present, but carries less than 1% of the energy. Electrons also conduct electric current through conductive solids, and the thermal and electrical conductivities of most metals have about the same ratio. A good electrical conductor, such as copper, usually also conducts heat well. The Peltier-Seebeck effect exhibits the propensity of electrons to conduct heat through an electrically conductive solid. Thermoelectricity is caused by the relationship between electrons, heat fluxes and electrical currents. Image File history File links Size of this preview: 736 × 599 pixelsFull resolution (2889 × 2352 pixel, file size: 478 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 736 × 599 pixelsFull resolution (2889 × 2352 pixel, file size: 478 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... A Fire Test is a means of determining whether or not fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation. ... Firestop after fire exposure during fire test in Tulsa, Oklahoma. ... A penetrant is the cause for a service penetration firestop. ... This article does not cite any references or sources. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In science and engineering, conductors, such as a electrical connector, are materials that readily conduct electric current through electrical conduction. ... Electric current is the flow (movement) of electric charge. ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... Electrical conductivity or specific conductivity is a measure of a materials ability to conduct an electric current. ... This article is about metallic materials. ... For other uses, see Copper (disambiguation). ... The Peltier-Seebeck effect, or thermoelectric effect, is the direct conversion of heat differentials to electric voltage and vice versa. ... Thermoelectricity is the conversion from temperature differentials to electricity or vice versa. ...

[edit] Convection

Convection is usually the dominant form of heat transfer in liquids and gases. This is a term used to characterize the combined effects of conduction and fluid flow. In convection, enthalpy transfer occurs by the movement of hot or cold portions of the fluid together with heat transfer by conduction. For example, when water is heated on a stove, hot water from the bottom of the pan rises, heating the water at the top of the pan. Two types of convection are commonly distinguished, free convection, in which gravity and buoyancy forces drive the fluid movement, and forced convection, where a fan, stirrer, or other means is used to move the fluid. Buoyant convection is because of the effects of gravity, and hence does not occur in microgravity environments. Convection in the most general terms refers to the internal movement of currents within fluids (i. ... 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. ... In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i. ... Astronauts on the International Space Station display an example of weightlessness Weightlessness is the experience (by people and objects) during freefall, of having no weight. ...

[edit] Radiation

Radiation is the only form of heat transfer that can occur in the absence of any form of medium; thus it is the only means of heat transfer through a vacuum. Thermal radiation is a direct result of the movements of atoms and molecules in a material. Since these atoms and molecules are composed of charged particles (protons and electrons), their movements result in the emission of electromagnetic radiation, which carries energy away from the surface. At the same time, the surface is constantly bombarded by radiation from the surroundings, resulting in the transfer of energy to the surface. Since the amount of emitted radiation increases with increasing temperature, a net transfer of energy from higher temperatures to lower temperatures results “Radiant heat” redirects here. ... Look up Vacuum in Wiktionary, the free dictionary. ... In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... For other uses, see Electron (disambiguation). ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ...

The power that a black body emits at various frequencies is described by Planck's law. There is a frequency f_max at which the power emitted is a maximum. Wien's displacement law, and the fact that the frequency of light is inversely proportional to its wavelength in vacuum, mean that the peak frequency f_maxis proportional to the absolute temperature T of the black body. The photosphere of the Sun, at a temperature of approximately 6000 K, emits radiation principally in the visible portion of the spectrum. The earth's atmosphere is partly transparent to visible light, and the light reaching the earth's surface is absorbed or reflected. The earth's surface emits the absorbed radiation, approximating the behavior of a black body at 300 K with spectral peak at f_max. At these lower frequencies, the atmosphere is largely opaque and radiation from earth's surface is absorbed or scattered by the atmosphere. Though some radiation escapes into space, it has been absorbed and subsequently re-emitted by atmospheric gases. It is this spectral selectivity of the atmosphere that is responsible for the planetary greenhouse effect As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... Black body spectrum For a general introduction, see black body. ... Wiens displacement law is a law of physics that states that there is an inverse relationship between the wavelength of the peak of the emission of a black body and its temperature. ... A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ...

The common household lightbulb has a spectrum overlapping the blackbody spectra of the sun and the earth. A portion of the photons emitted by a tungsten light bulb filament at 3000K are in the visible spectrum. However, most of the energy is associated with photons of longer wavelengths; these will not help a person see, but will still transfer heat to the environment, as can be deduced empirically by observing a household incandescent lightbulb. Whenever EM radiation is emitted and then absorbed, heat is transferred. This principle is used in microwave ovens, laser cutting, and RF hair removal. “Light bulb” redirects here. ... Color temperature is a characteristic of visible light that has important applications in photography, videography, publishing and other fields. ... It has been suggested that this article be split into articles entitled Microwave oven and Microwave heating. ... Laser cutting is a technology which uses a laser to cut materials, and is usually used in industrial manufacturing. ... Electrology is either of two electrical epilation methods for the permanent removal of human hair. ...

Heat exposure as part of a fire test for firestop products.

Image File history File links Size of this preview: 800 × 558 pixelsFull resolution (2970 × 2072 pixel, file size: 365 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 800 × 558 pixelsFull resolution (2970 × 2072 pixel, file size: 365 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... A Fire Test is a means of determining whether or not fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation. ... Firestop after fire exposure during fire test in Tulsa, Oklahoma. ...

[edit] Other heat transfer mechanisms

• Latent heat: Transfer of heat through a physical change in the medium such as water-to-ice or water-to-steam involves significant energy and is exploited in many ways: steam engine, refrigerator etc. (see latent heat of fusion)
• Heat pipes: Using latent heat and capillary action to move heat, heat pipes can carry many times as much heat as a similar sized copper rod. Originally invented for use in satellites, they are starting to have applications in personal computers.

In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... // The term steam engine may also refer to an entire railroad steam locomotive. ... “Freezer” redirects here. ... The latent heat of fusion of a substance is the amount of energy per unit mass required to turn a specified amount of the substance in its solid phase at its melting point to a liquid at the same temperature. ... A heat sink (aluminium) with heat pipe (copper) A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between the hot and cold interfaces. ... For other uses, please see Satellite (disambiguation) A satellite is an object that orbits another object (known as its primary). ...

[edit] Heat dissipation

In cold climates, houses with their heating systems form dissipative systems. In spite of efforts to insulate such houses to reduce heat losses to their exteriors, considerable heat is lost, or dissipated, from them, which can make their interiors uncomfortably cool or cold. For the comfort of its inhabitants, the interior of a house must be maintained out of thermal equilibrium with its external surroundings. In effect, domestic residences are oases of warmth in a sea of cold and the thermal gradient between the inside and outside is often quite steep. This can lead to problems such as condensation and uncomfortable draughts (drafts) which, if left unaddressed, can cause structural damage to the property. This is why modern insulation techniques are required to reduce heat loss. For other uses, see Condensation (disambiguation). ...

In such a house, a thermostat is a device capable of starting the heating system when the house's interior falls below a set temperature, and of stopping that same system when another (higher) set temperature has been achieved. Thus the thermostat controls the flow of energy into the house, that energy eventually being dissipated to the exterior. Bi-metallic thermostat for buildings A thermostat is a device for regulating the temperature of a system so that the systems temperature is maintained near a desired setpoint temperature. ...

[edit] References

[edit] See also

Defrosting is a procedure, performed periodically on refrigerators and freezers to maintain their operating effiency. ... Figure 1 This is a diagram of the seasons. ... The heat death is a possible final state of the universe, in which it has run down to a state of no free energy to sustain motion or life. ... The heat equation is an important partial differential equation which describes the variation of temperature in a given region over time. ... In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. ... A heat exchanger is a device built for efficient heat transfer from one fluid to another, whether the fluids are separated by a solid wall so that they never mix, or the fluids are directly contacted. ... The heat transfer coefficient is used as a fudge factor in calculating heat transfer in thermodynamics. ... 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 the vector animation platform, see Macromedia Shockwave. ... For other uses, see Temperature (disambiguation). ... It has been suggested that List of temperature sensors be merged into this article or section. ...

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