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In thermodynamics, work is the quantity of energy transferred from one system to another without an accompanying transfer of entropy. It is a generalization of the concept of mechanical work in mechanics. In the SI system of measurement, work is measured in joules (symbol: J). The rate at which work is performed is power. This article needs to be cleaned up to conform to a higher standard of quality. ...
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 Helmholtz free energy is a thermodynamic potential which measures the “useful†work obtainable from a closed thermodynamic system at a constant temperature. ...
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 thermodynamics, the Gibbs free energy is a thermodynamic potential which measures the useful work obtainable from a closed thermodynamic system at a constant temperature and pressure. ...
Thermodynamics (from the Greek θεÏμη, 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. ...
For a less technical and generally accessible introduction to the topic, see Introduction to entropy. ...
In physics, mechanical work is the amount of energy transferred by a force. ...
“SI†redirects here. ...
The joule (IPA: or ) (symbol: J) is the SI unit of energy. ...
In physics, power (symbol: P) is the rate at which work is performed or energy is transferred. ...
History
1824 Work, i.e. "weight lifted through a height", was originally defined in 1824 by Sadi Carnot in his famous paper Reflections on the Motive Power of Fire. Specifically, according to Carnot: Sadi Carnot in the dress uniform of a student of the École polytechnique Nicolas Léonard Sadi Carnot (June 1, 1796 - August 24, 1832) was a French physicist and military engineer who gave the first successful theoretical account of heat engines, now known as the Carnot cycle, thereby laying the...
| “ | We use here motive power (work) to express the useful effect that a motor is capable of producing. This effect can always be likened to the elevation of a weight to a certain height. It has, as we know, as a measure, the product of the weight multiplied by the height to which it is raised. | ” | In thermodynamics, motive power is an agency, as water or steam, used to impart motion. ...
A motor is a device that converts energy into mechanical power, and is often synonymous with engine. ...
1845 In 1845, the English physicist James Joule wrote a paper On the mechanical equivalent of heat for the British Association meeting in Cambridge[1]. In this work, he reported his best-known experiment, in which the work released through the action of a "weight falling through a height" was used to turn a paddle-wheel in an insulated barrel of water. Image File history File links Download high-resolution version (1684x1387, 1231 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Conservation of energy James Prescott Joule Work (thermodynamics) ...
Image File history File links Download high-resolution version (1684x1387, 1231 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Conservation of energy James Prescott Joule Work (thermodynamics) ...
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. ...
James Prescott Joule (December 24, 1818–October 11, 1889) was an English physicist, born in Salford, near Manchester. ...
This article is about the city in England. ...
In physics, mechanical work is the amount of energy transferred by a force. ...
In this experiment, the friction and agitation of the paddle-wheel on the body of water caused heat to be generated which, in turn, increased the temperature of water. Both the temperature change ∆T of the water and the height of the fall ∆h of the weight mg were recorded. Using these values, Joule was able to determine the mechanical equivalent of heat. Joule estimated a mechanical equivalent of heat to be 819 ft•lbf/Btu (4.41 J/cal). The modern day definitions of heat, work, temperature, and energy all have connection to this experiment. 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. ...
For other uses, see Temperature (disambiguation). ...
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. ...
Overview According to the First Law of Thermodynamics, it is useful to separate changes to the internal energy of a thermodynamic system into two sorts of energy transfers. Work refers to forms of energy transfer which can be accounted for in terms of changes in the macroscopic physical variables of the system, for example energy which goes into expanding the volume of a system against an external pressure, by driving a piston-head out of a cylinder against an external force. This is in contrast to heat energy, which is carried into or out of the system in the form of transfers in the microscopic thermal motions of particles. 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. ...
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 concept of thermodynamic work is slightly more general than that of mechanical work because it includes other types of energy transfers as well. The electrical work required to move a charge against an external electrical field can be measured, as can the work required to move heat against a temperature gradient. An extremely important fact to understand is that thermodynamic work need not have any mechanical component to be considered such.
Mathematical definition According to the First Law of Thermodynamics, any net increase in the internal energy U of a thermodynamic system must be fully accounted for, in terms of heat δQ entering the system minus work δW done by the system:  The letter d indicates that internal energy U is a property of the state of the system, so changes in the internal energy are exact differentials; they depend only on the original state and the final state, and not upon the path taken. In contrast, the Greek δs in this equation reflect the fact that the heat transfer and the work transfer are not properties of the final state of the system. Given only the initial state and the final state of the system, one can only say what the total change in internal energy was, not how much of the energy went out as heat, and how much as work. This can be summarized by saying that heat and work are not state functions of the system. In mathematics, a differential dQ is said to be exact, as contrasted with an inexact differential, if the function Q exists. ...
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. ...
Pressure-volume work Chemical thermodynamics studies PV work, which occurs when the volume of a fluid changes. PV work is represented by the following differential equation: Willard Gibbs - founder of chemical thermodynamics In thermodynamics, chemical thermodynamics is the mathematical study of the interrelation of heat and work with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics. ...
A simulation of airflow into a duct using the Navier-Stokes equations A differential equation is a mathematical equation for an unknown function of one or several variables which relates the values of the function itself and of its derivatives of various orders. ...
 where: - W = work done on the system
- P = external pressure
- V = volume
Therefore, we have:  Like all work functions, PV work is path-dependent. (The path in question is a curve in the Euclidean space specified by the fluid's pressure and volume, and infinitely many such curves are possible.) From a thermodynamic perspective, this fact implies that PV work is not a state function. This means that the differential dW is an inexact differential; to be more rigorous, it should be written đW (with a line through the d). Path-dependence exists when the outcome of a process depends on its past history, on the entire sequence of decisions made by agents and resulting outcomes, and not just on contemporary conditions. ...
Around 300 BC, the Greek mathematician Euclid laid down the rules of what has now come to be called Euclidean geometry, which is the study of the relationships between angles and distances in space. ...
This article is about pressure in the physical sciences. ...
For other uses, see Volume (disambiguation). ...
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. ...
In physics, an inexact differential, as contrasted with an exact differential, of a function f is denoted: ; as is true of point functions. ...
In other words, from a mathematical point of view, đW is not an exact one-form. The line-through is merely a flag to warn us there is actually no function (0-form) W which is the potential of đW>. If there were, indeed, this function W, we should be able to just use Stokes Theorem to evaluate this putative function, the potential of đW, at the boundary of the path, that is, the initial and final points, and therefore the work would be a state function. This impossibility is consistent with the fact that it does not make sense to refer to the work on a point in the PV diagram; work presupposes a path. In mathematics, both in vector calculus and in differential topology, the concepts of closed form and exact form are defined for differential forms, by the equations dα = 0 for a given form α to be a closed form, and α = dβ for an exact form, with α given...
In linear algebra a one-form on a vector space is the same as a linear functional on it. ...
A differential form is a mathematical concept in the fields of multivariate calculus, differential topology and tensors. ...
In physics, a potential may refer to the scalar potential or to the vector potential. ...
Stokes Theorem in differential geometry is a statement about the integration of differential forms which generalizes several theorems from vector calculus. ...
Look up Boundary in Wiktionary, the free dictionary. ...
PV work is often measured in the (non-SI) units of litre-atmospheres, where 1 L·atm = 101.3 J.
Free energy and exergy The amount of useful work which can be extracted from a thermodynamic system is discussed in the article Second Law of Thermodynamics. Under many practical situations this can be represented by the thermodynamic Availability or Exergy function. Two important cases are: in thermodynamic systems where the temperature and volume are held constant, the measure of "useful" work attainable is the Helmholtz free energy function; and in systems where the temperature and pressure are held constant, the measure of "useful" work attainable is to the Gibbs free energy. The second law of thermodynamics is an expression of the universal law of increasing entropy. ...
Exergy is defined differently in different fields of study. ...
Exergy is defined differently in different fields of study. ...
In thermodynamics, the Helmholtz free energy is a thermodynamic potential which measures the “useful†work obtainable from a closed thermodynamic system at a constant temperature. ...
In thermodynamics, the Gibbs free energy is a thermodynamic potential which measures the useful work obtainable from a closed thermodynamic system at a constant temperature and pressure. ...
See also Thermodynamics (from the Greek θεÏμη, 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. ...
For other uses, see Chemistry (disambiguation). ...
Chemical reactions are also known as chemical changes. ...
References - ^ Joule, J.P. (1845) "On the Mechanical Equivalent of Heat", Brit. Assoc. Rep., trans. Chemical Sect, p.31, which was read before the British Association at Cambridge, June
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