Difference between revisions of "Thermodynamics"

Revision as of 21:31, June 4, 2010

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-'''Thermodynamics''' is the study of the effects of work, heat, and energy on a system. Thermodynamics is only concerned with so-called ''macroscopic'' observations, which are observations on large numbers of particles.<ref>http://www.grc.nasa.gov/WWW/K-12/airplane/thermo.html</ref>
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-==Thermodynamics and statistical mechanics==
-For systems consisting of many particles (such as a [[gas]] consisting of many [[molecule]]s), it is possible to describe and predict the properties of the system accurately, even though it is virtually impossible to know what individual particles do. In essence, because of the large number of particles, one can apply [[statistics]] to learn about the "average" behavior of the system. The branch of [[physics]] known as [[statistical mechanics]] does just this.
-"Classical" thermodynamics, on the other hand, predates this field, and makes ''no'' explicit reference to the constituent particles of a system. It consists of a number of "empirical" laws, which are derived purely from observations on thermodynamical systems, such as vessels of gas, or [[steam engine]]s. Well-known "laws" of thermodynamics are:<ref>Mark W. Zemansky, ''Heat and Thermodynamics'', McGraw-Hill, New York, 1957</ref>
-;[[The Zeroth Law of Thermodynamics]]
-:allows us to define the concept of [[temperature]], by stating that "''Two systems in thermal [[equilibrium]] with a third one are in thermal equilibrium with each other''". This law is called "zeroth" because it was only formulated after the three others, but is actually more fundamental, and hence deserves a lower number.
-;[[The First Law of Thermodynamics]]
-:states that [[energy]] is conserved and that [[heat]] and [[work]] are transfers of energy.
-; [[Second Law of Thermodynamics|The Second Law of Thermodynamics]]
-:states (in one of its various formulations) that [[entropy]] in an isolated system cannot decrease, and that ''irreversible processes'' can only make it increase.<ref>Gregory H. Wannier, ''Statistical Physics'', John Wiley & Sons, New York, 1966</ref> An equivalent formulation states that heat cannot spontaneously flow from a cooler body to a hotter body.
-;[[The Third Law of Thermodynamics]]
-:also known as ''Nernst's Law'', states that it is not possible to bring any system to the [[absolute zero]] of temperature in a finite number of operations. Also stated as follows: The entropy of a perfect crystal at absolute zero is zero.
-These laws tell us to what constraints ''any'' system is subject. For example, it allows us to calculate the maximum possible efficiency of an [[engine]] once we know the temperature at which it operates.
-The particular properties of a specific system cannot be calculated from these laws alone. More information is required: so-called ''thermodynamic equations of state'' tell us how a particular system will behave under thermodynamic processes. A simple example of such an equation is the [[Ideal Gas Law]] that applies to dilute gases.
-== References ==
-<div class="references-small">
-<references />
-</div>
-[[category:physics]]

Difference between revisions of "Thermodynamics"

Revision as of 21:31, June 4, 2010

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