Difference between revisions of "Entropy"
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Entropy
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1. A measure of the extent to which the energy of a system is unavailable.
A mathematically defined thermodynamic function of state, the increase in
which gives a measure of the energy of a system which has ceased to be
available for work during a certain process:
specific entropy; u is specific internal energy; p is pressure; v is specific volume; T is Kelvin temperature; and q is heat per unit mass. For reversible processes,
specific heat at constant pressure. See third
law of thermodynamics.
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In an adiabatic process, the entropy increases if the process is
irreversible and remains unchanged if the process is reversible. Thus, since
all natural processes are irreversible, it is said that in an isolated system
the entropy is always increasing as the system tends toward equilibrium, a
statement which may be considered a form of the second law of thermodynamics.
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2. In communication theory, average
information content.
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References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
