Difference between revisions of "Entropy"

From Glossary of Meteorology
imported>Perlwikibot
 
Line 9: Line 9:
 
   </div>
 
   </div>
  
<div class="definition"><div class="short_definition">A thermodynamic [[state variable]] denoted by ''S'' (''s'' denotes [[specific entropy]], entropy per  unit mass).</div><br/> <div class="paragraph">The rate of change of entropy of a thermodynamic system is defined as  <div class="display-formula"><blockquote>[[File:ams2001glos-Ee30.gif|link=|center|ams2001glos-Ee30]]</blockquote></div> where ''Q'' is the heating rate in a [[reversible process]] and ''T'' is [[absolute]] temperature. Integration  of this equation yields the entropy difference between two states. The entropy of an [[isolated system|isolated  system]] cannot decrease in any real physical process, which is one statement of the [[second law of thermodynamics|second law  of thermodynamics]]. The [[specific entropy]] of an [[ideal gas]], ''s''<sub>''g''</sub>, may be expressed as  <div class="display-formula"><blockquote>[[File:ams2001glos-Ee31.gif|link=|center|ams2001glos-Ee31]]</blockquote></div> where ''c''<sub>''pg''</sub> is the [[specific heat]] at constant pressure of that gas, ''R''<sub>''g''</sub> is its [[gas constant]], and ''T'' and  ''p''<sub>''g''</sub> are its [[temperature]] and [[pressure]]. The entropy of a liquid, ''s''<sub>''l''</sub>;t7, is  <div class="display-formula"><blockquote>[[File:ams2001glos-Ee32.gif|link=|center|ams2001glos-Ee32]]</blockquote></div> where ''c''<sub>''l''</sub> is the specific heat of the liquid.</div><br/> </div>
+
<div class="definition"><div class="short_definition">A thermodynamic [[state variable]] denoted by ''S'' (''s'' denotes [[specific entropy]], entropy per  unit mass).</div><br/> <div class="paragraph">The rate of change of entropy of a thermodynamic system is defined as  <div class="display-formula"><blockquote>[[File:ams2001glos-Ee30.gif|link=|center|ams2001glos-Ee30]]</blockquote></div> where ''Q'' is the heating rate in a [[reversible process]] and ''T'' is [[absolute]] temperature. Integration  of this equation yields the entropy difference between two states. The entropy of an [[isolated system|isolated  system]] cannot decrease in any real physical process, which is one statement of the [[second law of thermodynamics|second law  of thermodynamics]]. The [[specific entropy]] of an [[ideal gas]], ''s''<sub>''g''</sub>, may be expressed as  <div class="display-formula"><blockquote>[[File:ams2001glos-Ee31.gif|link=|center|ams2001glos-Ee31]]</blockquote></div> where ''c''<sub>''pg''</sub> is the [[specific heat]] at constant pressure of that gas, ''R''<sub>''g''</sub> is its [[gas constant]], and ''T'' and  ''p''<sub>''g''</sub> are its [[temperature]] and [[pressure]]. The entropy of a liquid ''s''<sub>''l''</sub> is  <div class="display-formula"><blockquote>[[File:ams2001glos-Ee32.gif|link=|center|ams2001glos-Ee32]]</blockquote></div> where ''c''<sub>''l''</sub> is the specific heat of the liquid.</div><br/> </div>
 
</div>
 
</div>
  

Latest revision as of 12:15, 17 June 2021



entropy

A thermodynamic state variable denoted by S (s denotes specific entropy, entropy per unit mass).

The rate of change of entropy of a thermodynamic system is defined as
ams2001glos-Ee30
where Q is the heating rate in a reversible process and T is absolute temperature. Integration of this equation yields the entropy difference between two states. The entropy of an isolated system cannot decrease in any real physical process, which is one statement of the second law of thermodynamics. The specific entropy of an ideal gas, sg, may be expressed as
ams2001glos-Ee31
where cpg is the specific heat at constant pressure of that gas, Rg is its gas constant, and T and pg are its temperature and pressure. The entropy of a liquid sl is
ams2001glos-Ee32
where cl is the specific heat of the liquid.


Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact permissions@ametsoc.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.