View source for Second law of thermodynamics



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== second law of thermodynamics ==
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<div class="definition"><div class="short_definition">An inequality that is fundamentally different from the [[first law of thermodynamics|first law]]  because it specifies the direction in which a natural process will evolve rather than merely requiring  that certain quantities are conserved.</div><br/> <div class="paragraph">As formulated by Planck, the second law asserts that a thermodynamic state function, ''S'', known  as [[entropy]], exists for all physical systems. For the universe and for a system isolated from its  surroundings,  <div class="display-formula"><blockquote>[[File:ams2001glos-Se11.gif|link=|center|ams2001glos-Se11]]</blockquote></div> Equality prevails only for reversible processes or when the system is in a [[steady state]]. When the  universe of a system is a maximum, no further evolution of the system is possible. The second law  is often asserted in other forms, including the following.  
:<div class="list_item">When two bodies at different temperatures interact, the [[temperature]] of the hotter body can  only decrease and that of the colder body can only increase unless [[work]] is done.</div> 
:<div class="list_item">No device can continuously deliver mechanical work and produce no effect other than cooling  a [[reservoir]].</div> 
:<div class="list_item">In the neighborhood of every state that can be reached reversibly, there exist states that cannot  be reached by a reversible, [[adiabatic process]], or, in other words, that can be reached only  irreversibly or cannot be reached at all.</div><br/></div><br/></div><div class="reference">Dutton, J. A. 1995. Dynamics of Atmospheric Motion. Dover Press, . 45&ndash;51, 406&ndash;410. </div><br/> <div class="reference">Sommerfeld, A. 1964. Thermodynamics and Statistical Mechanics. Academic Press, . 26&ndash;36, 39. </div><br/> 
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