作者Lance0616 (风翼)
看板Grad-ProbAsk
标题[理工] [普物]-热物理 - entropy
时间Sun Dec 13 15:28:33 2009
题目：
A mole of an ideal gas undergoes a reversible isothermal expansion from
V to 2V. The change ites entropy of the universe is _(a)_ ? Suppose the
same expansion takes place as an adibatic free expansion, the change in
entropy of the universe is _(b)_ ?
问题
1. unverse的定义是什麽? 是total entropy = system + environment = universe 吗?
2. 所以对於(a)，答案是0还是-nRln2
0的想法：因为是reversible，所以total entropy变化不会变(假设universe=total)
-nRln2是假设Unverse=enviroment
3. (b)是>0还是0
>0是因为膨胀，然後Vf>Vi entropy change=nRln(Vf/Vi)>0
Su=Se+Ss=0+nRln(Vf/Vi) 为什麽环境的entropy change会是0
类题：
In a reversible adiabatic process the entropy of an ideal gas dows not change.
证明他是0
但是根据我问的(b)他没有提到reversible所以到底是?
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※ 编辑: Lance0616 来自: 114.45.99.161 (12/13 16:05)
1F：推 IMISSA:问题一指的应该是Stotal吧 12/13 16:15