It's related to the heat capacity, the constant volume of heat capacity and something you could measure.
它联系了热能,恒容热容和一些,我们能够测量的物理量。
When I flail my arms around I generate work and heat. This is not a constant volume process.
这不是一个恒容过程,但如果我是一个系统,当我做这些的时候。
You just change volume to pressure and basically you're looking at enthalpy under a constant -- anything that's done at a constant volume path with energy, there's the same thing happening under constant pressure path for enthalpy.
可以看到这就是把体积换成了压强,一般我们都是在一种恒定状态下,考虑焓的,任何在恒容条件下,能伴随能量变化的东西,也在恒压条件下伴随焓同样地变化,所以你可以经常。
It's not constant pressure, because we have a delta p going on. It's not constant volume either.
也不是恒容,这个限制,是这个实验的限制。
v du/dV under constant temperature. du/dT v under constant volume. You use the Joule expansion to find these quantities.
像偏u偏v,恒温下的偏u偏,恒容下的偏u偏,你们知道怎么运用焦耳定律。
Over here, we have dq=Cp dT, the heat, the proportionality between heat - and temperature rise is given by this, the constant pressure heat capacity.
这里我有dq=CpdT,这是热量,这是联系热量,和温度变化的系数,恒压热容。
If you have a real gas and you write du is Cv dT and your path is not a constant volume path, then you are making a mistake. But for an ideal gas, you can always write this. And this turns out to be very useful to remember.
对于真实气体,如果其变化过程,不是恒容的,du=Cv*dT就不成立,但对于理想气体,这条规则永远成立,这一点非常有用,请记住。
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