dT/dp is mu JT. So for a real gas like air, this is a positive number. It's not zero.

所以对于像空气这样的真实气体，这是一个正数，不等于零。

麻省理工公开课 - 热力学与动力学课程节选

Let's try it with a different equation of state, that isn't quite as simple as the ideal gas case.

考虑一个不同的状态方程，这状态方程不像理想气体状态方程那么简单。

麻省理工公开课 - 热力学与动力学课程节选

So, one difference between photoelectron spectroscopy and, for example, the photoelectric effect is that in this case, we're not just looking at one energy level, which is what we were looking at from the surface of a metal, now we're talking about this gaseous atom.

光电子能谱与光电效应的不同点在于，以这种情况为例，我们不只关心一个能级，就像原来在金属表面那样，现在我们研究的是气体原子，所以，我们可以从原子中。

麻省理工公开课 - 化学原理课程节选

This needs to be stressed that this is the ideal gas case. Now regular gases, real gases fortunately as I said, don't obey this.

需要强调的是这是对理想气体而言的,普通气体，真实气体，就像我说过的,不遵循这个规律，这是非常重要的。

麻省理工公开课 - 热力学与动力学课程节选

Real refrigerators actually work with liquids that go into gases so use the latent heat of the liquid, so it doesn't really work like the Joule-Thomson expansion. So this is real.

液体变成气体来工作,以运用液体的潜热，所以这不是,真正像焦耳-汤姆逊膨胀一样工作,这是真实的气体，不像焦耳。

麻省理工公开课 - 热力学与动力学课程节选

And so now, instead of using these reference points for the Kelvin scale, we use the absolute zero, which isn't going to care what the pressure is.

就像理想气体温标,与气体的种类无关一样，具有普适性，在开尔文温标中。

麻省理工公开课 - 热力学与动力学课程节选

It's like the ideal gas law, and one could know that in principle.

有点像理想气体定律，我们可以从原理上理解这点。

麻省理工公开课 - 热力学与动力学课程节选

but right now you're going to have to take it for granted. So, if the Joule-Thomson coefficient is equal to zero, just like we wrote, du = Cv dT du = Cv dT for an ideal gas, we're going to dH = Cp dT have dH = Cp dT for an ideal gas as well.

但是现在请你们应该把它看成理所当然的,所以，如果焦耳-汤姆逊系数等于零,就像我们写的，对于理想气体,我们也可以得到对于理想气体。

麻省理工公开课 - 热力学与动力学课程节选