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Now for this experiment, this is a constant enthalpy experiment for the Joule-Thomson experiment, this is equal to zero.
对于这个实验，焦耳-汤姆逊实验,是一个焓不变的实验,焓变化等于0，所以我可以。
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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。
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So, this is actually kind of neat to point out, because we all remember J.J. Thomson Thomson J J Thomson from our second lecture, and J.J. Thomson got a Nobel Prize in 1906 for showing that electrons exist in that they are particles.
所以，这个确实需要要指出，因为我们都记得第二堂课,讲到的,因为发现了电子具有粒子性,在1906年获得了诺贝尔奖。
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I want to cool a gas with a Joule-Thomson experiment, what temperature do I have to be at?
给气体降温时,需要到达什么温度？
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What we've been talking about, the Joule-Thomson experiment, constant enthalpy process?
首先，刚才说的，那些有什么问题吗？,焦耳-汤姆逊实验，等焓过程？
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And if that's equal to zero, that means that the Joule-Thomson coefficient for an ideal gas is also equal to zero. We're going to actually prove this later in the course.
说明理想气体的,焦耳-汤姆逊系数也等于0。,详细的证明过程,会在以后的课上给出。
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OK, so we ended up last time, we talked about Joule-Thomson expansion, which is an irreversible expansion through a nozzle, through a porous plug, constant enthalpy expansion.
上节课，我们讨论了焦耳-汤姆逊，膨胀过程,也就是气体，通过毛细管。
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OK, the Joule-Thomson experiment.
焦耳-汤姆逊实验。
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And that's what Thomson did.
其他人之前也提出过这种说法。
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This is equal to zero. So this irreversible process this Joule-Thomson process, is a constant enthalpy process. Delta h for this process is equal to zero.
等于0。所以这个不可逆过程,也就是焦耳-汤姆逊过程,是一个等焓过程。
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We use a liquid helium. And so in order to make a liquid helium, you can't take helium at room temperature and do this, because if you did, you would just heat it up, because the room temperature is above the inversion temperature, so Joule-Thomson would heat up the helium.
为了得到液氦,不能再常温,做这个实验,否则就是加热氦气，因为室温高于它的转变温度,所以焦耳-汤姆孙，实验会加热氦气。
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The Joule experiment was a constant energy experiment, right. Here we're going to have to find a constant enthalpy experiment, and that is going to be the Joule-Thomson experiment. That's going to extract out a physical meaning to this derivative here.
非常像焦耳实验,焦耳实验是一个能量恒定的实验,我们这里要做的是，找到一个焓不变的实验,也就是焦耳-汤姆逊实验,这个实验可以把这里的微分式形象化。
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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。
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And so they defined them, p after many experiments, the limit of this 0 delta T delta p and the limit of delta p goes to zero as the Joule-Thomson coefficient.
他们定义了这些量，以及它们的范围，ΔT比Δ,Δp的极限趋近于,叫做焦耳-汤姆逊系数。
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And what we did was he put two detection plates on either side of these cathode rays, and when he put a voltage difference between these two plates, he wanted to see if he could actually bend the rays and test if they're actually charged or not.
但没有实验证明这件事,这就是Thomson所做的，它在阴极射线旁边放两块探测板,他想通过看当他,在两板之间加上电压后,阴极射线是不是会。
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The Joule-Thomson experiment is irreversible.
实验是一个不可逆过程。
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The Joule-Thomson coefficient is equal to zero.
焦耳-汤姆逊系数等于。
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So you need first to take the liquid helium and cool it below 53 degrees Kelvin before you can do the Joule-Thomson to cool it even further to make liquid helium.
我们首先需要,把温度江都53k一下,然后利用焦耳-汤姆孙实验,来继续冷却它。
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So, Thomson came up with a model for the atom due to this, and this is called the Plum Pudding model of the atom, and he was, as we said, English, so plum pudding is kind of a British food.
所以Thompson因此,想到了一个原子模型,他把它叫做，李子布丁模型，我们说过他是英国人。
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So in this experiment here, delta p is less than zero. You need to have this whole thing greater than zero. So delta T is less than zero as well. So if you're below the inversion temperature and you do the Joule-Thomson experiment, you're going to end up with something that's colder on this side than that side.
所以在这个实验中，Δp小于零,这全部都大于零,因此ΔT也小于零,所以如果在低于转变,温度的情况下做焦耳-汤姆孙实验,最后的结果是,这边的温度比这边低。
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