So when I expand this gas adiabatically and it cools down, why do you think it might cool down?
现在我们知道了气体绝热膨胀时,温度会下载,为什么会降温?
For a real gas it depends on more than the temperature STUDENT: Are there any other constraints similar to that .
而对实际气体,这是不对的,它的内能不仅仅依赖于温度,学生:有其他,类似的约束吗?
Avogadro was a professor of chemistry at the University of Turin who did a lot of work on gas laws, understanding the number of gas particles in a given volume at a given temperature.
阿伏加德罗是一个化学教授,在都灵大学,他做了很多关于气体定律的研究,了解气体微粒,在特定的容量和温度下的数目。
It's going to have some volume, temperature to begin with, and then we're going to do something to it.
气体有一定的,体积与温度,现在我们。
The last time you saw that for an ideal gas, the energy only cared about the temperature.
上次你们知道了,理想气体的能量只与温度有关。
Now, we saw before, or really I should say we accepted before, that for an ideal gas, u was a function of temperature only.
我们已经看到,或者说我们已经接受这样一个事实,即理想气体的内能只和温度有关。
The only function it is -- it doesn't care where the gas is. It only cares where the temperature is.
是温度的函数,它只是温度的函数,不管是什么气体。
But if you touch the valve going into your tire which basically measures the temperature of the air going into your tire, that is getting hot, right.
以至于浑身发热,如果你摸气筒的阀门,相当于近似测量了进入轮胎的气体的温度,它会很热,对吧。
So that you could see that for the ideal gas, u would not be a function of volume, but only of temperature.
所以我们可以看到对理想气体,内能不依赖于体积,而仅仅是温度的函数。
So for an ideal gas, we saw that u was only a function of temperature.
对于理想气体,我们知道内能只是温度的函数。
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?
OK, for most gases, T inversion is much 300K greater than 300 degrees Kelvin. Much greater than room temperature.
好,对大多数气体,转变温度都高于,比室温高很多。
And that will end up winning out at basically any realistic temperature where the stuff really is a gas.
在体系仍然处于气体状态的温度下,熵战胜了能量。
Your plant is going to blow up, because the ideal gas law works only in very small range of pressures and temperatures for most gases.
理想气体定律,只在一个很小的压强,与温度的范围内适用。
B=0 There's going to be some temperature where B is equal to zero. In that case, your gas is going to look awfully like an ideal gas.
在某个温度,这时,实际气体的表现,十分接近理想气体,高于这一温度它是正的。
Great. So now we have this ideal gas thermometer, and out of this ideal gas thermometer, also comes out the ideal gas law.
好,现在我们有了理想气体温度计,由此还可以引出理想气体定律,我们可以得到这条,插值出的直线的斜率。
All right, next time we're going to talk about a much better scale, which is the ideal gas thermometer and how we get to the Kelvin scale.
好,下次我们,会讲一种好得多的温标,关于理想气体温度计,和开氏温标的导出。
And so an experiment said the gas didn't increase its temperature when it expanded the vacuum.
这个实验告诉你,气体在向真空膨胀的过程,中温度没有升高。
And you can find these compressibility factors in tables. If you want to know the compressibility factors for water, for steam, at a certain pressure and temperature, you go to a table and you find it.
各种气体的压缩系数,想知道水或者水蒸气,在某个温度和压强下的,压缩系数,查表就行了,这是实际气体状态方程的。
When you expand a real gas into vacuum, the temperature goes down.
当一个真实气体,向真空膨胀咱的时候温度会下降。
And on the other side of that temperature you end up heating if you compress.
而在另一边的温度上,压缩气体将导致升温。
We call that inversion because on one side you end up cooling if you compress.
因为在这个温度的一边,当你压缩气体时气体降温。
We just treated the one case of an ideal gas as the temperature is reduced.
我们只是讨论了温度下降时,理想气体的行为。
It only cares what temperature is. If temperature is constant, there's no change in energy.
如果温度是常数,能量就没有变化,对理想气体。
let's use the ideal gas law to get rid of the temperature.
我们用理想气体定律,来消去温度。
Ideal gas would be the same temperature.
而理想气体的话两边温度将一样。
Pressure has dropped out of the picture completely here. So there is no p dependence here.
理想气体的H只是温度的函数,这对于真实气体来说是。
That's going to be your heating up of the gas.
这样气体的温度将会升高。
But now, so this is where the refrigeration comes in. So if you take a gas, and you're below the inversion temperature and you make it go through this irreversible process, the gas comes out colder from that side than that side.
这就是冰箱的原理,如果在低于转变温度,的情况下我们将气体经过,这个不可逆过程,气体出来的温度将比这边低。
What happened to the temperature in a Joule expansion in ideal gas?
对理想气体,焦耳-汤姆逊膨胀过程中温度如何变化?
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