那么我们有了这条可逆绝热路径。
现在约束改成了,绝热膨胀，或者压缩。
Our constraint is going to be an adiabatic expansion or compression.
一个是等温，一个是绝热。
各种定义，学生：绝热过程是可逆的吗？
We're pretty much done with our definitions STUDENT: Was adiabatic reversible?
通过绝热膨胀到，第3点。
我们再来研究绝热过程。
这是一个绝热过程。
因此，要选择吸水率小的绝热材料。
Therefore, to choose bibulous rate small insulation materials.
我们知道在绝热膨胀过程中，系统温度会降低。
We know in an adiabatic expansion the system's going to cool.
杯子并不十分绝热。
绝热压缩，的情况，与此相反。
In the opposite case, if you have a compression, then it's the opposite of expansion.
现在我们进行另外一步，绝热收缩过程。
And now we're going to have another adiabatic step, an adiabatic compression.
所以它是绝热的。
绝热可逆路径。
记得绝热意味着什么吗？
这种反应叫做非绝热反应。
对，没错，它是绝热的。
水泥周围的良绝热体又有利于温度的增高。
A good insulation around the cement favours an temperature increase.
这仍然是绝热的，是隔热的，但现在它的体积是恒定的。
So this is still adiabatic. It's insulated, but now it's constant volume, OK.
然后有另外一个绝热过程，绝热压缩到4点。
Then we're going to have another isothermal step, a compression to some point four.
橡胶是超好的绝热材料，可以节省取暖费用。
好，现在系统有恒定的温度，因为它是绝热的。
OK, so we have constant temperature, because it's isothermal.
我们慢慢改变外部压强，这个过程也是绝热的。
We've changed the external pressure slowly, and again this is isothermal.
你的时间足够快以至于，基本上是一个绝热过程。
So your time scale it just fast enough that this is basically an adiabatic compassion.
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？
So when I expand this gas adiabatically and it cools down, why do you think it might cool down?
它是利用材料表面的辐射特性来获得绝热保温效能。
It is the use of radiation characteristics on the surface of the material for insulation performance.
现在是可逆绝热过程，因此这里有一个关系式，我相信你们还记得。
Now, this is a reversible adiabatic path, so there's a relationship that I'm sure you'll remember.
这个绝热过程的温度是,比T1低，因为这是个膨胀过程。
T2 So this is an isotherm at some different temperature T2, a cooler temperature, because this was an expansion.
这个绝热过程的温度是,比T1低，因为这是个膨胀过程。
T2 So this is an isotherm at some different temperature T2, a cooler temperature, because this was an expansion.
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