PROFESSOR BAWENDI: The only But it's hard to imagine an irreversible compression the way we can just imagine an irreversible expansion.
,但是我们很难,像描述不可逆膨胀一样,来描述不可逆压缩。
it becomes a gray area but it should be pretty clear if you can treat something is reversible are irreversible.
这是个灰色区域,但什么可以当作可逆过程处理,而什么要当作不可逆过程,这是相当清楚的。
Now,that thing that wakes up after this complete irreversible amnesia will no doubt eventually develop a personality,a set of beliefs,memories.
这人在经历了完全不可逆的失忆后醒来,最终发展出了自己的人格,信念和记忆。
You've irreversibly changed that substance because you've changed the structure of all the proteins inside.
蛋白质的结构发生不可逆的变化,因为蛋白质内部的全部结构都改变了
Anybody have any questions on that, because when we voted, the majority of the class thought it was reversible Yes.
上节课我们投票时,多数人都认为它是一个可逆过程,而现在大家应该都知道了,它其实是不可逆过程,有问题吗?
I mean we can, we can sort of understand why OK, the total energy, if we measure it, we measure a process which is not reversible.
例如我们易于理解为什么,当试图测量一个不可逆系统的总能量,给出的或许。
Instead of this reversible isothermal step, Let's make it an irreversible isothermal step.
不是可逆等温过程,而是不可逆等温过程。
get back to the initial point is going to require some input from outside, like heat or extra work or extra heat or something because you've done an irreversible process.
如果要逆转它,回到初始点,就需要外界的投入,比如额外的功,额外的热量等等,因为你进行了一个不可逆过程。
Now, if we go back to our Carnot cycle which is a set of reversible paths, it's useful to compare this to what happens in an irreversible case.
如果回到卡诺循环,它是由一系列可逆过程组成,我们将它,和不可逆过程的情况相比较。
That's why we always talk about irreversible expansion, because it's easy to write down an irreversible expansion.
这就是我们总是,讨论不可逆膨胀的原因,因为它,比较容易描述。
And all we know about this is that it's really for some irreversible reversible step.
我们知道,这个式子,对不可逆过程成立。
You have to do it awfully fast to get your irreversible compression.
我们要压缩得非常快,才能实现不可逆压缩。
OK, so now we're going to do the same kind of experiment, but irreversibly. An irreversible adiabatic.
现在来在,不可逆的条件下,完成相同的实验。
And I want to make sure everybody figured out that it really was an irreversible expansion.
或者多孔塞的,不可逆的等焓过程。
that instead of all the steps being reversible, let's just put in one irreversible step.
不是所有的过程都是可逆的,其中有一个过程不可逆。
We can do it reversibly, or we can do it irreversibly.
它可以是可逆的,也可以是不可逆的。
So w, the work is less for the irreversible process than the reversible process.
不可逆过程中系统对外界,做的功要比可逆过程时小。
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。
If it was non-reversible, I would be allowed to put an initial point and a final point, but I wouldn't be allowed to put a path between them like this, connecting them together.
如果是不可逆过程,我可以画出过程的初态点,和末态点,但是我不能再像这样,画出连接这两个点的,路径曲线来。
STUDENT: .
学生:不可逆压缩也可以:,通过快速的压缩实现吗?
No, pretty much things are either reversible or irreversible.
不,几乎所有的都是要么可逆,要么不可逆。
Wirr Minus w irreversible, this is the work which is done to the environment by the system, -Wrev minus w irreversible is always smaller than minus w reversible.
一点提示,不可逆过程中系统,对外界做的功,总是小于,之前我们。
Like something is almost reversible and almost irreversible.
就像什么东西是几乎可逆的,或几乎不可逆的。
So suppose we do it irreversibly.
假设它是不可逆的。
STUDENT: Is there a boundary between reversible and irreversible?
学生:可逆与不可逆间,有没有边界?
du But if it's not reversible, it's not du.
但如果这不是可逆过程,它不等于。
We're going to also look at the irreversible case briefly.
以后我们会简单地讲下不可逆过程。
Now, you all know that we can make irreversible changes in proteins, you can denature them completely, that's what happens when you cook an egg for example.
现在你们都懂蛋白能够发生不可逆的改变,能够完全变性,比如在你煮鸡蛋的时候就是这样
Because if it's irreversible, it's very likely that I don't know what the pressure inside the system is doing while this is happening.
因为对不可逆过程,系统内部的压强,没有明确的定义,气体不处于平衡态。
So now let's look at the efficiency of our irreversible engine.
再来看看,不可逆热机的效率。
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