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But,many of the harmful effects of smoking ARE reversible.
VOA: special.2010.03.09
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Of course in the reversible case, you're always pushing against an external pressure, which is essentially equal to the internal pressure.
当然在可逆的情况下，外压力，总是，等于内部压力。
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So for the reversible process, the work done is the integral under the pressure volume state function, the function of state.
对可逆过程，做的功,是压强体积态函数曲线下，的积分面积。
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it was reversible, so you can give people money and take it away, and you could actually scale the amount of money, so it makes a very handy experimental tool.
这个过程是可逆的，这样你可以给人钱，然后拿走，而且你还可以积攒钱，这就让钱成为了一种非常有用的试验工具。
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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。
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we're going to have a difference here between the irreversible case and the reversible one.
可逆过程,和不可逆过程,会有不同。
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The reversible process is going to be colder because it has to expend more energy.
可逆过程降温更多,因为输出的能量更多。
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It's really important that this, that you remember that this is the reversible case.
一定要记住，整个过程是可逆的。
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In a real engine, of course, you can approach the reversible limit.
在一个真实的热机里，当然，你可以达到可逆极限。
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So it's that the irreversible efficiency is lower than the reversible one.
所以不可逆过程的效率,小于可逆过程的效率。
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It would be equal for the reversible case.
等号成立。
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That's equivalent to doing the integral, and so, what we end up getting is that the reversible work v2 pdv is equal to minus integral V1, V2, p dV.
这与刚才的积分过程效果相同，最后，我们得到的结论是可逆过程的功,是负的积分，从v1到。
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Because it's so important. And I should add and also under reversible work, where the external pressure is equal to the internal pressure.
而且我还要说应该在外部压强,和内部压强相等的,可逆过程中引入它。
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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？
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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。
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So what this says is the efficiency of any reversible engine T1 has to be one minus T2 over T1.
这就是说,任何可逆热机的效率都是,负T2除以。
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One is our Carnot engine as we've seen it, and the other is just any other reversible engine.
一个是我们已经学过的卡诺热机，另一个是任何一个其它可逆热机。
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And what you'll find is that the maximum work out is obtain for a reversible path.
对于各种可能的中间路径，我们将发现,做功做多的是可逆路径。
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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。
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That is, this is derived in the case for reversible paths.
即这些都是通过利用可逆过程推导出来的。
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Only in the case of reversible processes.
只有在可逆过程中。
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So we're going to start at one, T1 and this is going to be in isotherm at temperature T1, and all the paths here are going to be reversible.
我们从一开始，这是个绝热恒温过程，温度是，所有路径都是可逆的。
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As long as it's reversible, you know what the efficiency has to be, and in principle, you could break it down into a bunch of steps that you could formulate as isothermal and adiabatic.
只要这个循环过程是可逆的，你们知道效率是多少，从理论上说，可以将总过程,分解成一系列绝热,和等温的小过程。
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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。
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But you don't compress it so quickly that you're not in there reversible process so you compress that if you were to feel the temperature of the air and you can feel it through the nozzle gives you an idea of the temperature of the air inside your bicycle pump.
但是压缩速度,也不能太快,否则就不是,可逆过程了,这样当压缩气体时,从喷嘴可以感受到,内部气体的温度。
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TdS It comes from the fact that dq reversible is T dS, pdV and dw reversible is minus p dV.
这个结论来自于：可逆过程下dq等于，做功dw等负的。
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if it's a reversible process then the equality holds, but if it's irreversible, which means it happens spontaneously, T then dS is greater than this.
对于可逆过程，等号成立，但是如果是不可逆过程，这些不可逆过程是自发进行的，那么dS大于dq除以。
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Remember it's the external pressure that's important. In this case, because it's a reversible process, the external pressure turns out to be always the same as the internal pressure.
是过程非常缓慢,比如我把体积，从V1压缩到V2时，我做得十分缓慢,在过程中的任何一点。
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If it's a reversible process, we know the work is the area under the curve.
对可逆过程，功等于p-V图上。
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Adiabatic q equal to zero. It's also delta H 0 which is zero. The two didn't necessarily follow because remember, delta H is dq so p is only true for a reversible constant pressure process.
在这个过程中ΔH等于,绝热的所以q等于0，而ΔH也等于,这两个也不一定有因果关系,因为，记住，ΔH等于dq只有在恒压。
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