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the total amount of the work that we can get out is just given by the area inside this curve.
能够输出的功就是,我们可以得出来,曲线所包围的面积。
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And the idea was that gravity did work on the water and falling, and that work led to the generation of heat.
焦耳的想法是,重力对水，做了功。
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The virtual work of the reader does not involve surprise, does not involve the violation of expectations.
读者的虚功中没有惊讶，也没有期望的违背。
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Gas phase single atom. So we don't have to deal with work function or any kind of energies associated with some condensed form of matter.
气相的单原子，所以我们不需要再,处理功函数的问题,以及和凝聚态相关的能量问题。
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Sometimes we might just directly tell you that's probably the easiest scenario, because when we think about work functions those are usually reported in energy.
有时候我们可能只是直接告诉你,那可能是最简单的情况，因为当我们考虑功函数时,它们经常用能量来记录。
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Where have we implemented a greedy algorithm, or have been asked to do a greedy algorithm? Well, there are not that many things you guys have been working on this semester.
现在你已经实施了一个贪婪算法,我们在哪里实施了贪婪算法,或者我们那里被要求实施贪婪算法呢？,们这学期不需要用什么功对吧？
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And we combine this with first law, which for the case of pressure volume changes we write as this.
结合第一和第二定律,对于压强体积功我们可以这样写。
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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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And in practical terms, we can define the efficiency as the ratio of the heat in to the work out.
在实际中，我们定义,效率为热与功的比值。
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Because we did work at constant pressure, and so it's just volume difference times pressure.
因为是在恒压下做功，所以功就等于体积变化乘以压力。
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Now in order to illustrate the way in which what Iser calls virtual work gets done in this regard, let me just run through a few passages quickly.
现在，为了阐释,在这点上，伊瑟尔所说的虚功是怎样做的，下面我们来快速地浏览几段话。
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Wrev w reversible. in this case here let's see this is it's a pressure is going down.
曲线下的面积，可逆过程的功,这个过程中。
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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。
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So, it's a trivial matter, by looking at what is the weight and how far does it drop, to say OK, how much work is done by the paddle wheel.
好，让我们看看重物的质量,以及它下落的距离，就知道桨轮做了多少功。
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So the maximum work out required the maximum heat in.
因此输出最大的功要求,有最大的热。
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That's the work that the system is doing to the environment. I'm doing work to the environment. The work is negative, which means that work is being done to the environment.
功的大小,就是矩形的面积,这样我们就实现了一台热机，冷却，加热，加热,冷却，系统回到了初态。
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Let's divide it up into the two sides, the work going on on the left hand side, my left hand side or your left hand side, and the work going on on the right hand side.
仅仅是功的大小而已，让我们把它分成两部分，左手边功的变化，和右手边功的变化。
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After all, we're taking the output work that we get from the right, and using it all to drive the left.
毕竟，我们利用,右边产生的功，来驱动左边的热机。
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So again, for both heat and work we don't get the same result. Now let's look at our special function, right. So here's path A.
所以，再一次说明，对于热量和功,我们得到的结果是不同的,现在让我们看看我们的特殊函数。
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W1 So I have my initial state, my final state, W1 my initial state, my final state here.
再加热，做功，对系统做的总功是。
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This piston is being brought out, so we expect 0 the work to be negative, negative. And we start o V2 ut with zero volume. We end up with a volume p2 of V2, and the external pressure is constant to p2.
所以我们可以想象功是负的,开始的时候体积是,最终的容积是,外界的压力恒为。
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We're going to find other properties that do care about the history of the system like work, that you put in the system, or heat that you put in the system, or some other variables But you can't use those to define the equilibrium state.
我们还会发现其他一些,与系统的历史有关的性质,比如你对系统做的功，或者你向系统传递的热量，或其他的变量,但你不能用它们,来定义平衡态。
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W2 If I go backwards, to work p1 becomes the negative from what I had p2 calculated before, so this becomes minus what I calculated before for w2.
应该是,总功等于,减去,等于。
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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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So, we do this here for the photoelectric effect, and in terms of the photoelectric effect, what we know the important point is that the incoming photon has to be equal or greater in energy then the work function of the metal.
所以，我们做这个是为了说明，光电效应，在光电效应方面，我们知道的最重要的事情,就是入射的光子能量必须等于,或者大于金属的功函数。
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Now we know we're going to get less work out of it in that case.
我们知道,这样的话得到的功会变少。
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And the work in this case is the area inside here.
现在的功是这个区域内部的面积。
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So if we think about the work function for zinc, and the work function for zinc is 6.9 times 10 to the -19 joules, do we expect that when we shine our UV light on the zinc, we'll be able to eject electrons?
如果我们考虑锌的功函数,它是6，9乘以10的-19次方焦耳，我们是否可以预测当,用紫外灯照射锌时，我们可以射出电子呢？
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When we talked about the photoelectric effect, that was called the work function.
如果我们在研究光电效应，这被称为功函数。
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But it's a good story, Joule decided that there must be a direct relationship between work and heat.
所以说，这只是一个不错的故事而已，焦耳认为功和热之间,一定具有某种直接的联系。
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