Delta v is positive in this direction here, the work is negative. So work on the system is positive. Work done by the system is negative.

功是负的，总而言之,外界对系统做功的符号为正。

麻省理工公开课 - 热力学与动力学课程节选

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。

麻省理工公开课 - 热力学与动力学课程节选

And so, we can rewrite this as the work nRTln is equal to minus nRT log p1 over p2, nRTln or nRT log p2 over p1.

因此我们可以把这个式子改写一下,功等于负的，或者。

麻省理工公开课 - 热力学与动力学课程节选

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。

麻省理工公开课 - 热力学与动力学课程节选

V Minus p2, V2. Minus p delta V. So the total work is the work from the left hand side plus the work on the right hand side, p1 V1- p2 V2 which is p1 V1 minus p2 V2.

负p2V2【w=-p2v2】，即负pΔ,所以全部的功就是,左边的功加上右边的功，等于。

麻省理工公开课 - 热力学与动力学课程节选