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。

麻省理工公开课 - 热力学与动力学课程节选

And of course, in either case, w delta u is q plus w, so it's q irreversible plus w irreversible, u being a state function it's the same in either case.

当然了，在这两个过程中，Δu都等于q加，因此现在是q不可逆加w不可逆，同时u在这两个过程中都是态函数。

麻省理工公开课 - 热力学与动力学课程节选