These are physical knobs that are available us as experimentalists. And so when we turn these knobs on our system, we want to know how the enthalpy is changing for that system.

这些都是我们做实验可,以得到的物理变量,所以当我们在系统中,改变这些量的时候。

麻省理工公开课 - 热力学与动力学课程节选