We have discovered that this partial derivative that appears in the definition, the abstract definition of the differential for internal energy, is just equal to the constant volume heat capacity.

我们还发现,这个偏微分出现在了，内能的偏微分,定义式中，它也就是热容。

麻省理工公开课 - 热力学与动力学课程节选

And because there is an explicit relationship between u, delta u, q and w, you can always find the easy way to derive the change in internal energy or the heat or the work.

因为Δu，q和w之间,有明确的关系，一般来说,内能或热或功的变化,易于计算。

麻省理工公开课 - 热力学与动力学课程节选