You've got a magnetic field, maybe even magnetic susceptibility, the electric field. We're not going to worry about these magnetic fields or electric fields in this class So, pretty much we're going to focus on this set of variables here.

你也会引入磁场，或许甚至磁化率，以及电场，我们这堂课不需要关心,这些磁场或,电场之类的东西,基本上我们只关注,这里的一组变量。

麻省理工公开课 - 热力学与动力学课程节选