It turns out that this quantity here, which is called eta of J the Joule free expansion parameter, is not quite zero.

这个量后来被，称作焦耳膨胀系数,其实并不等于零。

麻省理工公开课 - 热力学与动力学课程节选

So this is a very small number and for ideal gases, eta J is equal to zero.

这是一个，很小的数。

麻省理工公开课 - 热力学与动力学课程节选

Right now we told you Joule did all these experiments and he found out that for an ideal gas, that the limit in and ideal gas 0 case was that the eta J was equal to zero.

现在我告诉你们焦耳,做了所有这些实验,他发现对于理想气体,在极限情况下理想气体的ηJ等于。

麻省理工公开课 - 热力学与动力学课程节选