Well, it turns out we can do the same thing in space and that is called Stokes' theorem. What does Stokes' theorem say?

我们发现，在空间里面也可以做一样的事情，那是Stokes定理，Stokes定理说了什么呢？

youdao

And that's why the flux for S1, and the flux for S2 were the same a priori and we didn't have to worry about which one we chose when we did Stokes theorem.

这就是为什么S1的通量，和S2的通量是相同的，当运用Stokes定理时，我们不用担心，选的是哪一个面。

youdao

Well, the orientation I should have for Stokes theorem is that Well, if you look at the convention around here, it tells us that the normal vector should be going this way.

对于Stokes定理中的定向——，观察这里，它的法向量应该是这个方向。

youdao