They passed through the archway and the chair-bearers paused to change the pole from shoulder to shoulder.

他们穿过拱门， 抬椅的人停下来把杆子从一个肩膀换到另一个肩膀。

You can't change the north and south poles on these magnets, but as we now know, for electromagnets, we can change these poles by changing the direction of the electrical current.

你无法改变这些磁铁上的北极和南极，但正如我们现在所知，对于电磁体，我们可以通过改变电流的方向来改变这些磁极。