" This difference, this energy difference between these two energy levels—from this we can extract how big, actually, the size of the nucleus is." Following this?

“这个差异，这两个能级之间的能量差异——从中我们可以提取出核的大小， 实际上有多大。 ” 接着这个？

And this drop in potential energy, divided by the test charge's magnitude, gives us the electric potential energy difference per unit charge, also known as the electric potential.

势能随着测试电荷量的减少给我们带来了差异 单次充电中的电势能，又称电势。