"I must call Mister Behrman up to be my model for my drawing of an old miner.

VOA: special.2009.08.01

So this is a little bit negative and this is a little bit positive, which means I could model this by drawing a dipole. This is a dipole.

这边带一点负电,这边带一点正电，这意味着我能把它表示,成一个偶极。

麻省理工公开课 - 固态化学导论课程节选