"If you see a number of scores on a hundred point scale on the 40,50,60 range that suggests that people are moving back and forth.

VOA: standard.2010.02.25

Because there are ions moving back and forth, there's a current that flows and there's a electrical potential that's generated.

由于离子的进进出出,就产生了电流流动,并且形成了电势差

耶鲁公开课 - 生物医学工程探索课程节选