In a conductor like copper metal, electrons flow through the entire material.

在如同金属铜一类的导体中，电子会流过整块金属。

This electron flow is the electric current which is the reason for the battery's existence.

这种电子流就是电流，这就是电池存在的原因。

However, just by reversing the polarity of the electron flow, if you will, we can create a very different situation.

然而，通过改变电子的流向，如果你愿意，我们就可以创建另一种情况。

Electrons flow from high to low voltage.

电子从高电压流向低电压。

An engine, for example, can be powered by direct current – which means that the electrons flow in one direction only.

例如，一台发动机，可以由直流电提供动力，这意味着电子仅在一个方向上流动。

In conductive materials, electrons flow around atoms, forming an electric current.

在导电材料中， 电子围绕原子流动，形成电流。

Well in each sensor we have a very small plate of metal or  semiconductor with electrons flowing across it.

在每个传感器中，我们都有一个非常小的金属板或半导体板，电子在它上面流动。

An LED is a type of diode or semiconductor device that emits light when electrons flow through layers of crystalline inorganic material.

LED 是一种二极管或半导体器件，当电子流过结晶无机材料层时会发光。

But if I asked you why there are electrons flowing from one metal to the other, there's a fairly good chance that you would either be stumped, or you would be wrong.

但是如果我问你为什么会有电子从一个金属传递到另外一个金属，你们很有可能会被问倒了，或者是会回答错误。

When a bunch of metal atoms come together in a chunk, these outer electrons wiggle free, creating what scientists usually think of as a negatively-charged “sea of electrons” flowing around a network of positively-charged ions.

当大量金属原子聚集结合为块状，这些外层电子自由移动，就产生了科学家通常所说的电子海，即大量带负电荷的电子游荡在带正电的金属阳离子周围。