Microscopic Electric Current微观电流
Since electric charge is quantized in discrete multiples of the electron charge, it is instructive to look at electric current as the movement of multiple microscopic charge carriers with a drift velocity in a conductor. 由于电荷以电子电荷的离散倍数形式量化，将电流视为导体中多个微观带电粒子以漂移速度运动是很有启发性的。
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Electric Charge Carriers电荷载体
For electric current in a copper wire, the charge carriers are the mobile electrons and the positively charged copper ions are essentially stationary in the metal lattice. Nevertheless, treatments of electric circuits usually use conventional current, as if positive charges were moving. Debate continues about this practice, but the physical nature of the charge carriers in copper is fairly straightforward. 在铜 wire 中的电流，电荷载体是自由电子，而正电荷的铜离子在金属晶格中基本上是静止的。然而，电路的处理通常使用 conventional 电流，仿佛是正电荷在移动。对此做法仍存在争论，但铜中电荷载体的物理性质相对明确。
In other applications of electric current however, the identification of the charge carriers is not so simple. In semiconductors, for example, you sometimes have electrons which are mobile, and sometimes have deficiencies of electrons, called "holes" which are mobile. There are significant differences in the way they conduct. One way to detect which kind of conduction is taking place is with the Hall effect, which gives a different polarity for the Hall voltage for positive and negative charge carriers. In many substances, electric conduction is not just free electron movement. 然而，在其他应用中，电电流的载流子识别并不那么简单。在半导体中，例如，你有时会遇到可移动的电子，有时也会遇到电子的缺乏，称为‘空穴’，这些空穴也是可移动的。它们的导电方式有显著差异。一种检测正在发生哪种导电方式的方法是霍尔效应，它会因正负载流子而给出不同的霍尔电压极性。在许多物质中，电导并不是仅仅由自由电子的运动所决定的。
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Drift Velocity of Charge Carriers电荷载体的漂移速度
Although your light turns on very quickly when you flip the switch, and you find it impossible to flip off the light and get in bed before the room goes dark, the actual drift velocity of electrons through copper wires is very slow. It is the change or "signal" which propagates along wires at essentially the speed of light. 尽管你翻转开关时灯很快亮起，而且你发现很难在房间变暗之前关灯上床，但电子通过铜线的漂移速度却非常缓慢。实际上，是‘信号’以接近光速在导线中传播。
The drift velocity of electrons in a copper wire can be calculated from 铜导线中电子的漂移速度可以从
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Density of Charge Carriers电荷载体密度
Calculation of the density of free electrons in a metal like copper involves the basic physical data about the metal, plus the fact that copper provides about one free electron per atom to the electrical conduction process. A representative value can be calculated with the following data. 计算铜等金属中自由电子的密度需要金属的基本物理数据，以及铜每个原子提供约一个自由电子参与电导过程的事实。可以利用以下数据计算出一个代表性值。
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