Let's look at a circuit with only an alternating voltage source and a capacitor.

让我们看一个只有交流 电压源和电容器的电路。

In this case, current leads voltage by 90 degrees, changing the direction ahead of the voltage source.

在这种情况下，电流超前电压 90 度，改变了电压源前面的方向。

Typically, the voltage source in a DC circuit is unchanging, so the current will be constant, too.

通常，直流电路中的电压源是 不变的，因此电流也是恒定的。

So when the voltage changes from positive to negative, the capacitor acts as a smaller voltage source that still pushes the current along.

因此，当电压从正变为负时，电容器充当较小的电压源，仍然推动电流前进。