Direct current only flows in one direction at short distances at one voltage, whereas alternating current flows in multiple directions and can reach longer distances and the voltages can be stepped up or stepped down.

直流电在一个电压下只能在短距离内沿一个方向流动，而交流电则在多个方向上流动并且可以到达更远的距离并且电压可以升压或降压。