1. The magnitude of the current varies. The size of AC current varies periodically, while the size of DC current is fixed and will not change.
2. Different uses of current. AC power is generally used in circuit breaker, air switch and power circuit transmission. DC power is commonly used in electronic instruments and electric drive.
3. The direction of the current is different. The direction of the alternating current is not fixed and will change with the change of the cycle. For direct current, the direction of direct current is fixed, and from positive to negative.
4. Difference in current characteristics. There is a zero point in the AC current, and the voltage wave will produce a positive or residual spiral wave, so the corresponding arc extinguishing equipment can be used for circuit opening and closing. However, DC has no zero crossing property, so it is impossible to make a circuit breaker.