Direct current: Electricity whose voltage magnitude and direction do not change with time is called direct current.
Alternating current is mainly 220V for civil use and 380V for industrial use, while direct current is generated by dry batteries and storage batteries.
Main differences:
1, the direction of positive and negative poles of alternating current is uncertain, and it changes periodically at all times. For example, 220V, 50Hz AC commercial power for civil electricity, 50 cycles per second, alternating positive and negative directions 100 times;
2. The voltage and current of alternating current change periodically, and there is a zero-crossing moment similar to the period of alternating current, and there is no current in the circuit at the zero-crossing moment or it tends to infinity;
3. When alternating current passes through inductive load, self-inductance will occur. The transformer made by electromagnetic induction principle can easily change the voltage of alternating current (it can step up and step down and can be used as equivalent isolated output);
4. Alternating current uses the principle of electromagnetic induction and transformer to carry out different power distribution and line impedance matching, so that each circuit can obtain different corresponding power and ensure that each part is independent and does not affect each other;
5. Alternating current with proper frequency and voltage (especially three-phase alternating current) can have a special effect on inductive load (or capacitive load), and even directly make the three-phase induction motor run effectively.