What is the difference between AC and DC?

What is the difference between AC and DC ？

There are two forms of electricity —— Alternating current (ac)  (AC) And DC （DC）

1. What is AC power ？

Alternating current (ac) （AC） The power supply is the standard power output from the power outlet , Is defined as a charge flow that exhibits periodic directional changes .

Because of the electron , The current of alternating current varies between positive and negative  - The current comes from the flow of these electrons , These electrons can be positive （ Up ） Or negative （ Down ） direction . This is called a sinusoidal AC wave , This wave is caused when the alternator in the power plant produces alternating current .
An alternator generates alternating current by rotating a loop in a magnetic field . When the wire moves to the area of different magnetic poles , Will generate AC waves —— for example , When the wire rotates from one pole of the magnetic field to the other , The current changes direction . This wavy motion means that alternating current can travel farther than direct current , This has a huge advantage in supplying power to consumers through power outlets .

2. What is DC power ？

Direct  (DC) Power Supply , seeing the name of a thing one thinks of its function , Is a linear current —— It moves in a straight line .
Direct current can come from many sources , Including batteries 、 Solar cell 、 Fuel cells and some improved alternators . By using a rectifier that converts alternating current to direct current , It can also be switched from an alternating current “ manufacture ” Direct current .

DC power supply is more consistent in terms of voltage transmission , This means that most electronic devices rely on it and use DC power such as batteries . Electronic devices can also use rectifiers that are usually built into the power supply of the device to convert AC from the socket to DC . The transformer will also be used to raise or lower the voltage to a level suitable for the equipment in question .
however , Not all electrical equipment uses DC power . Many devices 、 Household appliances , Especially lamps 、 Washing machines and refrigerators, etc , All use alternating current , AC power is transmitted directly from the power grid through the power socket .

3. What do the two different power supply types need ？

Although many electronic and electrical equipment today prefer DC power supply because of its smooth flow and uniform voltage , But if there is no alternating current , We can't survive . Both of these powers are indispensable . One is no better than the other “ Better ”.

in fact , AC dominates the electricity market . All power outlets supply power to the building in the form of alternating current , This is true even where it may be necessary to convert current to direct current immediately . This is because direct current cannot travel the long distance from a power plant to a building like alternating current . Because of the way the generator rotates , It is much easier to generate alternating current than direct current , And the system is generally cheaper to run —— Use alternating current , Electricity can be easily transmitted through the national grid through several kilometers of wires and towers .
DC Mainly play a role , The device needs to store power in a battery for future use . A smart phone 、 laptop 、 Portable generator 、 Flashlight 、 Outdoor CCTV camera system …… You can think of it , Anything powered by batteries depends on storing direct current . When the battery is charged from the main power supply , The alternating current is converted into direct current through a rectifier and stored in a battery .

however , This is not the only charging method used . for example , If you have ever used mobile power to charge your mobile phone , Then you use DC power instead of AC power . In these cases ,DC-DC The power supply may need to change the output voltage （ In this case, the mobile power supply ） For equipment （ In this case, the mobile phone ） Use .