What Is the Difference Between Direct Current and Alternating Current?
Have you ever wondered why mobile phone charging plugs are larger than ordinary plugs?
In fact, strictly speaking, this "plug" is called a switching power adapter, and the purpose is to convert the alternating current from the power grid into direct current and transmit it into electronic equipment. Laptops have larger power adapters, making it easier to warm your hands in winter.
So why switch from alternating current to direct current? Let's start from the beginning!
* Learn about electricity first:
Electricity is a natural phenomenon. Static or moving electrical charges can produce interesting physical phenomena, such as the lightning you see during a thunderstorm, and the crackling sparks you see when you take off your sweater in winter. Later, scientists discovered laws from various electrical effects, so they invented batteries, generators, and motors.
* Should DC or AC be used first?
220V/50Hz AC is the power supply standard in my country, so many people think that household appliances use AC. As for direct current, I can't think of anything other than the "DC inverter air conditioner" that the advertisement will say.
A direct current is a current whose direction does not change with time.
An alternating current is a current that periodically changes in magnitude and direction.
* Alternating current or direct current, which is better?
As the line voltage continues to increase, the transmission power and transmission distance continue to increase, and direct current is favored by engineers. Because the direct current does not need rectification and filtering, there is no phase difference, and it is relatively stable.
From an economic point of view, although the cost of a DC converter station is higher than that of an AC transmission substation, the DC line only needs two positive and negative lines, and the three-phase AC line needs three lines, so the cost of the DC line is lower. Therefore, the longer the distance, the more suitable for DC transmission.
* Why do household appliances use direct current?
Returning to the field of household appliances, IT products (such as mobile phones, and computers) and most household appliances use DC power inside. Because notebooks and mobile phones are required to be light, the rectifier is placed outside. And desktop computers, refrigerators, air conditioners, etc. put the rectifier inside the appliance.
Why? Back to the essence, a direct current flows continuously from positive to negative, and the alternating current is fluctuating. Electronic components work by identifying high and low potentials.
For example, a computer has a potential of 1 and no potential of 0. The alternating current itself will have a zero-crossing potential, so electronic components cannot make correct logical judgments.
