The difference between AC and DC

Place the head of a battery (positive) against the tail (negative) of the other section in the flashlight, and the flashlight is on: the flashlight is off if it is upside down, head-to-head, or tail-to-tail. This is because the current generated by the battery is always in one direction, so-called DC.

The electricity that is fed home through a power line or cable is not direct current but alternating current. Because this current flows in a direction for a while, then in the opposite direction for a while.

Despite the "diversity" of AC, one of the biggest advantages over DC is the ability to use transformers to raise or lower the AC voltage as needed. Because of the electricity produced by power plants, have to be transported far away for users to use. The higher the voltage, the smaller the loss during transport. When the voltage rises to 35,000 or 220,000 volts, even up to 500,000 volts, it is more economical to transport. No matter where you want to use electricity, in order to meet its specific use, they have to reduce the voltage. For example, household electricity as long as 220 volts, while the factory commonly used 380 volts, and so on.

DC also has its advantages in the chemical industry, such as electroplating, it is necessary not to DC. Start the tram, it is better to use DC.

In order to adapt to the specific use of various appliances, but also the AC into DC, called rectification. Some semiconductor radios or tape recorders are available external power supply. Through a square-shaped device, the AC into direct current to use. This step-down and rectifier device called the power converter.

General comparison:

1, AC is the size and direction are cyclical changes over time. DC is the same direction.

2, there is no positive and negative AC, DC positive and negative can not be exchanged.

Depth comparison:

1, DC transmission, the AC system on both sides do not need to run simultaneously, and AC transmission must be synchronized operation. When transmitting over long distances, the phase of the current creates a significant phase difference across the AC power transmission system.

2, the loss of DC transmission failure than AC transmission. If two AC systems are interconnected with AC lines, when a short circuit occurs on one side of the system, the other side must deliver a short-circuit current to the fault side.

3, In the cable transmission line, there is no capacitor current in the DC transmission, while the AC transmission line has the capacitor current, causing the loss.