DC (direct current) is a one-way flow or movement of charge, usually electrons. The current density varies with time, but usually the direction of movement is the same all the time. As an adjective, DC can be used for the reference voltage (its polarity never changes).
In a direct current circuit, electrons are formed from a cathode, a negative electrode, and a negative magnetic pole, and move toward an anode, a positive electrode, and a positive magnetic pole. However, physicists define DC as the motion from positive to negative.
Direct current is generated by electrochemistry and photovoltaic units and batteries. In contrast, in most countries, the current flowing from the device is alternating current (AC). The alternating current can be converted to direct current by a power supply consisting of a converter, a rectifier that blocks the flow of current in the opposite direction, and a filter that eliminates bounce in the current flowing out of the rectifier.
Virtually all electronic and computer hardware requires DC power to work. Most solid state devices require voltages ranging from 1.5 to 13.5 volts. The demand for current ranges from close to 0 in electronic watches to more than 100 amps required for wireless communication energy amplifiers. Devices that use vacuum tubes, such as high-energy wireless broadcast or television broadcast transmitters or cathode ray tube (CRT) displays, require approximately 150 volts to several thousand volts of direct current.
The loss of DC transmission failure is smaller than that of AC transmission. If two AC systems are interconnected by AC lines, when one side of the system is short-circuited, the other side must deliver short-circuit current to the fault side. Therefore, the ability to cut off the short-circuit current of the original switch on both sides of the system is threatened, and the switch needs to be replaced. In the direct current transmission, the circuit power can be adjusted quickly and conveniently due to the use of the thyristor device, and the short-circuit current is not substantially transmitted to the alternating current system on the direct current transmission line, and the short-circuit current of the fault-side alternating current system is not interconnected. Same time. Therefore, it is not necessary to replace the original switch and current-carrying equipment on both sides.
The circuit through which the direct current is passed is called a direct current circuit and is a closed conductive loop composed of a direct current power source and a resistor. In this DC circuit, a constant electric field is formed. Outside the power supply, the positive charge flows from the high potential to the low potential through the resistor. In the power supply, the non-electrostatic force of the power source acts to overcome the electrostatic force, and then reaches the high potential from the low potential, thus circulating, forming a closed Current line. Therefore, in a DC circuit, the role of the power supply is to provide a constant electromotive force that does not change over time, supplementing the Joule heat consumed in the resistor.