Views:74 Author:Site Editor Publish Time: 2019-09-17 Origin:Site
Power supply is a device that converts other forms of energy into electrical energy. Today we will introduce DC power supply, AC power supply and their differences.
Direct Current (DC) is also known as "constant current". Constant current is a kind of direct current, which is constant in size and direction. It was discovered by Edison. In 1747, Franklin of the United States proposed the law of conservation of charge based on experiments, and defined the terms of positive and negative electricity.
The circuit through which direct current passes is called direct current circuit, which is a closed conductive circuit composed of direct current power supply and resistance. 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 resistance. In the power supply, the non-electrostatic force of the power supply is used to overcome the electrostatic force, and then from the low potential to the high potential, so that a closed current line is formed. Therefore, in DC circuit, the function of power supply is to provide constant electromotive force which does not change with time, and to supply energy for Joule heat consumed on resistor.
Alternating Current (AC) refers to the alternating current whose direction changes periodically with time, and the average operating value is zero in a period. Unlike direct current, its direction will change with time, and there is no periodic change in direct current. When electromagnetic induction is discovered, the method of generating alternating current is known. Early products were developed by British Michael Faraday and French Hippolyte Pixii.
Usually the waveform is a sinusoidal curve. AC can effectively transmit electricity. But in fact, there are other waveforms, such as triangular wave and square wave. The municipal electricity used in daily life is AC power with sinusoidal waveform.
DC transmission loss is large, so it is not suitable for long-distance transmission, AC transmission loss is small, so it is suitable for long-distance transmission.
DC voltage is stable, no white noise, so it is suitable for the use of electronic products (such as television, radio, computer, etc.) AC has to be converted into DC through rectifier/switching power supply to supply electronic products.
(a) Measuring with digital universal meter, using 20V AC voltage and 20V DC voltage, the results will be different.
(b) Simple measurement method: put the induction pen (non-ordinary pen) outside the wrapping of the wire, 12V AC will still display, 12V DC will not display.
12V DC is safer to human body than 12V AC. When the resistance of human body decreases, 12V AC may still electrocute people. 12V DC will not electrocute people in 100% of cases.
The pattern of direct current (voltage) is a straight line (frequency is 0 Hz), the voltage is constant (ideal situation), the voltage pattern of alternating current is sinusoidal curve, and the voltage is periodic, which is different at every moment. The frequency is 50 Hz (domestic) or 60 Hz (foreign), but the bulb is not sensed by the naked eye.
When power is supplied to a resistive load (lamp), it seems that the power formula of current formula is the same and there is no difference. When power is supplied to a non-resistive load (motor, etc.) refer to the above two answers (as if the current power formula is different, and the frequency and other variables are added to the alternating current).
If you want to transmit data on the wires (such as the intelligent control system of the home building abroad), only AC is suitable, and DC is also possible. But there is basically no research on DC at home and abroad (because of the transmission loss of DC, the idea of additional data is basically abandoned).
According to the voltage pattern, the instantaneous peak voltage of 12V AC/DC is different. The instantaneous peak voltage (12V DC)12V and the instantaneous peak voltage (12V AC)= √2 *12V.
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