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# Lecture on Capacitor knowledge(I)

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Characteristics of capacitors (intersecting).

A capacitor is a container in which charges are stored. It is made up of two pieces of metal close to each other, separated by insulating material. A variety of capacitors can be made according to the insulating material. Mica. Porcelain medium.Paper, Electrolytic capacitors, etc. In the structure, it is divided into fixed capacitors and variable capacitors. The capacitor has an infinite force on the DC resistance, that is, the capacitor has the function of isolating the DC. The resistance of capacitors to AC power is affected by AC frequency. That is, capacitors of the same capacity present different capacitive reactance to alternating current at different frequencies. Why do these phenomena occur? this is because the capacitor works on its charge-discharge function. As shown in figure 1, when the power switch s is not closed. Two plates of metal and other ordinary metal plates of capacitors are not charged. When the switch S is closed, as shown in fig. 2, the free electrons on the positive plate of the capacitor are attracted by the power supply and pushed onto the negative plate. Since the capacitor plates are separated by an insulating material, the free electrons running from the positive plate are stacked on the negative plate. The positive plate is positively charged by the reduction of electrons, and the negative plate is negatively charged by the gradual increase in the number of electrons. There is a potential difference between the two plates of the capacitor. When the potential difference is equal to the supply voltage, the charge of the capacitor stops.If the power supply is cut off, the capacitor can still maintain the charging voltage. . Until the potential difference between the two poles is zero. The discharge process of the capacitor is shown in Figure 3.The AC frequency applied to the two plates of the capacitor is high. Capacitors have reduced resistance to high-frequency alternating current, ie, small capacitive reactance. On the contrary, the capacitor has a large capacitive reactance to the low frequency alternating current. For the same frequency AC power. The larger the capacity of the capacitor, the smaller the capacitive reactance and the smaller the capacity, the larger the capacitive reactance.