??(1) Capacitors can store charge and have the function of blocking DC

??When the two plates of the capacitor are respectively connected to the positive and negative electrodes of the DC power supply, the positive and negative charges will accumulate on the two electrode plates of the capacitor, forming a voltage between the two plates. With the continuous increase of the charge on the two plates of the capacitor, the voltage on the capacitor gradually increases from small to small. When it is equal to the DC power supply voltage, no current will flow in the circuit and the charging process will stop. This is the charging of the capacitor. effect. If the DC power supply is disconnected from the capacitor, then the capacitor will store charge. The amount of charge stored can be calculated by the following formula. It can be seen from the above formula that when the voltage across the capacitor is constant, the capacity of the capacitor will increase. Larger, the greater the amount of charge it stores. It can be seen that the capacitance of a capacitor is a parameter that measures the capacity of a capacitor to store charges.

??After the charge is stored on the capacitor, since the two plates of the capacitor are separated by the insulating medium, although there is voltage at both ends of the capacitor, the charge cannot pass between the electrodes, so the capacitor has the function of blocking direct current.

??If the two electrodes of a capacitor with stored charges are connected with wires, at the moment of connection, the positive and negative charges on the capacitor plates will be neutralized by the wires, which is the discharge effect of the capacitor. The process of capacitor discharge is a process of energy release, which will do work in the discharge circuit to convert electrical energy into other types of energy.

??When a capacitor is used in an electronic circuit, if the voltage on the electronic circuit is higher than the voltage across the capacitor, the capacitor is charged until the voltage established on the capacitor is equal to the voltage of the circuit; if the voltage on the electronic circuit is lower than the voltage across the capacitor , The capacitor is discharged.

??(2) Alternating current can "pass" the capacitor
If the capacitor is connected to an AC circuit, the capacitor will be charged alternately and discharged repeatedly due to the constant changes in the magnitude and direction of the AC voltage. At this time, there is still no charge between the two plates of the capacitor, but it is formed in the AC circuit. The AC current that keeps changing in direction and size is just like a capacitor can pass AC power. This is the reason that AC can "pass" a capacitor.

??(3) Capacitive reactance of capacitor
??Capacitors have special resistance characteristics to alternating current, called capacitive reactance. The capacitive reactance can be calculated by the following formula, that is, it is not difficult to see from the above formula that the larger the capacity of the capacitor, the higher the frequency of the current, the smaller its capacitive reactance, and the easier it is for AC current to pass through the capacitor.