In resistance, the flow of electrons is proportional to the voltage drop. so what happens when alternating current (AC) is applied to the capacitor?

　　What happens when alternating current (AC) is applied to the capacitor? capacitance behavior is different from resistance —— in resistance, the flow of electrons is proportional to the voltage drop; in capacitance, when it is charged or discharged to a new voltage level, it resists voltage changes by absorbing or releasing current.


　　When providing direct current (DC) to a capacitor, as long as the supply voltage exists, it is charged to the value of the added voltage like a temporary energy storage device and then holds or maintains this charge indefinitely. If there is any change in voltage, there will be a charge current in the capacitor to resist this change, and the rate is equal to the rate of change of charge on the capacitor plate.

　　As shown in the figure, the following studies only have capacitors and AC power circuits. It is proved that there is a phase difference of 90 between the current and the voltage, and the current reaches the peak value 90(1/4 period). The AC power supply will produce oscillating voltage, the larger the capacitance value, in order to establish a specific voltage on the plate, the more charge must flow, so the larger the current. The higher the voltage frequency, the shorter the time available to change the voltage, so the current must be larger. Therefore, the current will increase with the increase of capacitance and frequency.


　　Capacitive AC circuit

　　Pure capacitive AC circuits are circuits that contain only AC power and capacitors, as shown in the figure. The capacitance is directly connected to the two ends of the AC power supply voltage. With the increase and decrease of the power supply voltage, the capacitance will be charged and discharged. The current will flow through the circuit first in one direction and then in the other, but the capacitance actually has no current flowing through it. The electrons accumulate on a polar plate and then drain quickly and continuously from one plate, giving the impression that the current flows through the insulator of the polar plate.


　　capacitive reactance

　　The current flowing through the capacitor is proportional to the rate of change of the voltage at both ends of the capacitor. The capacitive reactance in the pure capacitor circuit hinders the current in the AC circuit. Because, like resistance, the unit of measurement of reactance is Om, so in order to distinguish it from pure resistance, reactance is represented by symbol X. since the capacitive reactance depends on the value of the capacitance (in farah), and the frequency of the ac waveform, it can be represented by the following formula.

　　The formula shows that if the frequency or capacitance value is increased, the total capacitive reactance will decrease. similar to the ideal conductor, the capacitive reactance of the capacitor will decrease to zero when the frequency is close to infinity.

　　How does the capacitor work in the AC circuit?Do you know now？Get in touch if you would like to make some serious savings on your electrical products and RF connector！