Why do capacitors store electric charge? Why is it AC resisted DC?

There are many types of capacitances, and complex capacitors are difficult to explain.

The most common capacitors are parallel-plate capacitors, which we have been exposed to in high school physics.

The capacitance of a parallel plate capacitor is proportional to the distance between the plates, inversely proportional to the opposing area, and proportional to the dielectric constant of the interplate dielectric. It can be vividly understood that under the dielectric constant of a certain medium, the volume of the space composed of the effective area of the two allegros determines the size of the capacitance.

The so-called capacitance is a measure of how much charge it can hold.

The so-called direct current is actually an electric current that never changes in size and direction, and as long as the current changes, it can be called alternating current. It can be simply explained that after the parallel plate capacitor is energized, one plate is positively charged, and the other plate is negatively charged (the charge is band on the inner surface of the plate, according to the surface effect of the charge), and the medium between the two allegros cannot make the two charges transfer and contact each other to complete the charge flow, otherwise, it will not be able to accommodate the charge, that is, it will cause the capacitance to break down, and the capacitor will be useless. In fact, it is mainly because there is no conductive material between the plates, so DC cannot be passed.

This is known as DC blocking.

As for the AC, the current changes, whether it is the direction or the size, it will produce the corresponding induced charge, whether it is more or less, that is, for example, a box of water, the volume of the box changes, it is bound to have some water overflow or dissatisfaction, and because there is a power supply to continuously provide charge, therefore, the box must be full whenever it is, therefore, there will be part of the charge flowing out or into the capacitor, thus playing a role in accommodating the capacitor. That's why the capacitors are AC.

In fact, it is easy to understand that the box is clearly explained as a box containing water, the box must be full, and the DC cannot cause the volume of the box to change, so there is no water flowing in and out, and there is no current; The volume of the box changes due to the communication, and there will inevitably be water flowing in and out.

The capacitor is actually two very close plates, and the medium in the middle is an insulating material, when the direct current passes through, it is a one-way charging process, and when the charge is saturated, there is no current to pass through. When the alternating current passes through the capacitor, it is the process of forward and reverse charging, and the charge of the capacitor cannot reach saturation, so there is always a current passing through, and the larger the capacity, the greater the current, haha, that's it!

Capacitors cannot pass direct current because in DC circuits, the direction of direct current does not change, and capacitors are equivalent to infinite resistance in direct current, so they cannot pass direct current.

When a capacitor is connected to a power supply, the free charge does not actually pass through the insulating medium between the poles, and the direct current cannot pass through the capacitor. When the voltage rises, the charge gathers on the plates of the capacitor to form a charging current; When the voltage drops, the charge leaves the plates, forming a discharge current.

The main reason is that there is no conductive material between the plates, so DC cannot be passed.

After the pure number of electric charges on the parallel plate capacitor, one plate is positively charged, and the other plate is negatively charged (the charge is on the inner surface of the plate, according to the body surface effect of the charge), the medium between the two allegros can not make the two acacia bending charges transfer and contact each other to complete the charge flow, otherwise, it will not be able to accommodate the charge, that is, it will cause the capacitance to break down, and the capacitance will be useless.

Capacitors, often referred to as capacitors, are represented by the letter C. Definition 1: A capacitor, as the name suggests, is a 'container for electricity' and is a device that holds an electric charge.

Capacitors are one of the electronic components widely used in electronic devices, which are widely used in circuits in terms of DC blocking, coupling, bypass, filtering, tuning loop, energy conversion, control, etc.

1. The resistance of the capacitor to the alternating current is affected by the alternating current frequency, that is, the capacitor of the same capacity presents different capacitive reactance to the alternating current of different frequencies;

2. The polarity of the power supply of alternating current changes periodically with time, and the two plates of the capacitor connected to the AC circuit are suddenly positive on the left and negative on the right, and suddenly the negative lead line on the left plate and positive on the right Huai imitation plate. When the left plate is positive, a large number of electrons with negative charge rush to the right plate through the loop when the left plate is positive by the positive electric field of the left plate, and a large number of electrons from the right plate are attracted by the positive electric field of the right plate through the loop. The positive and negative polarities of the two plates of the capacitor are constantly converted, and electrons flow back and forth through the circuit.

Capacitors have the function of blocking the pre-intersection sensitivity. Here's why:

When a capacitor is turned on for a DC power supply, the charging process only occurs for a short period of time just after it is turned on, forming a charging current in the circuit. After the end of charging, because the voltage at both ends of the capacitor is equal to the power supply voltage, the current in the capacitor circuit is zero, which is equivalent to the capacitor blocking the DC current, and this role of the capacitor is usually referred to as "direct blocking".

When the capacitor is connected to the AC power supply, the maximum value of the alternating current is not allowed to overtake the rated working voltage of the capacitor, because the size and direction of the AC power supply voltage continue to change with time, the capacitor is constantly charged and discharged, so the circuit will repeatedly appear charge and discharge current, which is equivalent to the AC current can pass through the capacitor, usually the role of the capacitor is referred to as "communication".

Because the capacitor has the function of blocking the DC through the cross. The capacitor only occurs during charging for a short period of time just after the DC power is turned on.

A charging current is formed. At the end of charging, the current in the capacitor current is the same as the supply voltage because the voltage across the capacitor is equal to the supply voltage.

is zero, therefore, the function of the capacitor DC current isolation is usually referred to as "direct isolation". When the capacitor is turned on with alternating current.

When the source (the maximum value of the AC power is not allowed to exceed the rated operating voltage of the capacitor), due to the magnitude and square of the AC power supply voltage.

The direction changes over time, and the capacitor is constantly charged and discharged, so the charge and discharge current will repeatedly appear in the circuit, which is quite the same.

As the AC current can pass through the capacitor, this function of the capacitor is usually referred to as "communication".

Capacitive. AC power can pass through the capacitor, but when the capacitor is connected to the AC circuit, due to the continuous charging and discharging of the capacitor, the charge on the capacitor plate has an obstructive effect on the charge of the directional moving field, and this hindering effect is called capacitive reactance in physics, which is represented by the letter XC. Therefore, the capacitance still has a hindrance effect on the alternating current.

The spine-like hindrance effect of capacitance on alternating current is called capacitive reactance. The capacitance is large, and the alternating current is easy to pass through the capacitor, indicating that the capacitance is large and the obstruction effect of the capacitor is small; The frequency of alternating current is high, and the alternating current is easy to pass through the capacitor, indicating that the frequency is high and the impediment effect of the capacitor is small.

xc 1 (2 fc) xc = 1 ( c) = 1 (2 f c) xc ---capacitance reactance; Ohm - angular frequency (angular velocity) f --- frequency, China's national grid power frequency is 50Hz c--- capacitance value Farad knows the frequency of alternating current f and capacitance c, you can use the above formula to calculate the capacitance and anti-slag section.

The mystery of capacitance on AC resistance DC, the microscopic explanation of capacitor on AC resistance DC.

Continuous charging and discharging is equivalent to an electric current passing through, and AC does not mean that the current passes through the plates of the capacitor.

As you said, the capacitor is constantly charged and discharged, because the alternating current changes 50 times in one second, then the capacitor will have 50 such changes, and the direct current will be charged and discharged once, it is this continuous charging and discharging process that we think that the current flows through the capacitor, in order to facilitate the analysis of the circuit, it is believed that the AC signal can pass through the capacitor, and the DC can not. This is the essence of AC isolation DC, if we always think about the capacitor charging and discharging in the work, then in the analysis of the circuit diagram is to encounter difficulties, will enter a dead end, so we simplify its characteristics into a sentence. I don't know if it's clear, hehe.