Electric capacitor: how it works and why is it needed in the AC and DC circuits

In almost all electronic devices, from the simplest to high-tech, such as motherboards of computers, you can find one invariably present element, which is passive component. But unfortunately, few people know how the capacitor is arranged and what it is for, and what types of this storage there are.

Just about complicated

So, this small device for accumulating an electric field or charge looks like an ordinary jar, the one in which tomatoes are marinated or flour is stored. In the same way, it accumulates in itself dry matter or liquid, which will be placed in it. The analogy is simple: electrons run along the circuit, and on their way they meet conductors that lead them to the "jar", where they accumulate, increasing the charge.

In order to find out how many electrons can be collected this way, and at what point the accumulation will stop (the bank will burst), the electrical process is usually compared to a water supply system. If you imagine a pipe in which water flows, pumped there by a pump, then somewhere in the center of the pipeline you need to imagine a soft membrane stretching under the pressure of the liquid. Obviously, it will stretch to a certain limit until it bursts or, if caught very strong, balances the force of the pump.

This example shows how a capacitor works, only the membrane is replaced by an electric field, which increases as the storage device is charged (pump operation), balancing the source voltage nutrition. Obviously, this process is not endless, and there is a limit charge, upon reaching which the "bank" will fail and cease to perform its functions.

Device and principle of operation

A capacitor is a device consisting of two plates (plates) with a void between them. Voltage is supplied to it through wiring connected to the plates. Modern devices, in fact, do not differ much from the models in physics lessons, they also consist of a dielectric and plates. It should be noted that it is the substance or its absence (vacuum) that poorly conducts electricity that changes the characteristics of the storage device.

The essence of the principle of operation of the capacitor is simple: they gave a voltage, and the charge began to accumulate. For example, consider how the drive behaves in two variants of the electrical circuit:

• D.C. If a current is applied to the circuit with a capacitor connected to it, then you can see that the arrow on the ammeter will begin to move, and then quickly return to its original position. This can be explained simply: the device charged quickly, that is, the power source was balanced by the plates of the drive, and the current was gone. Therefore, it is often said that a capacitor does not work under constant current conditions. This statement is incorrect, everything functions, but for a very short time.
• Alternating current - this is when electrons move first in one direction and then in the other direction. If we imagine such a circuit with a storage device connected to it, then positive and negative charges will alternately accumulate on both plates of the capacitor. This indicates that the alternating current flows freely through the device.

Since the capacitor delays the direct current, but passes the alternating current, from here are formed and the scope of its purpose, for example, for devices in which it is necessary to remove the DC component in signal. It is quite obvious that the drive has resistance, but the power is not released on it, so it does not heat up.

Main types

An ordinary user does not always know what kind of capacitor his device is equipped with. But each type has its own disadvantages and advantages, as well as operational features. There are two large groups of these devices for AC and DC electrical circuits. But still, the main classification is by the type of dielectric, which is located between the capacitor wafers. Main types:

• Ceramic. They are small in size, small in leakage current and small in inductance. They work perfectly in high frequency conditions, in pulsating, direct and alternating current circuits. They are presented in a different range of voltages and capacities, depending on what the capacitor is intended for.
• Mica. Currently, they are almost never used and are not produced. In storage rings of this type, mica serves as a dielectric. The operating voltage of such capacitors is in the range of 200-1500 V.
• Paper. Capacitor paper is enclosed in aluminum wafers. Withstand voltage 160-1500 V.
• Polyester. The maximum capacity does not exceed 15 mF, the operating voltage is 50-1500 V.
• Polypropylene. They stand out favorably against the background of other brethren by two advantages. The first is a small capacity tolerance (+/- 1%), the second is up to 3 kV operating voltage.

Electrolytic capacitors should be noted separately. Their main difference from other types is connecting only to a direct or pulsating current circuit. Such drives have polarity - this is a feature of their design, therefore, incorrect connection leads to a swelling or explosion of the device. They have a large capacity, which makes the electrolytic capacitor suitable for use in rectifier circuits.

Applications

We can safely say that capacitors are used in almost all electronic and radio engineering circuits. To have an idea of ​​where and why a capacitor is needed, one should recall its ability keep charge and discharge at the right time, and pass AC and not pass constant. This means that such devices are used in many technical fields, for example:

• telephony;
• in the production of counting and storage devices;
• automation;
• when creating measuring instruments and many others.

Electric storage devices can be found both in televisions and in radar devices, where it is necessary to form a high-power pulse, for which a capacitor serves. It is impossible to come across a power supply without these devices or a surge protector.

It must be said that storage devices are also used in areas not related to electrical engineering, for example, in metal production and coal mining, where capacitor electric locomotives are used.