Resistance of capacitor

Condenser is one of the most common elements of electronic circuits. Types of capacitors, some of their parameters, such as the resistance of a capacitor, are discussed in this article.

It can be said that two metal electrodes separated by a layer of air are a condenser. Each of the plates has its own terminal and can be connected to an electrical circuit. Such a device has certain characteristics, and one of them is the resistance of the capacitor.

The capacitor or, as it is also called, capacitance, is a very curious device. Suffice it to say that it does not transmit direct current. If one looks at the passage of a direct current from this point of view, then the resistance of the capacitor is very large, almost infinite for a constant current.

At the same time, at the first moment, when the capacitor is connected to the DC circuit, its charge occurs. Inside it there are complex processes. After the capacitor is charged, the current flow practically ceases. But there is one nuance, due to the quality of the dielectric. No matter how good a dielectric is, it still has a tiny current through it. It is called a leakage current.

It is the leakage current that serves as an indicator of the quality of the dielectric used in the manufacture of capacitors. The better the dielectric, the less leakage current. Here one can consider one circumstance: there is a voltage value up to which the capacitance is charged, is the leakage current that flows through this charged element. Hence, according to Ohm's law, it is possible to calculate the resistance of the capacitor. It will be large, the leakage currents of modern tanks make up fractions of a microampere.

The picture looks a little different when the capacitor is under the influence of an alternating current. The current flows freely through the tank. This is explained by the fact that the process of discharge-charging of the capacitor is constantly occurring. And any process of current flow is associated with its losses due to the presence of resistance, in this case, in addition to the active resistance of the wires, there is a capacitive resistance of the capacitor, caused precisely by the processes of its charging and discharging.

The electrical properties of the finished product depend on many factors. These include shape, geometric dimensions, type of dielectric. There are different types of capacitors, as a dielectric they use vacuum, air, plastic, mica, paper, glass, ceramics, aluminum-electrolyte, tantalum electrolyte.

The last two types of capacitors are called electrolytic, they usually have an increased capacity. Other capacitors are called dielectric-paper, ceramic, glass. Each of them has its own peculiarities, its behavior under different electric current parameters, its characteristics and application.

Thus, ceramic capacitors are most often used in circuits for filtering high-frequency interference, electrolytic capacitors are used to filter interference at low frequencies. And together, with parallel connection of ceramic and electrolytic capacitors, the most common filter is used, which is used in almost all circuits. In all cases, the capacitance is a fixed value, such as 0.15 μF.

It should be noted the presence of capacitors of variable capacity, in them the capacity varies depending on the position of the control knob. This is achieved by changing the mutual overlap of the capacitor plates. As a particular case of capacitors of variable capacity, there are so-called tuning capacitors. In them, the capacity can also vary - but within limited limits and only at the stage of adjusting the equipment.

The nomenclature of the capacitors used is simply enormous - both in terms of dielectric type, and in terms of design.