Often at school physics lessons, the teacher, explaining the topic of electricity, resorts to comparing the electric current with the flow of water. In many cases, although not always, to simplify the understanding of ongoing processes, such a comparison is quite acceptable. Actually, even the word "current" is used specifically in relation to liquids. And what is capacity? This is one of the characteristics of an object, its ability to hold something. For example, everyone knows that the can has a capacity of 3 liters. Obviously, the amount of accumulated water directly depends on the capacity of the vessel. So, if you take two buckets, for example, 8 and 12 liters, then they are equal in height, and the difference is only in diameter. The concept of "electrical capacitance" in this regard is very similar. For example, one of the parameters that affects capacity is dimensions. Electrical capacitance (EE) is the ability to accumulate and retain a certain amount of electricity. Any conductive material has a certain EE, depending on a number of parameters. The process of charge accumulation is possible in the case when there is no possibility of its overflowing to another object with a larger capacity.
Electric capacitance can be expressed through a formula that takes into account the ability to accumulate a charge (potential - v) and the magnitude of the charge itself (q). It is designated by the letter "c":
c = q / v
Electrical capacitance is measured in farads. However, since this value is quite large, micro- and picofarads are more often used in modern electronic circuits. Large capacities are used only in specific devices and calculations. Accordingly, the prefixes "micro and pico" are equal to 1 * 10 in -6 and -12 degrees. The processes taking place are easily described through the electrical capacity of a solitary conductor.
Imagine a conductor located in a non-conductive current medium in which there are no external fields. We connect it to a current source. Some of the electrons fall into the structure of the material, creating an excess potential, that is, these charges under certain conditions (create a circuit) can do the job. They are distributed over the surface with a certain density, which depends on the spatial configuration of the conductor and its size. Around each point charge there is an electric field that affects all other parts of the conductor. The potential of such a solitary conductor is directly dependent on the charge. The ratio of a given charge (q) to potential (Fi) for the conductor under consideration is unchanged, since it depends only on the dimensions (size, shape) and dielectric constant of the medium. In the example, it is not in vain that a solitary conductor is indicated. If there are other bodies next to it, the electric field of unit charges will induce a potential of opposite sign in the surrounding bodies, affecting the final value (it will be less).
The simplest element using the properties of accumulating electric current is a capacitor. It consists of two conductors separated by a dielectric material. Its peculiarity is that the generated electric field is “connected” between the plates (opposite parts of the conductors) and practically does not affect the surrounding bodies, which means that the potential for external work is not wasted.
There are several ways to increase capacity:
- reduce the gap between the plates. An infinite decrease is impossible, since a breakdown of a non-conductive medium may occur, which will lead to a loss of charge;
- pick up non-conductive material with high breakdown resistance;
- increase the area of the plates. In order to maintain acceptable capacitor dimensions, the spatial arrangement of the plates is often changed. For example, two conductors are twisted into rings separated by an insulator.