Often at school lessons of physics teacher, explaining the theme of electricity, compared to the uses of electrical current over the flow of water.In many cases, though not always, to facilitate the understanding of the processes that comparison is quite acceptable.In fact, even the word "current" is used in relation to liquids.And what is the capacity?This is one of the characteristics of the object, its ability to contain something.For example, everyone knows that the capacity of the banks is 3 liters.Obviously, the amount of accumulated water is directly dependent on the tonnage of the vessel.Thus, if we take the bucket, for example, 8 and 12 liters, the height they are equal, and the only difference in diameter.The term "electric capacity" in this context is very similar.For example, one of the parameters affecting the capacity - is the size.The capacitance (E.E.) - The ability to accumulate and retain a certain amount of electricity.Any conductive material has a certain EE, depending on a number of parameters.Charge accumulation process is possible in the case where there is no possibility of overflow to another object having a higher capacity.
electric capacity can be expressed by a formula that takes into account the ability to store charge (potential - v) and the amount of the charge (q).Denoted by the letter «c»:
c = q / v
The capacitance is measured in farads.However, as this value is high enough, in modern electronic circuits often used micro- and PF.Large containers are only used in specific devices and calculations.Accordingly, the prefix "micro and pico" equal to 1 × 10 -6, and -12 degrees.Easy to describe the ongoing processes through the electrical capacitance secluded conductor.
imagine the conductor, which is in non-conductive medium in which there are no external fields.Connect it to a power source.Some of the electrons enters the structure of the material, creating excess capacity, that is, the charges under certain conditions (create outline) can do the job.They are distributed over the surface of a certain density which depends on the spatial configuration of the conductor and its dimensions.Around each point charge exists an electric field that affects all other portions of the conductor.The potential of such an isolated conductor is in direct proportion to the charge.The ratio of the charge (q) the potential (Fi) for the considered conductor always, since it depends only on the size (size, shape) and the coefficient of dielectric constant.In the example, it is not for nothing that indicated a solitary conductor.If there is next to him of other bodies, the electric field will induce a single charge in the surrounding bodies of the potential of opposite sign that affects the final value (which is smaller).
simplest element that uses an electric current to accumulate - a capacitor.It consists of two conductors separated by a dielectric material.Its peculiarity is that the electric field is generated by the "link" between the electrodes (opposing portions of the conductors), and virtually no impact on the environment of the body, and thus the potential at the external work is not wasted.
increase capacity in several ways:
- reduce the gap between the plates.Endless decrease is impossible, since it may be the breakdown of a non-conductive medium, resulting in the loss of charge;
- choose a non-conductive material with a high resistance breakdown;
- increase the area of the plates.In order to maintain acceptable dimensions of the capacitor often change the spatial arrangement of the plates.For example, two conductors are wound into rings, separated by an insulator.