Where does the energy of the electric field of the capacitor

Granted to themselves, the two electric charges of the same name do not want to have anything in common with each other. They fly away as fast as they can. Thus, if the particles are forced to move towards each other (and this happens, for example, in the accumulation of a charge), they resist this in every possible way, and to increase the concentration density of charges in the conductor, a certain energy must be expended.

In the static state this energy is not used and irretrievably lost. It is stored in the form of an electric field - a kind of tension in the space between the charged particles - until the charge concentration decreases and they again gain the ability to move freely.

In this case, the charges use the stored energy of the electric field to acquire acceleration in its path.

The capacitor is a component of an electrical circuit specially designed to store an electric field.

The energy of the electric field of the capacitor is the basis for its use in numerous electrical and electronic devices.

Simple logic suggests that a capacitor charged to voltage V will require QV joules of energy to reach a new state, and this quantity is just the energy of the electric field of the capacitor, stored in it and ready for use.

Unfortunately, common sense here misfires. If you feel good after drinking a mug of beer, this does not mean that you will feel exactly twice as good after taking the second.

In fact, as the charges approach, they resist it more and more violently. Obviously, here we are dealing with a nonlinear process.

Let us see how the energy of the electric field of a capacitor is determined on the basis of a simple experiment.

It is known that the current is defined as the speed with which the charge moves. Therefore, if a capacitor is connected to a stabilized current source, the charge Q will accumulate on the plates at a constant rate.

Suppose we take an uncharged capacitor and connect it to a power supply that provides a constant charging current I.

The voltage on the capacitor starts from zero and increases linearly until the capacitor is fully charged. After that, it stops. We call this value the maximum voltage V.

The average voltage on the capacitor in the process of charge is (V / 2), and the average power, respectively, is I (V / 2). The capacitor was charged in a time T seconds, so that the energy of the electric field of the capacitor, stored in the process of charging, is equal to TI (V / 2).

W = 1 / 2QV = 1 / 2CV

Despite the existence of a huge number of standard sizes, the construction of a condenser does not differ in a special variety.

Most of them consist of two parallel plates separated by a dielectric. Sometimes, to save space, this sandwich is rolled into a tube like a roll. And in some cases they have several layers, in a certain way connected with each other.

Calculating the capacitance of a capacitor consisting of two metal plates, with known physical dimensions, usually does not present a problem, just as the calculation of the resultant capacitance in the series or parallel connection of capacitors.