The study of electricity as a physical phenomenon begins with the school bench. Many teachers, in order to simplify the students' understanding of the stated material, resort to comparing the electric current in the conductor with the movement of the liquid through the pipe. And although this comparison is approximate, it is still possible to describe schematically the processes associated with the phenomenon of electricity in general and the flow of electric current in a conductor in particular. But, as practice shows, it is much easier to master all the subtleties of this vast section of physics, if we immediately consider the actual processes without trying to find them an analog in the world of mechanical phenomena.
To describe the electrical phenomena occurring in conductors, use a whole set of different quantities and parameters. Of course, for the practical application of electricity, we are interested in current power, but to determine this parameter we will have to get acquainted with other basic characteristics of the flow of electricity in a conductor.
Strength is one of the important characteristics of an electric current. In its physical sense, it shows the amount of electricity (the amount of charge) that an electric circuit passes per unit of time. For this, the value of the electric charge passed through the cross section of the conductor per unit time is taken into account. In mathematical form, this value looks like a pendant (C) divided by a second (s). Amperes (A) are taken as a unit of measurement of current strength .
The next parameter that is taken into account when calculating the current power is voltage. Given that electric current is an ordered movement of particles having a charge, the presence of an electric field is necessary to create this movement. So, to determine the magnitude of the voltage, the ratio of the current in a particular section of the circuit to the charge flowing through it is calculated. For a unit of voltage, it was decided to take a volt (V), which is physically equal to the ratio of a unit of work J to a unit of charge Cl.
Using an ammeter connected to the circuit in series, we determine the magnitude of the current, and a voltmeter connected in parallel - the voltage. The current power is determined analytically, multiplying the force by the voltage. Given the previously accepted physical definitions of the parameters, we get a unit of power J / s or one watt (W). In practice, we considered an example of calculation in the ideal case, in which we determined the DC power.
That's just often in everyday practice we are dealing with a three-phase current. We determine the power of a three-phase current as the sum of the capacities of each individual phase. Considering that each of them operates in AC mode, the load power factor cos j is added as a factor to the calculation of power.
Having calculated the total current power for different ways of connecting the load for a three-phase current (and we know two of them - a triangle and a star), we find that after simple mathematical transformations, the calculation formula in both cases took the same form. A multiplier equal to the square root of three (or approximately 1.73) is added to the product of the voltage by the linear current and the load power factor cos j.
Having studied the concept of "current power" it is worth recalling the existence of two of its main types. Active electric power is characterized by conversion to other types of energy. It can be light, thermal, mechanical and others. For measurement, watts, kilowatts, megawatts are used.
When considering reactive electric energy, they mean a value that is characterized by an electric load, the oscillations of the electromagnetic field created by energy consumers. Often this type of energy is characteristic of engines. As a unit of measurement, take a volt - ampere reactive (VAR).