The study of electricity as a physical phenomenonbegins with the school bench. Many teachers, in order to simplify the students' understanding of the material presented, resort to comparing the electric current in the conductor with the motion of the liquid through the pipe. And although this comparison is approximate, it is possible to describe schematically all the processes connected with the phenomenon of electricity as a whole and the flow of electric current in the 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 taking place without trying to find them an analogue in the world of mechanical phenomena.
To describe the electrical phenomena that occurin conductors, use a whole set of different values and parameters. Of course, for the practical application of electricity we are interested in the power of the current, but to determine this parameter one has to get acquainted with other basic characteristics of the flow of electricity in the conductor.
Strength is one of the important characteristicsthe action of electric current. In terms of its physical meaning, it shows the amount of electricity (the amount of charge) that passes the electric circuit per unit time. For this purpose, the value of the electric charge passing through the cross section of the conductor per unit time is taken into account. In mathematical form this value looks like a pendant (Cl) divided by a second (s). The current ampere (A) is taken as the unit of current intensity measurement.
The next parameter, which is taken inattention, when calculating the power of the current, is voltage. Given that an electric current is an ordered displacement of particles that have a charge, an electric field is necessary to create this motion. So, to determine the voltage value, calculate the ratio of the work of the current on a particular section of the circuit to the charge flowing through it. For the voltage unit, it was decided to take the volt (B), which is physically equal to the ratio of the unit of work J to the unit of charge Kl.
Using an ammeter connected to the circuitsuccessively, determine the magnitude of the current, and the voltmeter connected in parallel - the voltage. The power of the current is determined analytically, multiplying the force by the voltage. Taking into account the previously accepted physical definitions of the parameters, we obtain the power unit J / s or one watt (W). Practically, we considered an example of calculation in the ideal case, in which the power of a direct current was determined.
It's only often in everyday practice that wewe are dealing with a three-phase current. We determine the power of the three-phase current as the sum of the powers of each individual phase. Taking into account that each of them operates in the alternating current mode, the power factor cos j is added to the power calculation.
Calculating the total current for differentways of connecting the load for a three-phase current (and we know them two - a triangle and a star) we get that after simple mathematical transformations the formula for calculation in both cases took the same form. To the product of the voltage at the linear current and the load factor cos j, a factor equal to the square root of the three (or in the approximate calculus 1.73) is added.
Having studied the concept of "power current", it is worth recallingexistence of its two main species. Transformation into other types of energy is characteristic of active electrical power. It can be light, thermal, mechanical and others. Watts, kilowatts, megawatts are used for the measurement.
When considering reactive electrical energymean the value, which is characterized by electric load, is created by the consumers of the energy of the oscillation of the electromagnetic field. Often this type of energy is characteristic for engines. As a unit of measurement take volt-ampere reactive (VA).
