We all know that in order to turn on the light, you need to press the rotary button of the switch, click it. A click - and the lamp lights up, lighting everything around. Usually, few people think about the processes taking place at these moments. In fact, many researchers have devoted years to figure out what voltage and current are.
From the analogy with liquids, the meaning of the word "current" is known to everyone - it is directed movement, flow. In relation to electricity, it is an ordered movement of negatively and positively charged particles. It is important to consider that we are talking not only about electrons, but also about atoms that have lost them. The charge of the electron is negative, but for ions (the mentioned atoms) it is positive. The following example will help you understand what tension is.
Imagine the simplest circuit: an incandescent lamp, a switch connected to the gap of one of the two wires, and a power source. In order for the lamp to light up, it is necessary, first of all, to understand what voltage is and what is the difference between the natural movement of particles and forced movement.
The metal of the wire consists of atoms in which the natural movement of electrons constantly occurs. However, we are not talking about current in this case, since there is an disordered (chaotic, non-directional) movement of them. Particles are “forced” by the electric field to shift in the right direction. Generators at power plants, chemical elements, etc. can serve as its source. There is a direct correlation between the current strength and the field that causes it: with an increase in the electric field, the current also increases.
In general, the current strength is the number of elementary particles "passing" through the conductor per unit time. The total charge of electrons that have passed is measured in coulomb. Hence, the unit of current strength, ampere, is a charge of 1 pendant, passing through the conductor in 1 second.
However, without understanding what voltage is, it is impossible to determine the numerical dependence of the current on the electric field. In fact, the field is a force that makes each electron (or pendant) move in the right direction. However, since the field value differs at each point of the conductor, it was customary to characterize it by the work of moving the charge, and not by abstract force.
So, the voltage is the potential difference at the opposite ends of the conductor connected to the emf source. Voltage is measured in volts. For this, a special device is used - a voltmeter. It is connected in parallel with the load: for the above example, two voltmeter probes are connected to the corresponding two lamp contacts. This allows you to measure the field strength between these points.
To simplify the understanding, one can imagine the very “behavior” of charged particles in a conductor. An electron, as already indicated, has a negative charge, therefore, it is attracted to particles with the opposite sign of charge. The higher the concentration of ions at any pole, the more free electrons in the conductor (because they are part of the atoms). This difference between the ratio “-” and “+” is voltage.
Field (voltage) is generated at power plants. Based on the law of electromagnetic induction , an electromotive force arises in a conductor crossing the lines of magnetic field strength. It is enough to connect the load and create a circuit, as the voltage appears. In generators, an external force (water, steam, wind) rotates an electromagnet, which induces EMF in its windings. Each winding forms a phase. The most common three-phase voltage. To create it, the generator immediately contains three windings placed in a certain way (120 degrees behind each other).