We all have to deal with the concept of "electrical voltage" almost every day, because the scope of its use is not limited to electrical appliances alone. These are lightning discharges during rain, and sparks on a plastic comb and clothes made of synthetic fabrics, etc.
Dry academic language gives the following definition of this phenomenon: electrical voltage is a physical quantity that indicates the amount of work performed by a charge of 1 C (Coulomb). The pendant, in turn, indicates the amount of charge passed through the conductive material in 1 second at a current of 1 A.
Another definition is also acceptable, according to which the electric voltage is the ratio of the work performed by the electric field to move the test (test) charge between two points, to the numerical value of this charge. It is generally believed that charge transfer does not affect the potential difference (does not change the voltage), and the trajectory can be ignored. In the form of a formula, this definition is written as follows:
U = A / q,
where U is voltage, A is work, q is charge.
In order to remember what the voltage is measured in, there is no need to memorize, because the prompt is always at hand, since the voltage value and its dimension are indicated on all current sources: just look at any battery. The unit is Volt (V, V).
The concepts of "electrical voltage" for DC and AC circuits are different. In alternating current, characterized by the periodic passage of a sinusoid through the zero mark, the actual value is used not for instantaneous, but for calculations. This is possible due to the fact that its operation with an active linear load numerically corresponds to a constant voltage.
The one who happened to encounter three-phase electric motors, probably drew attention to a strange entry in the passport characteristics. There, through the fraction sign, two voltages are indicated, for example, 220/380 V. There is no typo, indeed, the equipment is capable of operating at two different effective values. Where does the 220 V network come from? It turns out that the voltage can be either phase or linear, depending on the measurement method. Phase is determined by measuring the value between each phase and the neutral wire, and linear - between the phase conductors. By connecting the load circuit into a triangle, it is possible to obtain the equality of the linear and phase voltages, and for the "star" circuit the phase is 1.73 times less than the linear one.
To measure the voltage, a special device is used - a voltmeter. Its main feature is the need to connect pick-up probes parallel to the load. High internal resistance does not introduce shunt distortion. That is why, for example, in domestic use, a direct connection to the outlet is possible (unlike an ammeter that is included in an open circuit).
But let’s leave the three-story formulas for academics and understand what “electric voltage” is, in simple human language. So, this is the difference of charges (potentials) between two arbitrary points of a conductor or an electric field. The source that causes the movement of electrons along the conductor (generator, battery) creates an excess of it at one end, and a disadvantage at the other. Accordingly, the value of the charges is also different. It is enough to connect these points with any conductive medium, and an electric current will arise - the movement of charged particles, which tends to level this difference. In other words, the nature of the current implies the tendency of atoms to a stable state, disturbed by the magnetic fields of the generator. Voltage can exist without current, if the resistance between the points is large. This explains the fact that familiar batteries do not “shock”.