What is an electric current?
If you carefully analyze lifemodern society in terms of technology, it becomes clear that the usual order of things determines the electric current. The structure of society is largely determined by them. You can abandon natural gas, replacing it with solid and liquid fuels; even gasoline for cars is now quite successfully replaced by analogues based on alcohol; but there is nothing to replace the electric current: it is or is, or it is not.
People who are only in general familiar with theelectrotechnics, they often think that in the given field for a long time all is known and calculated. In fact, this is far from the case. Many of the properties that an electric current possesses are axioms (fundamental laws that do not require proof), although this does not hinder the use of electrical appliances in household and production.
To the question "what is an electric current"literature gives an unambiguous answer - this is the directed motion of charged particles. It is known from the basic course of physics that the atom consists of three components: a neutron, a proton and a negatively charged electron (their number varies). Some electrons, located in remote orbits from the nucleus that attracts them, can leave the structure of the atom and remain in a "conditionally free" state. When they pass through special media, formed by the elements of the circuits, electrons perform the work necessary to man. This may be an increase in the temperature of the helix of the heating device, the generation of a magnetic field in transformers and inductors, vibrational perturbations of magnetic fields,
To create such free particles servesources of electric current. The word "creation" is only partly true, since not all sources directly generate a current. Therefore, there is a division into primary and secondary. The first create a current, while the latter accumulate it and, if necessary, give it back. Current generation is performed at power stations (hydro, heat, nuclear, etc.). The windings of the generating machines rotate in a magnetic field, which "knocks out" the electrons from their orbits. Then the flow of these released particles along the power lines is directed to transforming transformers, in accordance with the law of electromagnetic induction, which reduces or increases the effective value of the voltage. Then the current goes to the consumers, where it does the required work. Electrons do not move "anywhere": they are directed back to the generator connected to a huge mass of the Earth, which can accumulate them (almost like people, they want to rest). In the light of the above, it is necessary to indicate the conditions for the existence of an electric current:
- the presence of a closed loop from the conductingmaterial serving for electrons as a kind of bridge between the source of their origin (knocking out of atoms) and earth (mass). This is why there is no electric current before connecting the consumer device to a household electrical outlet, but only voltage;
- The current source constantly creates their flow inconductor. Otherwise, there will be no movement (current). If the power of the source is insufficient to overcome the resistance of the material, then such a conductor is equated with a dielectric.
For a better understanding of the nature of the electric currentit is often compared with hydraulic systems. The current is the movement of the liquid through the pipes, the voltage is the difference in altitude, etc. Although such a comparison can not explain the magnetic properties, it is quite suitable for a general representation.
An interesting point: it is believed that the direct current is directed from the positive pole (plus) to the negative (negative), although in fact the electrons move in the opposite direction.