Speaking about what is induction current, one cannot but recall the experiment of the great physicist of his time - Michael Faraday. Indeed, partly thanks to his work, we all can now use such a benefit of civilization as electricity. Then, in the 19th century, the only source of electrical energy was chemical elements (batteries). After the experiments of Faraday , generators became available to the world, which changed the whole future history.
Until 1831, physicists were aware of the existence of electric and magnetic fields. It was believed that the interaction of two or more fixed charges (electrons or ions) creates a certain type of tension - an electric field. But mobile charges are interconnected with magnetic fields. It is obvious that at that time there were all prerequisites for discoveries, and they did not take long to wait.
Electromagnetic induction and induction current was discovered in 1831 almost simultaneously by two practical scientists - Faraday and Henry. Surprisingly, this is found in all areas of electrical engineering (for example, there are still disputes about the "father" of radio communications). Considering that Faraday was the first to publish the results of experiments and his interpretation of them, it is generally accepted that he is the pioneer of the phenomenon called “induction current”.
One of the experiments suggested the existence of a certain force (a wave of electricity, by the definition of a scientist), which created an electric current in the conductor. From two opposite ends of the metal rod, several turns of wire were wound. The terminals on one side were connected to a galvanometer, and the battery voltage was applied to the wire on the other side. At the moment the battery was turned on, the galvanometer detected the short-term appearance of an electric current. The same thing happened when the source was turned off. An assumption was made about the appearance of a certain force, a field that creates a current.
The following experience is better known: voltage was applied to the terminals of a small coil from a battery, and current flowed through its turns. It was introduced into the central gap of a larger coil, to the ends of which a galvanometer was connected. When removing and introducing a smaller coil, the device recorded the appearance of directed motion of charged particles. The phenomenon was called electromagnetic induction, and the movement of particles was called "induction current."
As it turned out, the cause of its appearance is a magnetic (electromagnetic field), the intensity lines of which cross the conductor. The strength of the induction current depends on the frequency of this intersection. Moreover, it is not so important whether the conductor crosses the tension line, whether the field itself rotates or if the magnetic field is changing (so, in the first experiment its intensity changed).
The direction of the induction current in the conductor is also not accidental. As you know, around any conductor through which electric current passes, there is a magnetic field with its own lines of tension. Their orientation depends on the direction of current flow.
Here the conductor is introduced into the magnetic field, in it, in the presence of a closed circuit, the movement of charged particles is induced. Based on the properties of the current, a magnetic field appears around the conductor. Moreover, its tension lines are directed in such a way as to compensate for a possible change in the main field that caused the initial generation of the induction current.
In fact, the secondary field does not "allow" the primary to change. If we recall the atomic structure of material objects, including the metal of the conductor, then the physics of this phenomenon becomes clear: ion nuclei attract lost electrons, trying to restore their original state of rest. With increasing intensity of "knocking out" of electrons , the attractive force tends to "extinguish" the external effect. Accordingly, with a decrease in the main field, the secondary, conditioned motion of particles in the conductor supports it.