The role and principle of inductance
The role of inductance:
Electricity generates magnetism, magnetism generates electricity, the two complement each other and are always displayed together. Inductance When a wire has a constant current flowing through it, a constant magnetic field is always excited around the wire. When the wire is bent into a helical coil, applying the law of electromagnetic induction, it can be concluded that a magnetic field occurs in the helical coil. Put this helical coil in a certain current loop, when the direct current in this loop changes (such as from small to large or vice versa), the magnetic field in the inductor should also change, and the changed magnetic field will bring about a changed "new current". ", according to the law of electromagnetic induction, this "new current" must be in the opposite direction to the original direct current, thus forming a certain resistance to the change of direct current in a short time. However, once the change is completed, the current is stabilized, and the magnetic field no longer changes, there will be no more obstacles.
From the above process, the core function of the inductor is to prevent the change of the current. For example, in the process of increasing the current from small to large, the inductor has a "hysteresis" effect, which can resist this change within a certain period of time. From another point of view, because the inductor has the function of storing a certain amount of energy, it can try to maintain the original state when the change comes, but it should be noted that when the energy is exhausted, it can only follow the current.
The "pass-through-resistance-pass" characteristic of inductors allows them to play a huge role in circuits. In the board, the inductor is mostly used in energy storage, filtering, delay and oscillation, etc., and is an important component to ensure the stable and safe operation of the board.
The principle of inductance:
Inductance is the ratio of the magnetic flux of the wire to the current that produces this magnetic flux when an alternating current is passed through the wire, which generates an alternating magnetic flux around the interior of the wire.
When a DC current is passed through the inductor, there are only fixed magnetic lines of force around it, which do not change with time; however, when an AC current is passed through the coil, there will be magnetic lines of force around it that change with time. According to Faraday's Law of Electromagnetic Induction---Magnetic Electricity Analysis, the changing magnetic lines of force will generate an induced potential at both ends of the coil, which is equivalent to a "new power supply". When a closed loop is formed, this induced potential will generate an induced current. It is known from Lenz's law that the total amount of magnetic lines of force generated by the induced current should try to prevent the changes of the magnetic lines of force. The change of the magnetic line of force comes from the change of the external alternating power supply, so from the objective effect, the inductance coil has the characteristic of preventing the current change in the alternating current circuit. The inductance coil has characteristics similar to the inertia in mechanics, and is named "self-induction" in electricity. Usually, sparks will occur at the moment when the knife switch is opened or the knife switch is turned on. caused by high induced potential.
In short, when the inductive coil is connected to the AC power supply, the magnetic field lines inside the coil will change all the time with the alternating current, causing the coil to generate electromagnetic induction. This electromotive force generated by the change of the current in the coil itself
, called "self-induced electromotive force".
It can be seen that the inductance is only a parameter related to the number of turns, size, shape and medium of the coil. It is a measure of the inertia of the inductive coil and has nothing to do with the applied current.