The inductance is the ratio of the magnetic flux of the wire to the current in which the flux is generated when an alternating current is passed through the wire to produce alternating magnetic flux in and around the wire.
When a direct current is passed through the inductor, only a fixed magnetic line of force is present around it, which does not change with time; however, when an alternating current is passed through the coil, magnetic lines of force appearing around it will appear around the time. According to Faraday's law of electromagnetic induction, magnetoelectricity, the varying magnetic lines of force produce an induced potential across the coil, which is equivalent to a "new power supply." When a closed loop is formed, this induced potential generates an induced current. It is known by Lenz's law that the total amount of magnetic lines generated by the induced current is intended to prevent the change of the original magnetic lines. Since the original magnetic field line changes from the change of the external alternating current power supply, the objective coil has the characteristic of preventing the current change in the alternating current circuit from the objective effect. Inductor coils have similar characteristics to the inertia in mechanics. They are electrically named "self-sensing". Usually, when the knife switch is turned on or the knife switch is turned on, sparks will occur. This is the phenomenon of self-inductance. Highly induced by the induced potential.
In short, when the inductor coil is connected to the AC power source, the magnetic lines of force inside the coil will change with the alternating current, causing the coil to continuously generate electromagnetic induction. This electromotive force generated by the change of the current of the coil itself is called "self-induced electromotive force".
It can be seen that the inductance is only a parameter related to the number of turns of the coil, the size and shape, and the medium. It is a measure of the inertia of the inductor and is independent of the applied current.