Inductance within the lead through the exchange of current in the conductors within and around the alternating magnetic flux, current ratio of this flux and magnetic flux produced wire.

Changes in the current generates a magnetic field and magnetic field changes will be induced electromotive force, the parameters of the linear relationship, we called inductance. Ideal inductor does not produce or consume energy, but due to electromagnetic mutual conversion, but has the function of storing and releasing energy. According to Faraday's law, we can observe the following behaviors:

(1) the inductor current can not change instantaneously.

(2) the current phase will lag the voltage by 90 degrees.

(3) If the current is constant, the induced electromotive force is not.

Therefore, the inductor current can be used as a stable component, may be used as phase-matching components, but also as a low-pass component; of course, the use of an inductor, and more variety of changes, such as energy storage, release energy, resonance, bypass ... and many more.