Inductive coils block the current. Generally, the self-inductive electromotive force in the inductor line always opposes the changes in the current in the coil. Therefore, the air core inductor coil will hinder the AC current. The unit is ohms. Its relationship with the inductance L and the frequency of the alternating current is XL = 2MFL. Inductors can generally be divided into high-frequency current blocking
LC loop resonance phenomenon, when the circuit inductance and capacitive reactance are reversed at resonance, the total loop current inductance is the smallest and the current is the largest. Therefore, the general LC resonance circuit has the function of selecting the frequency. The AC signal is selected, so the inductive coil cannot be judged to be bad because of its current blocking effect.