Choke effect

　　 The self-induced electromotive force in the inductance coil always counteracts the current change in the coil. The inductance coil has an obstructive effect on the alternating current, and the size of the obstructive effect is called the inductive reactance xl, and the unit is ohm. Its relationship with inductance l and alternating current frequency f is xl=2πfl, and inductors can be mainly divided into high-frequency choke coils and low-frequency choke coils.

　　Tuning and frequency selection

　　The inductance coil and the capacitor are connected in parallel to form an lc tuning circuit. That is, the natural oscillation frequency f0 of the circuit is equal to the frequency f of the non-AC signal, and the inductance and capacitive reactance of the loop are also equal, so the electromagnetic energy oscillates back and forth between the inductance and the capacitance, which is the resonance phenomenon of the lc loop. At resonance, the inductive reactance and capacitive reactance of the circuit are reversed. The inductive reactance of the total loop current is the smallest and the current is the largest (referring to the AC signal of f="f0"). The lc resonance circuit has the function of selecting the frequency and can An AC signal of frequency f is selected.