Current with the name of the positive and negative, and the inductance coil also has a role in the obstruction. There are two sides to everything. Inductance coil is now we know that it has a choke coil, the stop flow may not sound like a very good word, ah, it is very good, to understand:
Inductor choke function: EMF inductance coil in the coil is always with the current changes in the coil resistance. The inductance coil has negative effects on the AC current, block size inductance XL ohms. It f relationship with inductance L and the frequency of the alternating current as XL = 2 pi FL, inductors can be for high frequency resistance and flow resistance of coil and low frequency current coil.
Tuning and frequency: inductor in parallel with the capacitor formed LC tuning circuit. The circuit at the natural oscillation frequency f0 and non AC signal frequency f equal, loop inductance and capacitance are equal, so electromagnetic energy is in the inductance and capacitance oscillates back and forth, the LC circuit resonance phenomena. The resonant circuit of inductance and capacitance equivalent reverse, the loop current the inductive reactance of the minimum amount of current maximum (F = F0 AC signal), LC resonant circuit with frequency selective role, can be a frequency f of the AC signal is selected. A lot of things and can not be used to measure the good and bad, like this inductance coil, not because it has the role of resistance, it is not good to say the inductance coil.