Introduction of Inductor Coil

Inductive coils are devices that operate based on the principle of electromagnetic induction. When a current flows through a wire, a certain electromagnetic field is generated around the wire, and the wire itself in this electromagnetic field will induce the wire within this electromagnetic field range. The effect on the wire itself that generates an electromagnetic field is called "self inductance", which means that the changing current generated by the wire itself produces a changing magnetic field, which further affects the current in the wire; the effect on other wires within this electromagnetic field range is called "mutual inductance".

The electrical characteristics of an inductor coil are opposite to those of a capacitor, "passing through low frequencies and blocking high frequencies". High frequency signals encounter significant resistance when passing through an inductor coil, making it difficult to pass through; while low-frequency signals present relatively small resistance when passing through it, meaning that low-frequency signals can easily pass through it. The resistance of an inductor coil to direct current is almost zero.

Resistors, capacitors, and inductors all present a certain resistance to the flow of electrical signals in a circuit, which we call "impedance". The impedance presented by an inductive coil to a current signal utilizes the self inductance of the coil. Inductive coils are sometimes abbreviated as "inductors" or "coils", represented by the letter "L". When winding an inductor coil, we generally refer to the number of turns of the coil as the "number of turns" of the coil.