Basic knowledge of Inductor Choke Coils Inductance coils are made of wires wound around an insulating tube one by one. The wires are insulated from each other. The insulating tube can be hollow, or it can contain iron cores or magnetic powder cores, referred to as inductors. Expressed by L, the units are Henry (H), Milli Henry (mH), Micro Henry (uH), 1H=10^3mH=10^6uH. A. Classification of inductance Classified according to the form of inductance: fixed inductance, variable inductance. According to the nature of the magnetic conductor: air core coil, ferrite coil, iron core coil, copper core coil. Classified by work nature: antenna coil, oscillating coil, choke coil, trap coil, deflection coil. Classified by winding structure: single-layer coil, multi-layer coil, honeycomb coil. B. the main characteristic parameters of the inductance coil 1. Inductance L The inductance L represents the inherent characteristics of the coil itself and has nothing to do with the magni