An inductor is a coil of wire, wound over a former made of paper or plastic. It may have a central core made of iron, iron-dust or ferrite. The core increases the reactance of the coil and as a result its inductance. Inductors are used at both low as well as high frequencies. Some high frequency inductors do not need any core at all.
RF circuits commonly use inductors, for controlling the frequency and the amplitude of the wireless waves. Inductance of an inductor is measured in terms of Henry. Inductors may be made of solid, hollow or multi-strand copper wires depending on their usage.