A component called an inductor is used when the property of inductance is required in a circuit. The basic form of an inductor is simply a coil of wire. There are different types of inductors available for different types of applications. Factors which affect the inductance of an inductor include:

  • the number of turns of wire — the more turns the higher the inductance
  • the cross-sectional area of the coil of wire — the greater the cross-sectional area the higher the inductance
  • the presence of a magnetic core — when the coil is wound on an iron core the same current sets up a more concentrated magnetic field and the inductance is increased
  • the way the turns are arranged — a short thick coil of wire has a higher inductance than a long thin one.

symbol of InductorAn inductor is a component which offers a  high impedance to a.c. but very low to d.c.

Types of Inductors

The inductors, like resistors and capacitors, can be classified broadly as fixed and variable inductors. The different types of inductors are available for different applications and are explained below:

Filter Chokes

A filter choke is an inductor used in the filter section of d.c. power supply. It blocks the a.c. signal and allows the d.c. signals to pass through it. The two major ratings of a filter choke are the inductance and current rating.

types of inductors

Radio-Frequency Chokes

These are smaller in size as compared to filter chokes. Air-core coils for RF applications have very small values of inductance. For example, an RF coil for the radio broadcast band of 535 to 1605 KHz may have an inductance of 250 μH or 0.25 mH.

air core inductor

Variable Inductors

Variable inductors are used in radio frequencies. The winding is placed over a fiber or ceramics former and to change the inductance, a ferrite core is employed.variable inductors