What is an Inductor ?

Inductors

An Inductor is an Electronic  Component which is used to generate a magnetic field. This magnetic field reacts to oppose any change in current. This reaction of the magnetic field, trying to keep the current flowing at a steady rate, this is called inductance of an inductor, and the force it develops is called an induced emf

Symbol of an Inductor

The symbol of an iron-core and air-core inductor are shown below :

Iron-core inductor Symbol

Air-core Inductor Symbol

The inductance is measured in henrys (H)

All Inductors, like resistors and capacitors, can  be listed under two general categories : fixed and variable. Different types of inductors are used in different types of applications




Types of Inductors

There are three types of inductors:

  1. Filter Chokes
  2. Audio Frequency Chokes
  3. Transformers

1. Filter Chokes

laminated core




Filter Chowk

Filter Chokes : Filter chokes are the inductors used in smoothing the pulsating current produced by rectifying ac into dc. A typical filter choke has many turns of wire wound on an iron core. To avoid power losses, the core is made up of laminated sheets of E- and I- shapes. Many power supplies use filter chokes of 5 to 20 H, capable of carrying current up to 0.3A . 





2. Audio-Frequency chokes

Audio Frequency Chowk

Audio-Frequency Chokes (AFCs) : Audio-Frequency Chokes are used to provide high impedance to audio frequencies (say, 60Hz to 5kHz). Compared to filter chokes, they are smaller and have lower inductance. Chokes having still smaller inductance are used to block radio frequencies. Such chokes are called radio-frequency chokes (RFCs). Variable inductors are used in tuning circuits for radio frequencies. The permeability-tuned variable coil has a ferromagnetic shaft. This shaft can be moved within the coil to vary the inductance.

3. Transformers

Transformers : A transformer is quite similar in appearance to an inductor. It consists basically of two inductors having the same core. One of these inductors, or windings, is called primary and the other one is secondary.

Basic Structure of a transformer

When an alternating current is applied at the primary, an induced voltage appears in the secondary. In a step-up transformers, the number of turns in the secondary is greater than the primary winding therefore, the secondary voltage is more than the primary voltage, and in the step-down transformer the number of turns in primary is greater than the secondary windings therefore, the voltage in primary is greater than the voltage in secondary winding. A transformer of suitable turns-ratio is often used in electronic circuits for impedance matching.