Inductor- Definition, Function, Types, and Applications

An inductor is a passive electrical component that stores magnetic energy when an electric current flows through it. Inductors are used in electronic circuits for filtering, energy storage, and signal processing.

The inductors are coil-like structures made of insulated wire wound around a magnetic core. When the current flows through, the inductor opposes it by inducing back emf, and this opposition offered to the flow of current is called the inductance. The inductance of a conductor depends on turns in the coil, the size of the core, and the type of material. The inductance of the inductor is measured in Henry.

I will explain inductors in this article, covering their definition, function, types, symbols, and applications. To start, let’s define what an inductor is.

What is an Inductor?

Inductors are passive devices that store electrical energy as magnetic energy. An inductor opposes the change of current that flows through it and induces a voltage across it. Thus, it either gains or loses charge to balance the current flow. The other names of the inductor are choke, reactor, or simply coil.

Inductance of Inductor

Inductance is the property of an inductor that opposes a change in the current that passes through it. The inductors induce a voltage across them when they see the change in the current. The ratio of the induced voltage to the current rate of change is known as inductance. The SI unit of inductance is the Henry (H), denoted by the symbol L.

The inductance depends on the shape of the coil, the number of turns in the coils, layers in the wire, Spacing between the turns, permeability of the magnetic core, and size of the core.

Symbols for an inductor

Symbols are given below:


Construction of an Inductor

Inductors have a magnetic iron or ferrite core surrounded by a coil of insulated copper wire. The ferromagnetic core has high permeability, and it is possible to get a large inductance.

Low-frequency inductors are typically constructed with laminated electrical steel to prevent eddy currents. Soft ferrite cores are used above audio frequencies.


Hence, an inductor consists of two main components: the coil, which is made of copper wire, and the core, which can be made of materials such as iron or steel.

Functions of Inductors

Inductors are used primarily for two functions:

  1. To store energy
  2. To Control Signal

Storing Energy

Inductors store energy in the form of magnetic fields. The energy stored in an inductor depends on the amount of current flowing through it and its inductance. The energy stored in inductors can be expressed by the following mathematical formula.

formula for energy stored in inductor

Controlling Signals

The inductor has low reactance for low frequency and high reactance for higher frequency. This property makes them suitable to pass DC current and block AC current.

How does an Inductor work?

When an electric current flows through an inductor, it generates a magnetic field around it. The strength of the magnetic field is directly proportional to the magnitude of the current. Therefore, the magnetic field increases with an increase in current. The generated magnetic field creates flux that links to the inductor coil. The magnetic flux is the measure of the magnetic field that passes through a specific area.

The flux that links to an inductor induces EMF, which opposes the change in the current flowing through the inductor. The rate of change of flux increases with the rate of change of current, resulting in a higher EMF. When there is no change in the current, the current flows normally through the inductor. You can see that DC has a constant magnitude, and it can flow through the inductor without opposition.

Types of Inductors

We can classify inductors on the basis of-

  1. Core Material
  2. Inductance Value

Inductors according to Core Material

Inductors are categorized according to the core material they are constructed from.

  1. Iron Core Inductors
  2. Air Core Inductors
  3. Iron Powder Inductors
  4. Ferrite Core Inductors which is divided into:
    • Soft Ferrite
    • Hard Ferrite

Iron Core Inductors

The iron core inductors are made of an iron core.


The iron has high permeability. Therefore, iron core inductors have high inductance, and they are suitable for high-power applications but not for high-frequency ones. These inductors are generally used in audio equipment.

Air Core Inductors

The air core inductors are used for those applications where low inductance is required. These inductors do not have a magnetic core.


The permeability of the air is low, and to get the same value of inductance as that of an iron core, we need more turns. The quality factor of the air core inductor is high because it does not have an iron core.

Iron Powder Inductors

The core of these inductors is made up of iron oxide. The iron oxide core is made from a very fine insulating particle of pure iron powder. The core contains an air gap that allows high magnetic flux storage. The permeability of the core is below 100, and they are mainly used in switching applications.

Ferrite Core Inductors

In this type of inductor, the core is made up of ferrite materials XFe2O4 ( where X represents transition material).


Ferrites can be classified into two main types: soft ferrites and hard ferrites.

Soft Ferrites

These materials can reverse polarity internally without external energy.

Hard Ferrites

These magnets have a permanent polarity, meaning they do not change even after removing the magnetic field. These are permanent magnets.

Inductors in Series

The inductors connected in series behave like resistors in series. The inductance increases when the inductors are connected in the series. The total inductance equals the sum of individual inductance connected in the series.

The total inductance of the inductors connected in series is given by,


Inductors in Parallel

When two or more inductors are connected in such a way that one end of each inductor is connected to a common point and the other end of each inductor is connected to another common point, then the inductors are said to be connected in parallel.


The voltage across parallel connected inductors is the same. The current flowing through it depends on the value of the inductance.


Inductive Reactance of Inductor

Inductive reactance is the opposition to a changing current flow, measured in ohms like resistance. The inductive reactance of an inductor depends on the frequency and the inductance. The inductive reactance formula is;

The inductive reactance increases with an increase in frequency. For DC, the inductive reactance is zero.

Applications of Inductors

The following are the applications of inductors.

  1. An inductor and capacitor form a tuning circuit, which can be adjusted using variable components to set the frequency. This circuit is commonly used in radio and TV receivers.
  2. The inductor is used in a low-pass filter. A low pass filter provides low impedance for low-frequency signals.
  3. The motor’s stator and rotor windings are formed using coils with inductor characteristics. The inductor with a magnetic core transforms the electrical energy into magnetic energy.
  4. The inductor generates the voltage in the presence of a magnetic field in generators and thus transforms mechanical energy into electrical energy.
  5. The inductors are used to filter out the undesired signal, such as ripples and electronic noise.
  6. The inductors with ferrite beads are used on the cable to eliminate the radio frequency noise.
  7. The inductors are used to improve the voltage regulation of electrical power supply.
  8. The inductors are used to limit the fault current in an electrical network.
  9. The inductors are used in the reactance earthing scheme.
  10. Inductors are used in the proximity sensor to detect the object.
  11. They are used in the transformer for primary and secondary winding.
  12. The relay and contactor coils are inductors that create a magnetic field to attract the plunger.
  13. They are used as a choke to block AC. The inductor reactance is high for AC and low for DC. Thus, it passes the DC and blocks AC.
  14. Inductors are used to store a small amount of energy in the form of a magnetic field. For storing more energy, a larger inductor with high inductance, which increases its size, is required.


In summary, an inductor is a fundamental circuit component that stores electrical energy in the form of a magnetic field. A basic inductor consists of a conductor wire coiled to a finite length.

In this article, I have explained all the major concepts related to inductors. If you have any queries related to this topic, please let me know in the comment section.

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