What are inductors and their functionality?

The inductor is a passive two-terminal component that temporarily stores energy in the form of a magnetic field. This is commonly called a coil. The main property of an inductor is that it resists any change in current.

Inductors are used to reduce or control electrical spikes by temporarily storing energy in an electromagnetic field and then releasing it back into the circuit.

According to Faraday’s law of electromagnetic induction, when the current flowing through the inductor changes, a time-varying magnetic field generates a voltage in the conductor.

According to the lens law, the direction of the induced EMF opposes the change in the current that produced it. Therefore, the induced emf is opposite to the voltage applied across the coil. This is a property of an inductor.

An inductor is a passive component used in most electrical electronic circuits to store energy as magnetic energy when electricity is applied to it. One of the key properties of an inductor is that it resists or resists any change in the amount of current flowing through it. Whenever the current in the inductor changes it either gains charge or loses charge so as to equalize the current passing through it. The inductor is also called a choke, reactor, or just coil.


An inductor blocks any AC component present in the DC signal. The inductor is sometimes wrapped over a core, for example, a ferrite core.

Core wounded with wire inductors

Various Parts of Inductors

Parts of Inductors

An inductor is described by its specific nature of inductance, which is defined as the ratio of voltage to the rate of change of current. Induction is the result of the induced magnetic field on the coil. It is also determined by several factors such as;

  • The size and shape of the coil.
  • The number of turns and layers of wire.
  • The space is given between turns.
  • Permeability of the core material.
  • The Size of the core.

SI Unit and Symbol of Inductor

The SI unit of inductance is Henry (H) and when we measure the magnetic circuit it is equal to Weber/Ampere. It is indicated by the symbol L.

An inductor is completely different from a capacitor. In the case of a capacitor, it stores energy as electrical energy but as mentioned above, an inductor stores energy as magnetic energy. A key feature of an inductor is that it also changes its polarity while discharging. In this way, the polarity during discharging can be made opposite to the polarity during charging.

Symbols for an inductor

Symbols of Inductors

Construction of an Inductor

Looking at the construction of an inductor usually consists of material (widely used insulated copper wire included) wrapped around a core made of plastic material or ferromagnetic material. An advantage of using a ferromagnetic core is that it has high permittivity which helps to amplify the magnetic field as well as keep it confined to the inductor. Ultimately this results in high inductance.

On the other hand, low-frequency inductors are usually built like transformers. They have a core made of electrical steel that is laminated to help prevent eddy currents. ‘Soft’ ferrites are also widely used for cores above audio frequencies.

Inductors come in many sizes and types. In some inductors, there will be an adjustable core that allows the inductance to change. Inductors used in blocking very high frequencies are mostly made by stringing a ferrite bead onto the wire.

Planar inductors are made using planar cores while small value inductors are made on integrated circuits using interconnect-making processes. Typically, an aluminum interconnect is used and fixed in a spiral coil pattern. However, the smaller dimensions have some limitations. They prohibit installation.

There are also shielded inductors that are commonly used in power regulation systems, lighting and other systems that require low-noise operating conditions. These inductors are often partially or completely shielded.

Various Types of Inductors

On the basis of the type of material used inductors can be classified as follows:

  1. Iron Core Inductor.
  2. Air Core Inductor.
  3. Iron Powder Inductor.
  4. Ferrite Core Inductor.

Iron Core Inductor

The core of this type of inductor is made of iron. These inductors are low spec inductors having high power and high inductance value. However, they are limited in high-frequency capability. These inductors are used in audio equipment.

Air Core Inductor

These inductors are used when the amount of inductance required is small. Since there is no core, it has no core loss. But the number of turns of the inductor should be higher for this type as compared to the inductors with the core. This results in a higher quality factor. Generally, ceramic inductors are often referred to as air-core inductors.

Iron Powder Inductor

In this type of inductor, the core is iron oxide. They are made from very fine and insulating particles of pure iron powder. Due to the air gap, high magnetic flux can be stored in it. The core of this type of inductor has very low permeability. They are usually below 100. These are mainly used in switching power supplies.

Ferrite Core Inductor

In this type of inductor, ferrite material is used as the core. The general structure of ferrites is XFe2O4. where X represents the transition material.

Ferrites can be classified into two types:

  • Soft ferrites: A material that has the ability to reverse its polarity without any external energy.
  • Hard ferrites: These are permanent magnets. That is, their polarity will not change even if the magnetic field is removed.

What is Choke?

A choke is a type of inductor primarily used to block high-frequency alternating current (AC) in an electrical circuit. On the other hand, it will allow DC or low-frequency signals to pass through. Since the function of this inductor is to restrict the change in current, it is called a choke. This inductor consists of a coil of insulated wire wound on a magnetic core. The main difference between chokes and other inductors is that in their cases they do not require the high Q factor manufacturing techniques to reduce the resistance in inductors found in tuned circuits.

Functions of an Inductor

Inductors can be used for two primary functions.

  1. To control signals.
  2. To store energy.

Controlling Signals: The coil in an inductor can be used to store energy. The work of the inductor depends on the frequency of the current passing through it. This is why higher frequency signals will be passed less easily and vice versa. This function states that it blocks AC current and passes DC current. Therefore, it can be used to block the AC signal.

Inductors can be used with capacitors to make LC filters.

Storing Energy: The inductor stores the energy in the form of magnetic energy. Coils can store electrical energy in the form of magnetic energy by using the property that an electric current flowing through a coil generates a magnetic field, which in turn generates an electric current. In other words, coils provide a means of storing energy based on inductance.

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