What is Inductor?


Inductor- It is a two-terminal passive electronic component. It is used to resist the change in current flow in the circuit. It can store electric energy in the form of magnetic energy temporarily, when electric current is flowing through the inductor's coil. An inductor is also called a choke or just a coil. Normally, inductors are coil-like structures that are found in electronic circuits.


Construction Of an Inductor- Inductors consist mainly two parts for their construction-
A) Iron or ferrite core
B) Copper Coil

A copper wire is turned into a coil. Coil is wrapped around the core, and the coil is insulated to avoid short circuit. Coil can be in different sizes and shapes. Iron or ferrite core material for the core is chosen intentionally to increase permeability. If the permeability of the material used in core is high, it increases the magnetic field.



How does an Inductor work?

Let us learn about the working of the inductor with the example of the simple circuit as shown below.


In the above image there is
Inductor
Battery
Bulb
Switch

A bulb is basically a resistance because the filament inside it has a higher resistance value. Resistance causes the heat in bulb filament and bulb eventually start to glow. The inductor has a wire which is turned into the shape of coil and wrapped around a core. As shown in the above image switch is turned off and circuit is open, there is no current flowing through the circuit. Bulb is not glowing. But what would happen when the switch is turned on. One might think bulb will glow very dimly because it has high resistance as the circuit gets closed. And current will flow through the coil because coil is just a wire. But this is not the case.


When the switch is turned on, the bulb does glow bright instantly and after gets dimmer and dimmer. But why does that circuit act in that way. This is because in the above circuit when current enters the coil, coil starts to build magnetic field from the current and the inductor has a large coil. Until the coil is creating magnetic field current will not flow through the inductor or very small amount of current flow through the inductor. Then current will flow through the bulb, and it glows brightly. But when the magnetic field is created to its maximum then current will start to flow through the coil wire. And the bulb will slowly get dimmer and dimmer until it gets fully turned off. When the circuit gets open again the bulb will not turn off instantly, it slowly gets dimmer and dimmer and then gets fully turned off.



Because the magnetic field in the inductor coil is collapsing, and magnetic field energy is converting into electric energy. This causes current to keep flowing in the bulb and bulb keeps glowing after circuit is open. Bulb stops glowing when the current stops flowing and the current stops flowing right after when magnetic field is collapsed totally.


This is the reason behind the inductor why it resists any change in the amount of current flowing through it.



Inductance-It is defined as the property of a conducting wire which is formed into a coil that opposes any change in current flowing through it.

The symbol for inductance is L, in honor of the physicist Heinrich Lenz.

Symbol of Inductor-



SI Unit of Inductance- The SI unit of inductance is Henry (H).



Factors Affecting Inductance-


The inductance of an inductor depends upon four factors:

Material of the core- If the material of core inside of the coil has a greater amount of permeability it will cause a greater amount of inductance. Because if the magnetic permeability of core is greater it leads to greater magnetic field around the coil. Ferrite is a commonly used material for inductor cores. Because ferrite has high magnetic permeability.

Area of the coil- If the coil is covering more area round the core, then it will result in less opposition to the formation of the magnetic flux.

Length of the coil- Inductance is inversely proportional to the length of the coil. The greater the length of coil, the less the inductance and vice-versa.

Number of turns of coil- Numbers of turns in coil is directly proportional to the inductance. If a coil has more turns of wire, then it will lead to more inductance, if the coil has less numbers of turns then the coil will have less inductance.

Inductors in Series-

Inductors are said to be connected in series when –ve of the first inductor is connected to the +ve of the second inductor and the –ve of second inductor is connected to the +ve terminal of the third inductor and soon on.



When inductors are connected in series the total or equivalent inductance is the sum of individual inductance of each inductor.

Leq = L1 + L2 + L3 + ... + Ln

In a series circuit, the current across all inductors remains the same. The voltage across each inductor in series is different. And the total voltage of the circuit is the sum of the voltages across all the inductors.

Inductors in Parallel-

Inductors are said to be connected in parallel when –ve terminal of first inductor is connected to –ve of the second inductor and –ve of the second inductor is connected to the –ve terminal of the third inductor and so on. And the same connections are made with all positive terminals.





The equivalent inductance of inductors connected in parallel is always less than the smallest individual inductance present in the circuit.

1/Leq = 1/L1 + 1/L2 +1/L3 + ... + 1/Ln

In parallel circuit, inductors do not have the same current across each of them. The sum of current across each inductor adds up to the total current. But inductors in a parallel configuration have the same potential difference (voltage) across each of them.

Applications Of Inductor-

Main Applications are as following-

In Induction Motors- Induction motors are used to convert electrical energy into mechanical energy. We saw many electrical appliances around us in daily life like ceiling fans, simple electric motors to pump water, all these motors are induction motors.

Inductor used in Transformers- Inductors can be used to form a transformer.

Use as Filter- Most of the electronics circuits use D.C. power supply. For that the A.C. is converted into D.C. To Convert alternating current into direct current rectifier is used. But rectifier does not give the pure D.C., it generates pulsating D.C. To filter these impurities(pulses) in the D.C. inductor is placed in series between the output of the rectifier and the load. Due to the nature of the inductor to block A.C. flowing through it and give a clear passage to D.C., pulsating direct current is converted into pure direct current.

Use to Store Energy- Inductors can be used to store energy but only for a small period of time. It is more like a temporary energy storage device.



Types of inductors

1. Iron Core Inductor
2. Air Core Inductor
3. Ferrite Core Inductor
4. Variable Inductor
5. Bobbin Based Inductors
6. Coupled Inductor
7. Iron Powder Inductor

1. Iron Core Inductors- This type of inductor is made from iron core inside of coil. It is a fixed value inductor. Iron core inside the coil of inductor increases the inductance of inductor. It is high power inductor. It is limited in high-frequency capacity and causes energy losses at high frequencies.

2. Air Core Inductor- It is wire basically and turned into a coil shape structure. It is hollow and does not contain any core and uses air inside of coil.


Copper coil generates a magnetic field when an electric current passes through it. And electrical energy is converted into magnetic field energy. Coil wire is normally made of copper. And wire is insulated if it is not insulated the current will take a shortcut and not flow multiple times around the core. Air coil inductors are used in low inductance and high frequency applications.

3. Ferrite Core Inductor- As the name suggests, an inductor is made of ferrite material core. An insulated wire is winded around a ferrite core. Iron oxide, zinc, manganese, and nickel are mostly used to make ferrite core.


Ferrite core increases the magnetic field formation and the value of inductance.

Ferrite core inductors are divided into two categories

A.) Soft Ferrite- Polarity of soft ferrite inductors can be changed.
B.) Hard Ferrite- Polarity of hard ferrite inductors cannot be changed.

4. Variable Inductor- A variable inductor allows to change its inductance value by changing the ferrite core position.


A variable inductor is commonly used in radio frequency circuits and wireless communication systems to tune or adjust the values of inductance according to different frequencies and signals.

5. Bobbin Based Inductor- This inductor is made by winding a wire around a cylindrical bobbin. The core material is made of ferrite. Bobbin inductor can operate on 60Hz frequency to MHZ range. This type of inductor is used in switch mode power supplies (SMPSs), filter circuits and power conservation circuits.

6. Coupled Inductor- A coupled inductor is made by winding two coils in a single core. Coupled inductor working is based on mutual inductance. Mutual inductance refers to the phenomena of two closely placed coils when magnetic field of one coil induces voltage in second coil. In coupled inductor energy is transferred from one winding to another. The numbers of turns in both coils can be equal or not equal. The coupled inductor and transformer are not the same, both are two different things. The key difference between transformer and coupled inductor is that transformer does not st

7. Iron Powder Inductor- Compressed pure iron powder of fine, insulated particles is used to make the core of iron powder inductor. Air-gap in it allows it to store high magnetic flux. Iron powder core inductors exhibit very low eddy current losses as well as very low hysteresis losses. The permeability of the core of this type of inductor is very little below 100 henrys. This type of inductor is used in low frequency DC output devices, switching power supplies, filters, and radio frequency circuits.