Inductor uses the principles of electromagnetic induction. Here, we are going to discuss the working principles and applications of an inductor. When a changing current which is usually an alternating current (A.C) is fed into an inductor a voltage is induced into the inductor in the direction of which always opposes the change in that current. This current is always reserved in the coil of the Inductor. So, if an Inductor is used in a D.C. circuit, an inductor will oppose (not prevent) any rise or fall in current, although the magnitude of that current will be determined by the resistance of that inductor, not by its inductance. In an A.C. circuit, because the current is continuously changing both in magnitude and in direction, it acts to continuously oppose the current due to its inductive reactance.

 Inductive reactance is proportional to the inductance of the inductor and the frequency of the supply. The vector sum of the inductive reactance of the inductor and the resistance of the inductor is termed the impedance of the inductor. Inductive reactance, resistance, and impedance are each measured in ohms.


Inductors have various uses in electrical transmissions based on their requirements.

Inductors as transformers 

When using inductors as a transformer, the configuration is in such a way that it has a shared magnetic path. Usually, a transformer is a very important component of electrical grids in many power supplies mainly used to increase or decrease voltages to a required level. Whenever there is a changing current in a coil, magnetic fields are created. This is the same principles in transformers. The rule is that, the faster the current changes (increase in frequency) the more effective a transformer will operate. However, as the frequency of the input signal increases, the impedance which is one of the characteristic features of the inductor begins to limit the effectiveness of a transformer.

In a more practical way, inductance based transformers are limited to the 10s of kHz, which much lower. This is one of the advantages of the Inductor type transform over the usual transformers. The higher operating frequencies do not really affect the workability of the transformer. This configuration also helps manufacturers to achieve a smaller and lighter weight transformer that can still be used to drive the same load effectively as a bigger coil type transformer.

Inductors as filters

As the name of the filter circuit suggests, the Inductor is connected in series between a rectifier circuit and the load. The working principle is that the inductor carries the property of opposing the change in current that flows through it. By this I mean, the inductor offers high impedance to the ripples but no impedance to the desired DC components. By so doing, the ripple components will be eliminated. As the rectifier output current increases above a certain value, energy is eventually stored in it in the form of a magnetic field and this energy is used up when the output current falls below the average value. Thus all the sudden changes in current that occurs in the circuit will be smoothened by placing the inductor in series between the rectifier and the load.

In such a circuit, for zero frequency DC voltage, the choke resistance Ri in series with the load resistance RL forms a voltage divider circuit, and thus the DC voltage across the load is

VDC = RL/(Ri + RL)


VDC is the output from a full-wave rectifier. In this case, the value of Ri is negligibly small when compared to RL.

Inductors as chokes

We take RF chokes as applications of inductors. The chokes are designed as fixed inductors with the purpose of suppressing high-frequency alternating current (AC) signals, including signals from radio frequency (RF) devices and allowing the passage of low-frequency and DC signals. Speaking emphatically, ideally, an RF choke is an inductor that rejects all frequencies and passes only DC. Before we can achieve this, the choke (or the inductor) must have very high impedance over the range of frequencies it is designed to suppress, according to the formula.

XL = 6.283*f*L

Relationship between Impedance, Frequency and Inductance of a choke(Inductor)

Where; XL is the Impedance, f is the frequency of the signal and L is the inductance.

We observe that the higher the frequency, the higher the impedance, so a signal with higher frequency will encounter an equivalent resistance (impedance) that will block its passage through the choke. Low-frequency and DC signals will pass through with little power loss.

Inductors as ferrite beds

Recent chargers come with ferrite beds especially computer charging cables even cell phones cables. Inductors are useful in making these ferrite beds which help in reducing the frequency of radio interface which the cable creates while charging the computer system of a cell phone.


Inductor as relays

A Relay is an electromechanical switch. By this, I mean a switch which works under the electromagnetic field created by an inductor. Remember, there is an electromagnetic field created in the coils of an inductor. This electromagnetic field is used to create contact between two electrical connecting points. When AC current flows through the relay circuit, the electromagnetic field will be immediately created which will force the contact of these two points.

Inductors in tuning circuits

A tuning circuit makes use of the Inductor with the capacitor in selecting the desired frequency. The inductor actually helps many electronic devices such as radio and television to modify the frequency and help choose within multiple channels of frequency.

The formula of a parallel tuning circuit – WORKING PRINCIPLES AND APPLICATIONS OF INDUCTOR

Inductors as sensors

Carry out a lab experiment as follows:

  • Take a coil of wire let’s say 6 feet (2 meters) in diameter, containing five or six loops of wire.
  • Cut some grooves in an open space that signifies the road; place the coil in the grooves.
  • Attach an inductance meter to the coil and see what the inductance of the coil is.
  • Bring a metallic object between the two coils in the groove; observe the reading of the inductance meter.
  • Bring more metallic objects between the two coils in the groove; observe the reading of the inductance meter.

The inductance will be much larger because more metallic objects are positioned in the loop’s magnetic field.

Likewise, the inductive proximity sensors used in controlling traffic on the roads. Using, the car parked over the coil is acting like the core of the inductor, and its presence changes the inductance of the coil. The sensor constantly tests the inductance of the loop in the road, and when the inductance rises it knows there is a vehicle waiting.

Inductors as energy storage devices in a circuit

As we already know, inductors can store energy for some period of time depending on the rate of decay, when the power supply is removed. This application is really seen in computer circuits where power supplies can be switched. The inductor helps the computer to manage shock as it were when the power supply is out.

Induction motors use Inductors in their circuitry.


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