In the previous article, we learned that a capacitor stores electrical energy in the form of an electric field. An inductor is another energy-storing component, but it stores energy in a completely different way. Instead of storing energy in an electric field, an inductor stores energy in a magnetic field.
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Although capacitors and inductors are both passive components that store energy, they behave very differently in a circuit. In this article, you’ll learn what an inductor is, how it works, why it resists sudden changes in current, and where inductors are commonly used.
What is an inductor?
An inductor is a passive two-terminal electronic component that stores electrical energy in the form of a magnetic field.
Whenever electric current flows through an inductor, a magnetic field is created around it. This magnetic field stores energy as long as current continues to flow. When the current decreases or stops, the magnetic field collapses and the stored energy is released back into the circuit.
Unlike a capacitor, which stores energy in an electric field, an inductor stores energy in a magnetic field.
Why do we need an inductor?
If both capacitors and inductors store energy, why do we need two different components?
The answer lies in how they behave in a circuit.
One of the most important properties of a capacitor is that it resists sudden changes in voltage. Similarly, one of the most important properties of an inductor is that it resists sudden changes in current.
This means the current through an inductor cannot change instantly. Whenever the current tries to increase or decrease rapidly, the inductor opposes that change by generating a voltage across its terminals. This property is known as self-induction.
Because of this behavior, inductors are widely used in power supplies, filters, motors, and many other electronic circuits.
How does an inductor work?
Whenever electric current flows through a wire, it produces a magnetic field around the wire.
If the wire is wound into a coil, the magnetic fields produced by each turn combine, creating a much stronger magnetic field. As a result, the coil can store more energy than a straight wire.
To increase the magnetic field even further, many inductors use an iron or ferrite core inside the coil. These materials concentrate the magnetic field, allowing the inductor to store much more energy.
This is why most practical inductors look like coils wound around a core rather than a simple spring-shaped wire.
Inductance
The ability of an inductor to store energy in its magnetic field is called inductance.
Inductance is represented by the symbol L and is measured in henry (H).
The inductance of a coil depends on several factors, including the number of turns, the shape of the coil, and the material used for the core.
In general, increasing the number of turns or using an iron or ferrite core increases the inductance, allowing the inductor to store more energy.
Air-core and iron-core inductors
An inductor can have either an air core or a magnetic core.
An air-core inductor is simply a coil of wire with air inside it. These inductors have relatively low inductance and are commonly used in high-frequency applications.
An iron-core or ferrite-core inductor contains a magnetic core inside the coil. The core strengthens the magnetic field, increasing the inductance and allowing the inductor to store more energy.
Most inductors used in power supplies and electronic circuits are of this type.
Other names for an inductor:
Depending on the application, an inductor may also be referred to as a:
- Coil
- Choke
- Reactor
Although the names differ, they all refer to an inductor being used for a specific purpose.
Applications of inductors
Inductors are used in a wide variety of electronic and electrical systems.
Energy storage
One of the primary applications of an inductor is temporary energy storage. Switching power supplies, such as buck and boost converters, store energy in an inductor and then release it to efficiently regulate the output voltage.
Filters
Inductors are commonly used together with capacitors to remove unwanted noise and ripple from power supplies.
For example, after AC is converted into DC using a rectifier, the output still contains small voltage fluctuations. An inductor, along with a capacitor, helps smooth these fluctuations and produce a cleaner DC output.
When an inductor is used mainly to block high-frequency noise, it is often called a choke.
Transformers
A transformer consists of two or more coils wound around a common magnetic core.
By transferring energy from one coil to another through a changing magnetic field, transformers can step voltage up or down. This is why transformers are widely used in power supplies and electrical distribution systems.
Induction motors
Inductors also play an important role in induction motors. The coils inside the motor create rotating magnetic fields that produce motion, allowing the motor to convert electrical energy into mechanical energy.
Summary
An inductor is a passive component that stores energy in the form of a magnetic field. Unlike a capacitor, which resists sudden changes in voltage, an inductor resists sudden changes in current. This unique property makes inductors essential in power supplies, filters, transformers, and electric motors.
As you continue learning electronics, you’ll find inductors in many practical circuits, especially wherever energy needs to be stored temporarily or current needs to be controlled smoothly.