Electrical inductance is one of the fundamental properties of electromagnetism. It plays a crucial role in circuit behavior, especially where signal control, power conversion, and noise suppression are required. Inductors—components that exhibit inductance—are widely used in everything from power supplies and motors to RF systems and consumer electronics. They store energy in a magnetic field when electrical current flows through them, and this simple yet powerful property makes them indispensable in both everyday gadgets and complex industrial machinery.
But what exactly is inductance, and how does it function? For many, the concept may initially appear abstract or overly technical. However, with a clear explanation, it becomes a straightforward and essential concept in electronics. Understanding inductance not only helps clarify the fundamentals of circuit behavior, but also reveals how energy is managed and controlled in a wide range of systems—from everyday consumer electronics to industrial equipment.
In the sections below, we’ll define electrical inductance, describe how it works, and explain its practical function.This will help you understand how inductance fits into the broader context of electrical circuits and why it’s critical in designing reliable and efficient electronic systems
What Is Electrical Inductance and How Does It Work?
Electrical inductance (L) is a property of an electrical conductor, such as a wire, that causes it to oppose changes in the electric current flowing through it. So what does this mean? Think of it as the electrical version of inertia. Just as inertia resists changes in motion, inductance resists changes in the electric current.
When you push an electric current through a wire or a coil, it creates a magnetic field around it. The strength of this magnetic field will depend on the magnitude of the current. If you try to change the amount of current flowing through the coil — whether you try to increase or decrease it — the magnetic field changes, too. But the coil doesn’t like these changes and tries to resist them. This induces a voltage in the wire that opposes the change in current. The effect here is inductance.
The electronic component that adds inductance to a circuit is called an inductor. Inductors are simple components consisting of a coil of wire, often wound around a core made of air, iron, or another magnetic material. Inductance allows the conductor to store energy in the magnetic field created by the current. The energy required to set up this magnetic field is released when the field collapses.
This property is super useful because it helps smooth out the current in electrical devices, preventing sudden spikes or drops that could cause damage.
Inductance is measured in henries (H), where 1 henry equals the amount of inductance that induces 1 volt of electromotive force when the current changes at a rate of 1 ampere per second.
Types of Inductance and How They Are Used
There are two main types of inductance: self-inductance and mutual inductance. Let’s take a look at these two, how they work, and how they’re different.
What Is Self-Inductance?
Self-inductance happens when a single coil experiences a change in current or magnetic flux. Imagine you have a coil of wire, like a spring. Something interesting happens when you start sending an electric current through the wire. The magnetic field around the coil begins to grow. This magnetic field is directly related to the amount of current flowing through the coil. We can say that the magnetic flux (the magnetic field passing through the coil) is proportional to the current. In other words, as the current increases, the magnetic field increases predictably.
The equation that describes this relationship looks like this:
= L I
This equation tells us that the magnetic flux () is equal to the self-inductance (L) times the current (I).
Now, what is self-inductance? It’s a measure of how good the coil is at creating a magnetic field for a given amount of current. The self-inductance depends on a few factors:
- The cross-sectional area of the coil (bigger area = more inductance).
- The material’s permeability inside the coil (how easily it can be magnetized).
- The number of turns or loops in the coil (more turns = more inductance).
The changes in the induced voltage (V) in the coil, caused by the changing current, are:
V = -LdIdt
where, dIdt is the rate of change of the current. The negative sign shows that the induced voltage opposes the change in current (Lenz’s Law).
The self-inductance formula, which gives L in terms of the coil’s physical properties, is:
L = NI
Where:
- L is the self-inductance in henries (H).
- 𝑁 is the number of turns in the coil.
- Φ is the magnetic flux in webers (Wb) or V·s.
- 𝐼 is the current in amperes (A).
Chokes are a good example of self-inductance in electrical equipment. Chokes are a type of inductor specifically designed to block or “choke” high-frequency AC signals while allowing DC or low-frequency AC signals to pass. They make use of inductance to filter out unwanted high-frequency noise or interference in electronic circuits. When high-frequency AC attempts to pass through a choke, the inductor creates a strong opposing voltage due to its high inductive reactance at these frequencies, thereby blocking the AC signal. In contrast, for low-frequency AC or DC, the inductive reactance is much lower, allowing these signals to pass through more easily.
What Is Mutual Inductance?
Mutual inductance happens when a change in the current in one coil creates a voltage in a nearby coil because they share a magnetic field. Imagine you have two coils of wire, let’s call them Coil P (the primary coil) and Coil S (the secondary coil). Coil P is connected to a battery and a switch, while Coil S is connected to a galvanometer (a device that measures small currents).
Now, when you turn the switch on and off, the current in Coil P changes. This changing current creates a changing magnetic field around Coil P. Since Coil S is nearby, this changing magnetic field also affects it. As the magnetic field through Coil S changes, it induces a voltage (or electromotive force) in Coil S. This voltage is created so that it opposes the change in current in Coil P. This whole process is called mutual inductance.
The phenomenon of mutual inductance can be described with the equation:
Vs = -M.dIpdt
Where:
- Vs is the induced voltage in the secondary coil (Coil S).
- M is the mutual inductance between the two coils.
- dIpdt is the rate of change of current in the primary coil (Coil P).
The mutual inductance M depends on several factors: permeability of free space (0), relative permeability (r), number of turns in the coils (N), the cross-sectional area of the coils (A), and the length of the coils (l).
The formula for mutual inductance is:
M = 0.r .N.Al
An everyday example of mutual inductance is in transformers. The mutual inductance between the two coils in a transformer allows it to step up (increase) or step down (decrease) the voltage as needed. This helps transmit electrical power over long distances and provides the correct voltage to electronic devices.
What Are the Differences Between Self-Inductance and Mutual Inductance?
I’ve already discussed what self and mutual inductance are, and Table 1 below shows you a summary of the differences between the two:
| Self Inductance | Mutual Inductance |
| The coil resists changes in its own current by inducing a voltage within itself. | One coil resists changes in the current of a nearby coil by inducing a voltage in the other coil. |
| The induced voltage opposes the increase in current within the same coil. | The induced voltage in the neighboring coil opposes the increase in current in the original coil. |
| The induced voltage opposes the decrease in current within the same coil. | The induced voltage in the neighboring coil opposes the decrease in current in the original coil. |
What Are the Uses for Electrical Inductance?
Let’s take a look at some of the cool ways inductors are used:
1. Power Supplies
Ever wonder how your phone charges safely? Inductors in power supplies help keep the voltage and current stable. They filter out noise and smooth out any fluctuations, ensuring your devices get a steady and safe power supply. This not only protects your gadgets but also keeps them running efficiently.
2. Filters
Inductors are great for filtering out unwanted noise in electronic signals. They’re often used with capacitors and resistors to create filters in things like audio systems and radios. An inductor can act as a low-pass filter, blocking high-frequency noise and letting important low-frequency signals through. This helps ensure that what you hear or see is clear and free of static.
3. Transformers
Transformers use mutual inductance to step up the voltage for long-distance power transmission and step it down for safe use in homes and businesses. Without transformers, our electrical grid wouldn’t be nearly as efficient or safe.
4. Motors
Inductive motors use inductors to convert electrical energy into mechanical motion. These motors are found in many household appliances, like fans and washing machines. They work by creating a rotating magnetic field that makes the motor spin. The cool part is that they don’t need electrical contacts between the moving parts, which makes them super reliable and durable.
5. Sensors
Ever notice how traffic lights seem to know when you’re waiting at an intersection? That’s thanks to inductive sensors. Inductive sensors use inductors to detect metal objects or magnetic fields without needing to make physical contact. You’ll find these sensors at traffic lights, where they detect cars waiting at intersections. They’re also used in industrial settings to monitor machinery. These sensors are reliable and last a long time because they don’t wear out from physical contact.
6. Energy Storage
Inductors can store energy in a magnetic field, which is handy in power supplies for computers and other devices. They can hold energy temporarily and release it when needed to ensure a steady power supply. This is particularly useful in switch-mode power supplies, which are common in PCs. These power supplies use inductors to manage energy flow, making sure your device gets just the right amount of power.
How Inductance Affects the Impedance in AC Circuits
Yes, inductance affects the impedance of an AC circuit. Impedance is like resistance but for AC circuits. When you have an inductor in the circuit, it resists changes in current because it creates a magnetic field. This resistance is called inductive reactance (XL), and it adds to the circuit’s impedance. Inductive reactance increases with frequency and is defined by:
XL = 2πfL
Where:
- XL = inductive reactance (ohms)
- f = frequency (Hz)
- L = inductance (H)
Higher frequencies result in greater opposition to current changes, making inductors effective for low-pass filtering and tuning circuits.
What Is the Difference Between Electrical Capacitance and Electrical Inductance?
Capacitance and inductance are two key principles in electrical circuits.
Capacitance is all about storing energy in an electric field. Picture a capacitor like a tiny battery that separately holds positive and negative charges on two plates. This setup helps capacitors smooth out voltage changes and filter high-frequency signals, keeping your power supply steady.
Inductance is about storing energy in a magnetic field created by current flowing through a coil. Think of an inductor as a coil of wire that resists changes in current. Inductors are perfect for filtering out unwanted noise in AC circuits and are essential in transformers and motors, which convert electrical energy into mechanical motion.
Essentially, capacitors store energy electrically and resist changes in voltage, while inductors store energy magnetically and resist changes in current. Capacitors are great for high-frequency filtering, and inductors are your go-to for low-frequency tasks. Both are complementary components in electronic design.
