What Is Inductance? Inductor Basics for Real-World Circuits

If you’re still building your foundation in basic electricity, start with this beginner-friendly overview: 🔹 “Electricity 101: The Complete Beginner’s Guide to How Power Really Works”
After reading it, the concepts in this article will make a lot more sense.

Watch first: what is inductance and how does it affect a circuit?

This short video walks you through what is inductance in a very visual way – how current creates a magnetic field around a conductor, and how that magnetic field “pushes back” on the circuit when things change.

If you’ve ever asked yourself, “What exactly is inductance? What is this inductor even doing in my circuit?” this is for you.

Watch the video first, then come back to this article. The diagrams and examples below will help you see what inductance is doing in power supplies, wireless charging, and everyday electronics.

If you just typed “what is inductance” into a search bar, you’re in the right place – this guide is written to answer that question in plain English, with real-world examples.

What is inductance? The plain-English version

A lot of people first meet inductors in a textbook and immediately ask:

“What is inductance, exactly? And why do I keep seeing these coils everywhere?”

If you think of a circuit as a water pipe, an inductor is a little like a water tank that hates sudden changes in flow. It doesn’t want the flow to jump from low to high in an instant, or from high to zero in one click.

Inductance is a property of a circuit – and also a family of components – that shows up all over:

• power supplies
• audio filters
• wireless charging coils
• power-management chips inside your phone and laptop

Put simply:

• When current changes, a magnetic field grows or shrinks around the conductor.
• When that magnetic field changes, it creates a voltage that fights back against the change in current.

So inductors are really good at two things:

• resisting sudden changes in current, and
• storing energy in a magnetic field and releasing it later

That’s why whenever you see filtering, smoothing, or wireless energy transfer, you almost always see inductors nearby.

The basic physics: from coil of wire to magnetic energy

To really answer “what is inductance,” it helps to look at the structure.

Most inductors you see on a board are just insulated copper wire wound into a coil. That coil is the inductor.

From Faraday’s Law of Induction, a few key things happen. If you want a more textbook-style explanation, you can also check this inductance tutorial on All About Circuits.

• When current flows through the coil, it creates a magnetic field around it.
• When the current starts to increase or decrease, that magnetic field also changes.
• A changing magnetic field induces a voltage (EMF) in the wire, and that induced voltage pushes against the original change in current.

This “your own current change creates a voltage that fights back” behavior is called self-induction.

That’s the root of inductance: the coil builds a magnetic field as current changes, and that field pushes back on any attempt to change the current too quickly.

In other words: an inductor is that friend who always says, “Slow down. One step at a time.”

Two key behaviors of an inductor

1. It resists changes in current
   • When current suddenly wants to jump up, the inductor generates a reverse voltage that pushes it down.
   • When current suddenly wants to drop to zero, the inductor generates a forward voltage to keep current flowing a bit longer.
   So in simple terms: inductors dislike “instant changes” and prefer that current ramps up and down more gently.
2. It stores energy in a magnetic field
   • While current is flowing, part of the energy is stored as a magnetic field around the inductor.
   • When the circuit changes (for example, a switch opens), the inductor releases that magnetic energy back into the circuit.
   That’s why in switch-mode power supplies and motor drivers, you often see inductors paired with diodes and capacitors – they’re all helping energy flow in controlled ways instead of in violent spikes.

The math and units: V = L × (dI/dt)

The size of an inductor is measured in henry (H). In real circuits you’ll usually see millihenry (mH) or microhenry (µH).

The classic equation that describes inductance is also the compact way engineers answer what is inductance in a changing-current circuit:

V = L × (dI/dt)

Where:

• V = the induced voltage across the inductor (in volts)
• L = the inductance (in henry)
• dI/dt = how fast the current is changing with respect to time (the rate of change of current)

From this one formula you can see two important things:

• The more “aggressive” the current change, the larger dI/dt becomes, and the larger the induced voltage will be.
• For the same rate of change, a larger inductance L will produce a larger voltage.

This is why inductors matter so much in fast switching circuits: when you switch current on and off quickly, dI/dt is huge, so the voltages and spikes can be huge too if you don’t design around them.

How does inductance affect a circuit? Four common scenarios

In real designs, inductors are not just abstract symbols. They quietly control how your home, office, and lab gear behaves.

Here are four everyday scenarios where inductance shows up. When you understand what is inductance doing in each of these cases, circuit design starts to feel much less mysterious.

1. Filtering: cleaning up noisy power

One big trait of inductors is that they are more sensitive to high-frequency changes than to slow changes. That makes them great for filters.

• Low-pass filters
  Combine an inductor with a capacitor and you can let smooth DC pass while stripping away high-frequency noise. Your phone charger, Wi-Fi router, monitor power supply, and many other adapters all rely on this kind of filtering.
• High-pass filters
  With a different configuration, an inductor-capacitor pair can pass high-frequency signals and block low-frequency ones. You’ll see this in audio crossovers and RF (radio-frequency) circuits.

2. Power regulation: the star of switching power supplies

In almost every DC-DC converter (buck, boost, buck-boost, and so on), an inductor is one of the main characters.

It takes turns storing energy while a switch is on, and releasing energy when the switch is off. That back-and-forth is what makes the output voltage smoother and more stable.

• Boost converters
  The inductor stores energy while the switch is on, then dumps that stored energy into the output when the switch turns off. Done right, the output voltage ends up higher than the input.
• Buck converters
  Here, the inductor’s job is to turn a very “choppy” pulsed current into a smoother one. That smoothing protects whatever is downstream from big current swings and voltage ripple.

Whenever you see a compact switching regulator on a board, that chunky little inductor nearby is doing a lot of heavy lifting.

3. Inductive sensors: detecting metal and motion

Inductors are also used as sensors. If you put a coil near metal or magnetic material, its inductance changes – and your circuit can detect that.

Common examples include:

• Metal detectors
  A coil in the detector senses changes in inductance when there’s metal under the ground or in an object.
• Wireless charging pads
  The “coil” inside a wireless charging pad is basically an inductor. Its changing magnetic field induces current in the coil inside your phone, which then charges the battery.
• Proximity and position sensors
  Industrial gear often uses inductive sensors to detect when a metal part reaches a certain position, with no physical contact.

4. Wireless communication and antennas: LC resonant circuits

In RF and wireless designs, inductors and capacitors are often paired into LC resonant circuits. By choosing the right L and C values, you tune the circuit to a particular resonant frequency – basically choosing what band of signals you care about.

You’ll see this in:

• AM/FM radios and other receivers – adjusting inductance or capacitance lets you “tune” different stations.
• RFID tags and readers – both sides use coils and inductance.
• Cell-phone and Wi-Fi antennas – tiny inductors and matching networks help antennas work efficiently at specific frequencies.

Once you know what inductance does, those little coils and SMD inductors on RF boards start to make a lot more sense.

Try this at home (or in a simulator): feel how inductance slows current change

This next one is more of a concept demo than a lab exercise. If you’re not comfortable wiring things up, it’s much safer to start with a circuit simulator like Falstad Circuit Simulator or LTspice.

Experiment: observe how an inductor resists current changes

📌 Parts (conceptual):

• A battery (for example 3 V or 5 V)
• An LED with a series resistor
• An inductor around 100 mH
• A mechanical switch or momentary push button

📌 Basic steps:

1. Wire the battery, inductor, LED (plus its resistor), and switch in series.
2. Quickly toggle the switch on and off and watch how the LED turns on and off.
3. Now repeat the experiment without the inductor – just battery, resistor, LED, and switch in series – and compare the behavior.

🔎 What to notice

With the inductor in the circuit, the LED usually feels a bit slower to respond. The changes in brightness aren’t as sharp, because the inductor doesn’t “like” the current to jump instantly.

Without the inductor, the LED snaps on and off more abruptly.

That difference is your eyes seeing inductance resisting changes in current.

Common inductor types: same idea, different packages

We call them all “inductors,” but their shapes and internal structures vary a lot depending on the job.

Here’s a quick comparison:

Even if they look very different on the board, they’re all playing with the same underlying idea: storing energy in a magnetic field and shaping how current changes over time.

Inductance FAQ

Wrap-up: understand inductance, understand your circuit’s “mood”

So, if someone asks you again, “What is inductance?”, you can answer it in one sentence:

Inductance is a circuit’s tendency to resist changes in current by storing energy in a magnetic field.

Inductors don’t like current to slam on the gas or stomp on the brakes. They smooth things out by absorbing energy when current rises and releasing it when current falls.

From noise filtering and power regulation to wireless charging and RF tuning, any time you see changing current and magnetic fields, inductance is involved. Once you get this, you stop memorizing inductor symbols and start seeing what job each inductor is doing in the bigger system.

If you want to go further into transformers, motors, EMI filters, or wireless communication, this inductance foundation will keep paying off.

📌 Further reading

🔹 DIY Guide to Voltage and Current: Unlock the Basics
Start from voltage, current, and power and turn “invisible electricity” into something you can reason about in everyday language. This is the foundation you want before diving deeper into inductors.

🔹 What Do Capacitors Actually Do? How They Store and Release Energy
Read this alongside inductors and you’ll really feel the “inductors manage current, capacitors manage voltage” partnership. It also sets you up to understand LC filters and oscillators.

🔹 How LC Oscillators Work (coming soon)
We’ll jump into wireless and RF land and see how inductors and capacitors together set the frequency of oscillators and tuned circuits.

🔹 How Inductance Powers Wireless Charging (coming soon)
We’ll start from your phone’s wireless charging pad and unpack how coils, magnetic fields, and efficiency all fit together.

💡 Still confused about any part of inductance?
Drop a question in the comments or subscribe to the blog. I’ll keep building out this whole chain – inductors, transformers, motors, and EMI filters – so you can grow a solid, practical understanding of how real-world circuits behave.