Let’s talk about two electrical components that look similar but do very different jobs: inductors and transformers.
What’s an Inductor?
Think of an inductor as a temporary magnetic energy store. It’s basically a coil of wire, sometimes wrapped around a metal core.
Here’s what it does:
When current flows through, it builds up a magnetic field (storing energy temporarily)
When you try to change the current quickly, it fights back (releasing that stored energy)
It lets DC current pass through easily (after a brief start‑up moment)
It resists AC current, especially high‑frequency AC
Where you find them:
In power supplies, briefly holding energy
In filters, blocking noise
As “chokes” to suppress electrical interference
Simple rule: Inductors store energy in their own magnetic field while current flows.
What’s a Transformer?
Now imagine taking two inductors and putting them so close that their magnetic fields strongly interact. That’s a transformer.
Here’s what it does:
Transfers energy from one coil to another through a shared magnetic field
Can increase or decrease voltage — like a gearbox for electricity
Provides electrical isolation between circuits (depending on construction)
Only works with changing current (AC or pulses) — DC won’t transfer and can overheat it
Where you find them:
In phone chargers (stepping down voltage)
In power grids (stepping up voltage for long‑distance transmission)
In audio equipment (matching impedance)
Anywhere you need isolation or a change in voltage
Simple rule: Transformers transfer energy between circuits through a shared magnetic field.
The Big “Aha!” Moment
A transformer is essentially two (or more) inductors that are magnetically coupled.
If the coupling is tight, it’s an efficient transformer. If it’s loose, energy leaks and they act more like separate inductors.
That’s why real transformers aren’t perfect — there’s always some magnetic “leakage.”
Key Differences at a Glance
INDUCTOR:
Windings: One
Energy: Stores it (temporarily)
DC: Passes it (after a moment)
Voltage conversion: No
Isolation: No
TRANSFORMER:
Windings: Two or more
Energy: Transfers it (ideally stores very little; real transformers store small amounts temporarily in magnetizing and leakage inductance)
DC: Does not transfer
Voltage conversion: Yes
Isolation: Usually yes
How Do Transformer Windings “Talk”?
This is important: the windings don’t need to be electronically “tuned” to each other. They communicate purely through a shared, changing magnetic field.
Think of it like this:
The primary winding creates a changing magnetic field in the core.
That changing field passes through all windings on that core.
Every winding experiences the same changing field.
Each winding generates a voltage based on how many turns it has.
The frequency is set by the primary. If you pulse the primary 10 times per second, every secondary will see a 10 Hz signal — regardless of its number of turns. More turns = higher voltage, same frequency.
Real‑World Limits
Transformers work over a range of frequencies, but they’re not perfect everywhere:
Low frequencies (like 10 Hz):
Need huge, heavy cores
Often impractical for everyday use
Risk of core saturation
High frequencies (like 10 MHz):
Core materials lose efficiency
Parasitic capacitance and inductance dominate
Require specialized designs and materials
Simple Analogies
The Conveyor Belt:
Primary puts boxes (energy) on the belt (magnetic field)
Secondary takes boxes off the same belt
As long as the belt moves, energy transfers
The Gearbox:
A transformer is like a gearbox for electricity
Turns ratio = gear ratio
Input RPM (frequency) stays the same
Only the torque (voltage/current) changes
Bottom Line
An inductor is a solo artist temporarily storing energy in its own magnetic field.
A transformer is a team player transferring energy between circuits through a shared magnetic field.
Next time you plug in a phone charger, remember — that little block contains a high‑frequency transformer stepping voltage down thousands of times per second, all thanks to the physics of shared magnetic fields.
Understanding this basic difference helps make sense of everything from power supplies and audio gear to the entire electrical grid.
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