Permanent vs Electromagnet vs Superconducting: The Three Main Types of Magnets
- Alisa Peters
- 12 minutes ago
- 4 min read
When I wrote the magneto post, I mentioned that magnetos are "the opposite of an electromagnet, where you apply current to the coil which creates a magnetic field”. Classic Alisa: explaining something by saying it's the opposite of something else I hadn't actually explained yet. I've also been casually referencing MRI machines as examples of precision magnetic applications across multiple posts without ever explaining what kind of magnet an MRI actually uses. It turns out, it's neither of the types we've covered. Turns out there are three meaningfully different kinds of magnets, and they are not interchangeable. Let's fix all of this at once. For more background on who I am and why this post exists, head over to Introduction to Alisa Learns about Magnets. To deep dive into the different types of magnets, read on!
💡 TLDR: What we're covering
Permanent Magnets: Always on, incredibly reliable, and require zero external power.
Electromagnets: Switchable and adjustable, but require a continuous stream of electrical power.
Superconducting Magnets: Electromagnets cooled to near absolute zero, capable of generating massive magnetic fields nothing else can match.
Permanent Magnets: The Always-on Workhorses
You already know this one, even if you didn't know the name. A permanent magnet is a material whose internal magnetic domains - regions where the atoms' magnetic fields all point in the same direction - have been aligned and locked in place during manufacturing. No external power source required. It just sits there being magnetic, indefinitely, as long as you don't heat it past its Curie temperature (the temperature at which thermal energy overwhelms the alignment and the magnetism collapses, around 310°C for neodymium, higher for other materials) or physically destroy it.
All the magnets we've discussed throughout this series - NdFeB, SmCo, Alnico, ceramic - are permanent magnets. They're the workhorses of motors, sensors, speakers, and assemblies where you need a reliable, always-present magnetic field with no ongoing energy cost.
The catch: you can't turn them off, and you can't dynamically adjust their strength.
Electromagnets: Controllable, On-demand Fields
An electromagnet is the flip side. Wrap wire around an iron core, run electrical current through it, and a magnetic field appears. Stop the current and the field disappears. The strength of the field is proportional to how much current you push through the coil and how many times the wire wraps around the core: double the current, roughly double the field.
This gives you two capabilities permanent magnets don't have: you can switch it on and off, and you can control the strength.
Junkyards use massive electromagnets to pick up cars and drop them by cutting the power.
Industrial automation relies on them to clamp metal workpieces during high-precision machining and release them cleanly.
Automotive starter motors (like your car's) use an electromagnet to engage the starter gear, then quickly disengage it.
As I mentioned in the magneto post, electromagnetic induction, the principle that a changing magnetic field creates electrical current in a nearby wire, is what the magneto exploits. A magneto spins a permanent magnet to generate current; an electromagnet uses electrical current to create the field. Two sides of the same coin.
The catch: you need continuous power to maintain the field, and all that current moving through wire generates heat. At very high field strengths, the energy required and the cooling required become impractical fast.
Superconducting Magnets: The Ultimate High-Field Powerhouses
Yes, there is a third kind of magnet. And this one earned a genuine 🤯 from me.
A superconducting magnet is, at its core, still an electromagnet. But the wire is made from superconducting materials, which, when cooled to temperatures near absolute zero (around -269°C, usually achieved using liquid helium), have exactly zero electrical resistance. Not low resistance. Zero.
Because there is no resistance, no energy is wasted as heat. Once you establish the electrical current in a superconducting coil, it circulates essentially forever without needing a continuous power supply to maintain it. You can run enormous currents and generate magnetic fields 10,000 to 100,000 times stronger than Earth's magnetic field; fields that no permanent magnet and no conventional electromagnet can come close to.
Where do we use these absolute monsters?
Medical Imaging: The MRI machine at your local hospital relies on a superconducting magnet to get those razor-sharp internal scans.
Particle Physics: The massive particle accelerators at CERN, which discovered the Higgs boson, run on superconducting tracks.
Fusion Energy: Next-generation nuclear fusion reactors (like ITER in France and Commonwealth Fusion's SPARC project in Massachusetts) use them to contain 100-million-degree plasma. A single machine houses temperatures hotter than the sun, just inches away from magnets cooled to colder than deep space. The range of temperatures involved in a single fusion reactor is probably the most extreme thing I have ever tried to picture.
The catch: keeping anything at -269°C is expensive, infrastructure-intensive, and not portable. Superconducting magnets are for applications where nothing else will do.
Which Magnet Do You Need?
Magnet Type | Power Required? | Field Controllable? | Main Benefit | Common Applications |
Permanent | No | No | Always-on, highly reliable, zero operating cost | Motors, automotive sensors, consumer electronics, speakers |
Electromagnet | Yes (Continuous) | Yes | Can be turned on/off and dialed up or down | Industrial lifting, automation clamping, starter solenoids |
Superconducting | Yes (For Cooling) | Yes (During setup) | Generates extreme, ultra-powerful magnetic fields | Hospital MRI machines, particle accelerators, fusion reactors |
QT Magnetic Solutions works primarily in the permanent magnet space, designing and manufacturing precision assemblies for applications that need exactly the right field in exactly the right place. But understanding how all three types compare is what makes it possible to make intelligent choices about which technology is right for a given application.
Trying to figure out which magnetic property or assembly configuration is right for your next project? Contact the experts at QT Magnetic Solutions. (I need to go cool my own brain down to absolute zero after writing about all that physics.)