How Do Magnets Work?

Magnetism originates from quantum electron spin — a property with no classical analogy that generates a tiny magnetic dipole for each electron. The strongest continuous magnetic field ever produced reached 45 tesla at the National High Magnetic Field Laboratory in 2019, roughly 900,000 times stronger than Earth's magnetic field. The fridge magnet sticking to your refrigerator and the most powerful research magnet on Earth both operate on the same underlying physics.

Electron Spin: Where It All Starts

Every electron has an intrinsic property called spin — either "up" or "down." This isn't the electron physically rotating; it's a quantum mechanical property that has no everyday equivalent. But spin creates a magnetic moment: a tiny magnetic field associated with each electron.

In most materials, electrons come in pairs with opposite spins. The opposing magnetic moments cancel each other out, and the material has no net magnetism. In ferromagnetic materials — iron, nickel, cobalt — some electrons are unpaired. Their magnetic moments don't cancel, and under the right conditions they align.

Magnetic Domains

Inside a piece of iron, the aligned electrons form regions called magnetic domains — zones where all the microscopic magnetic moments point the same direction. An unmagnetized piece of iron has many domains, randomly oriented, so their fields cancel at the macro level.

When you place iron in a strong external magnetic field, the domains that are aligned with that field grow at the expense of misaligned domains. If enough domains align — and stay aligned when the field is removed — you have a permanent magnet. Heat a magnet above its Curie temperature (around 770°C for iron) and the thermal energy randomizes the domains. The magnet loses its magnetism instantly.

A permanent magnet's force comes not from anything actively "running" — it's a frozen alignment of quantum-scale electron properties, maintained indefinitely at room temperature.

Electromagnets

Moving electric charges generate magnetic fields — that's one of Maxwell's fundamental equations of electromagnetism. When current flows through a wire, it creates a circular magnetic field around the wire. Coil that wire into a solenoid and the fields add up, creating a strong field through the center of the coil.

The practical applications are everywhere: electric motors, MRI machines, particle accelerators, hard drives, maglev trains. The Circuit Builder game lets you experiment with how electrical circuits behave — the electromagnetic principles that govern circuits are the same ones governing every electromagnet.

Turn off the current, and the electromagnet's field disappears. That's the key difference from permanent magnets: controllability. MRI machines use superconducting electromagnets cooled to near absolute zero, which eliminates electrical resistance and allows enormous current — and enormous magnetic fields — without burning out.

Why Don't All Materials Stick to Magnets?

Most materials are diamagnetic — they slightly repel magnets because the external field induces opposing magnetic moments in their electrons. Wood, water, skin, plastic, copper — all diamagnetic. The repulsion is weak, but it's real.

Paramagnetic materials (aluminum, platinum, oxygen) are weakly attracted to magnets. Their unpaired electrons align with external fields, but the alignment is weak and disappears when the field is removed.

Only ferromagnetic materials (iron, nickel, cobalt, and some alloys) show the strong, persistent attraction most people associate with "magnetic." The difference is entirely about electron configuration and domain behavior at the quantum level. The Element Fusion game is worth exploring for understanding how atomic structure determines material properties — magnetism is just one result of electron arrangement.

The Strongest Magnets Ever Built

The 45-tesla continuous magnet at Florida State University requires 34 megawatts of power — enough to power a small city. It's used for physics and materials research that requires extreme field strengths. Pulsed magnets (not continuous) have reached 100 tesla for fractions of a second before the coils vaporize from the induced forces.

Neutron stars generate the most extreme magnetic fields in nature: up to 10^15 tesla in magnetar variants. By comparison, Earth's magnetic field at the surface is about 50 microtesla — 0.00005 tesla. The difference between a fridge magnet and a magnetar spans more than 20 orders of magnitude, all driven by the same quantum electron spin physics.

Magnetism and Electricity Are the Same Force

The deepest truth about magnetism is that it's not separate from electricity. Electromagnetism is a unified force — electricity and magnetism are two aspects of the same phenomenon, related by special relativity. A static electric charge creates an electric field. Move that charge, and you get a magnetic field. The distinction between "electric" and "magnetic" depends on your reference frame.

This connection is what makes how electricity works so directly relevant to understanding magnets. And how WiFi actually works — electromagnetic waves propagating through space — is another manifestation of the same underlying physics that makes your fridge magnet stick.

The Falling Sand physics sandbox lets you interact with simulated electromagnetic and material properties — not a rigorous model, but a good intuition builder for how particles and forces interact at scale.