A magnet reaches out and grabs things without touching them. The reach is invisible — until you scatter iron filings and the whole hidden shape leaps into view.
Make it appearA magnet can pull a paperclip toward it — or push another magnet away — across a gap of empty air, without ever touching it. It does this through an invisible magnetic field: a region of force wrapped around the magnet, its own little area of influence.
You can't see the field with your eyes. But you can absolutely see what it does — and with a sprinkle of iron filings you can even trace its exact shape. That is the whole adventure on this page: making the invisible visible, then learning to read it.
Pick up a straight bar magnet and you'll find its power isn't spread evenly along it. The pull is concentrated at the two ends, and those two ends are not the same. We call them poles — one is the north pole (usually marked N) and the other is the south pole (marked S). A magnet always has both. There is no such thing as a magnet with only a north pole, the way there's no stick with only one end.
Here's the part that surprises people: cut a bar magnet cleanly in half and you don't get a lonely north piece and a lonely south piece. You get two smaller magnets, each with its own brand-new north and south. Snap those in half again and you get four, each complete. No matter how small you go, every piece keeps both poles. Two poles, always — that's rule number one, and the whole rest of the page hangs off it.
Bring two magnets close and they'll either spring apart or rush together — and which one happens depends entirely on which poles are facing. The rule is short enough to chant:
It's a little like the rule for friends and arguments: two of the same kind clash, two different kinds click together. You'll get to feel this for yourself in a moment — there's a demo below where you drag one magnet toward another and watch them push or pull. For now, just hold onto the rhyme: same pushes, different pulls.
So how does one magnet "know" another is nearby, across a gap of air? The answer is the magnetic field — the invisible region around a magnet where its push and pull can be felt. Step a paperclip into that region and it gets tugged; step it far enough away and nothing happens at all. The field has a shape, and an edge, like a bubble of influence the magnet carries with it.
The field is invisible, but its effects are not — and there's a beautiful trick for tracing it. Scatter tiny slivers of iron, called iron filings, around a magnet. Each filing is so small and light that the field gently turns it, and each one lines up pointing along the field right where it sits. Thousands of them together draw the field's hidden shape as curved field lines that sweep from the north pole around to the south pole. Suddenly you're staring straight at something invisible.
Drag the magnet below and watch the filings re-arrange themselves live. Notice how they crowd together and grow brightest at the two poles — that's where the field is strongest. Add a second magnet to see what happens when two fields share the same space.
The filings trace curved lines from N to S — densest and brightest at the poles, where the field grips hardest.
Look closely and you'll see the field lines always loop out of the north pole, curve through the air, and dive back into the south pole. They never cross, and they bunch up tightest right at the poles. That bunching is the picture of strength: where the lines are crowded, the field is strong; where they spread out and thin, the field is weak. Move a paperclip into the crowded part near a pole and it leaps; hold it out in the thin part and it barely stirs.
The field also has an edge — it fades fast as you move away. That's why a fridge magnet only holds while it's touching the door, or almost: its little field is strong right at the surface but withers within a centimetre or two. Slide a sheet of paper behind it and it still grips, because the field reaches straight through paper to the steel beyond. Add a second sheet, then a third, and at some point the door is just too far inside the thinning field, and the magnet slips. Same magnet, same poles — you've simply walked the steel out past the strong part of the field.
Drag the right-hand magnet toward the left one. Flip the switch to choose which poles meet. Watch the force arrows grow as the gap shrinks — then let go and see them push apart or snap together.
Two north poles are facing — alike, so they repel. Drag them close and feel the push grow.
The harder you crowd two like poles together, the stronger the push back — the field is fighting you, and it never gives up. Opposite poles do the reverse: the closer they get, the harder they pull, until they clack together and hold. Same rule, every single time, no matter the magnets' size or shape.
Try sticking a magnet to everything in your kitchen and you'll make a surprising discovery: most things ignore it completely. A magnet pulls only on a short list of magnetic materials — chiefly iron, steel (which is mostly iron), nickel, and cobalt. That's why magnets cling to the fridge door, paperclips, and tin cans: there's iron or steel inside them.
Here's the trap almost everyone falls into: thinking that "metal" and "magnetic" mean the same thing. They don't. Plenty of metals are not magnetic at all. An aluminium drink can, a copper wire, a gold ring, a silver spoon — all metals, and a magnet slides right past every one of them. So it isn't "is it metal?" that matters; it's "is it one of the special metals?"
And non-metals? Forget it. Plastic, wood, glass, paper, water, your hand — none of them feel a magnet's pull. (That's exactly why a magnet still works through a paper sheet or a plastic fridge cover: the field passes straight through the stuff in between and grabs the iron on the other side.)
This pickiness is genuinely useful. Recycling plants tip a river of mixed rubbish past a powerful magnet: steel cans jump out and get pulled aside, while aluminium cans, plastic, and glass sail straight past untouched. With one magnet the machine sorts steel from everything else, no hands required. So next time a magnet refuses to stick to something shiny, you're not doing it wrong — you've just found one of the many metals that simply doesn't care about magnets at all.
Here's a fact that should feel a little wild: the whole planet behaves like one enormous bar magnet. Deep in its core, churning molten metal creates a magnetic field so big it stretches far out into space and wraps the entire Earth in its area of influence. We are all standing inside a magnet's field right now.
That's the secret behind a compass. A compass needle is just a tiny, lightweight magnet balanced so it can spin freely. Like any magnet, it lines itself up with the field it sits in — and the field it sits in is Earth's. So the needle swings around and settles pointing roughly north–south, every time, anywhere on the planet. That's not magic and it's not the needle "finding" anything clever; it's the same "magnets line up with a field" rule you watched the iron filings obey, just on a planet-sized scale. Sailors and hikers have trusted that quiet little needle to find their way for centuries.
The magnets so far are permanent magnets — they're magnetic all the time, whether you like it or not. But there's a second kind that's just as important, and it hints at one of the deepest connections in all of physics: moving electricity makes magnetism.
Wrap a wire into a coil and run an electric current through it, and the coil becomes a magnet — with its own north and south poles and its own field — for exactly as long as the current flows. Switch the current off and the magnetism vanishes. That's an electromagnet, and it's how a giant crane in a scrapyard can grab a whole car, lift it, and drop it on command. We'll pull that idea wide open another day; for now, just tuck away the clue that electricity and magnetism are secretly two faces of the same thing.
"If it's metal, a magnet will stick to it."
Only a few metals are magnetic — iron, steel, nickel, and cobalt. Most metals, like aluminium, copper, gold, and silver, feel nothing at all. "Metal" does not mean "magnetic."
"The bigger the magnet, the stronger it always is."
Size isn't strength. A small modern magnet can easily out-pull a much bigger old one — what matters is the material and how it's made. And remember: a magnet's pull is concentrated at its poles, so a small magnet held pole-on can grip harder than a big one held the wrong way.
Four quick questions. Tap an answer to see if it sticks.
Every magnet has a north and a south. Like poles repel; opposites attract.
A region of force wraps each magnet — strongest at the poles. Iron filings reveal its shape.
It grabs only iron, steel, nickel, and cobalt — not all metals. Even Earth is a giant magnet.