Every magnet has a north and a south pole. Its invisible field loops from one to the other, and anything with iron inside gets pulled along the lines.
🧲 A magnet is a rock or metal that pulls iron.
📎 Put a paper clip near a magnet. Click! It jumps and sticks.
🔴 Every magnet has two ends. Turn two magnets one way and they hug. Turn them the other way and they push apart.
What is a magnet?
A magnet is a piece of metal or rock with a special pull. It pulls on iron. Paper clips, nails, and most fridge doors have iron in them, so they stick.
Why does it have two ends?
Every magnet has a north end and a south end. We call them poles. A north pole and a south pole pull together. Two north poles push apart. Try it with two fridge magnets!
Does it pull everything?
No. It does not pull paper, wood, plastic, or a penny. A magnet only grabs things with iron, nickel, or cobalt inside.
Is the Earth a magnet?
Yes! Deep inside the Earth is hot, moving iron. It makes the whole planet one giant magnet. A compass needle is a tiny magnet, and it turns to point north.
Two Ends, Two Poles
Every magnet has a north pole and a south pole. Opposite poles attract: north pulls south. Matching poles repel: north pushes north away. If you cut a magnet in half, you do not get a lone north and a lone south. You get two smaller magnets, each with both poles. Scientists have never found a magnet with only one pole.
What Makes Iron Stick
Iron does not start out as a magnet, so why does it jump to one? Think of iron as full of tiny magnets called domains, pointing every which way, so they cancel out. Bring a magnet close and its pull swings the domains to line up. For a moment, the iron becomes a magnet too, with its south pole facing the magnet's north. Opposite poles attract, so click. Stroke a needle with a magnet in the same direction many times and the domains stay lined up. You have made a magnet.
The Biggest Magnet You Know
Earth is a magnet. Far below your feet, liquid iron swirls around a solid iron core, and that moving metal makes a magnetic field that wraps the whole planet. A compass needle is a small magnet balanced on a pin, so it swings to line up with Earth's field. That is how sailors found their way for a thousand years before satellites.
Magnets You Can Switch On
Electricity makes magnetism too. Wrap wire around an iron nail, connect a battery, and the nail becomes a magnet until you disconnect it. This is an electromagnet. Scrapyard cranes use giant ones to lift cars, and the motors in fans, toys, and electric cars all spin because of magnets.
Try This!
Collect ten small things and guess which will stick to a fridge magnet. Then test them. Next, put a magnet under a sheet of paper, sprinkle iron filings or tiny bits of steel wool on top, and tap. The pattern you see is the shape of the magnetic field.
Where Magnetism Comes From
Every magnet, from a fridge magnet to the Earth, is made by moving electric charge. The key movers are electrons. Each electron behaves like a tiny bar magnet with its own north and south, a property physicists call spin, and every atom's electrons also circle the nucleus, which adds a little more. In most atoms the electrons pair off with their spins pointing opposite ways, so the tiny magnets cancel and the material barely notices a magnet at all. That is why a wooden spoon, a glass jar, and a copper coin all ignore the magnet on your fridge.
Iron is different. An iron atom has four electrons whose spins are unpaired, and in solid iron a quantum effect called the exchange interaction makes neighbouring atoms line their spins up in the same direction. Groups of a few billion atoms pointing the same way form a domain. A fresh iron nail is full of domains pointing in every direction, so their fields cancel and the nail is not a magnet, but bring a magnet near and the domains swing to line up with it, which turns the nail into a temporary magnet and pulls it in. Materials that behave this way are called ferromagnetic: iron, nickel, cobalt, and a few rare-earth metals such as neodymium.
Poles Always Come in Pairs
Field lines leave a magnet's north pole, loop around, and re-enter at the south, and cutting the magnet in half simply gives two shorter magnets with the same loops, because no experiment has ever found an isolated north or south pole, a magnetic monopole, even though physicists have looked hard for one in cosmic rays, in moon rocks, and in the debris of particle accelerators. Opposite poles attract and like poles repel, and the force grows fast as magnets get closer: halve the distance between two small magnets and the pull grows roughly sixteen times.
The Planet-Sized Magnet
Earth's outer core is liquid iron and nickel, hotter than the surface of the Sun, and it churns as heat escapes from the centre. Moving liquid metal carries electric currents, and those currents make a magnetic field that reaches thousands of kilometres into space; scientists call the whole engine a geodynamo. A compass works because its needle is a magnet that lines up with that field, and here is the twist your teacher may not mention: the needle's north end points toward Earth's geographic north because that region is, magnetically, a south pole. The field also flips every few hundred thousand years, and rocks on the sea floor keep a record of every reversal.
Electricity and Magnetism Are One Thing
In 1820 Hans Christian Oersted noticed a compass needle twitch whenever he switched on a nearby electric current, the first proof that electricity makes magnetism. That twitch changed physics. Eleven years later Michael Faraday showed the reverse: move a magnet through a coil of wire and a current flows. Those two discoveries run the modern world, because every electric motor uses current to make a magnetic field that pushes on other magnets, and every generator, from a bicycle dynamo to a power station, spins magnets past coils to make current.
Think About It
If a magnet's pull comes from lined-up electrons, what happens to the field of a bar magnet when you heat it past its Curie point, and why might a compass on Mars, a planet with no global field today, point in no useful direction at all?
A Quantum Effect You Can Hold
The magnet on your refrigerator is a piece of macroscopic quantum mechanics. Classical physics cannot produce it at all: the Bohr–van Leeuwen theorem shows that a collection of charged particles obeying Newton's laws and Maxwell's equations has, in thermal equilibrium, no net magnetization whatsoever. Permanent magnetism exists because electrons carry an intrinsic magnetic moment, spin, of roughly one Bohr magneton, and because in a few solids a purely quantum interaction lines those moments up.
From Electron Spin to Domains
Each electron's spin makes it a tiny dipole, and in a filled atomic shell the spins pair off and cancel. Iron, with its partly filled 3d shell, is left with four unpaired electrons per atom, cobalt with three and nickel with two, so each atom carries a net moment. What turns a crowd of atomic moments into a magnet is the exchange interaction, worked out by Heisenberg in 1928: because electrons are indistinguishable fermions, the energy of two neighbouring atoms depends on whether their spins are parallel or antiparallel, and in iron, cobalt and nickel the parallel arrangement wins. The effect is electrostatic in origin and enormously stronger than the direct magnetic force between the moments, which is why it can hold spins aligned against thermal agitation up to the Curie temperature, 1043 K for iron.
No Monopoles
Maxwell's equations contain the rule directly: the divergence of the magnetic field is zero everywhere, so field lines close on themselves and every north pole is the far end of a south pole. Halving a bar magnet halves the dipole rather than isolating a pole. Dirac showed in 1931 that a single monopole anywhere in the universe would explain why electric charge comes in fixed units, which is one reason the searches continue, but none has been found.
The Lorentz force explains why a magnet does nothing to a stationary charge and everything to a current: the force is perpendicular to both the velocity and the field, which is why charged particles spiral along field lines and why a current-carrying wire is pushed sideways in a motor. A dipole's field falls as the inverse cube of distance, so the force between two small magnets falls roughly as the inverse fourth power, which is why a fridge magnet holds firmly at contact and does nothing a hand's width away.
Currents Make Fields, Changing Fields Make Currents
Oersted's 1820 compass deflection showed that a current produces a field; Ampère quantified it within months, and Faraday's 1831 induction experiments showed that a changing magnetic flux drives a current. Maxwell's 1865 synthesis made the two sides of one field, and in Einstein's 1905 relativity paper the electric and magnetic fields become components of a single object that different observers split differently: the magnetism of a current is, in part, what the electrostatics of moving charges looks like from the laboratory frame.
Magnets in Living Things
Several animals sense the field. Magnetotactic bacteria grow chains of magnetite crystals that turn the whole cell into a compass needle. Loggerhead turtle hatchlings inherit a magnetic map that steers them around the North Atlantic gyre, and salmon and some birds appear to use both a magnetite-based sense and, in birds, a light-dependent chemical compass in the retina involving the protein cryptochrome. The human record is empty so far.
What Is Still Unknown
Why exchange favours parallel spins in iron but antiparallel spins in chromium can be computed but not simply explained; the details of the geodynamo's reversals remain an open modelling problem; and whether magnetic monopoles exist is a question experiments have narrowed without closing.
Why Your Kid Asked
Because a magnet is the one invisible force a child can hold in their hand and test, and because the usual answer ("it attracts metal") is wrong on both counts: it attracts almost no metals, and the real reason is one of the few places quantum mechanics shows up on a refrigerator door.
The Short Version
Magnetism comes from moving electric charge, and in permanent magnets the moving charge is electron spin. In most materials the spins pair off and cancel; in iron, nickel, cobalt and a few rare-earth alloys a quantum effect called exchange lines neighbouring spins up into domains, and magnetizing a piece means aligning the domains, so poles always come in pairs, opposite poles attract, and the force falls off steeply with distance. Earth's field comes from currents in its liquid iron outer core, not from a buried magnet, and a compass needle's north end points north because that end of the planet is, magnetically, a south pole.
The Numbers
Earth's surface field is about 50 microtesla, a fridge magnet roughly a hundred times that, a neodymium magnet over a tesla, a clinical MRI 1.5 to 3 tesla, and the strongest continuous laboratory field about 45 tesla. Iron loses its magnetism above 770 °C, its Curie point; nickel gives up at 358 °C. The compass reached Chinese navigation by the eleventh century, Oersted linked current to magnetism in 1820, Faraday found induction in 1831, and neodymium magnets arrived in 1984.
Two Common Misconceptions Worth Correcting
First, "magnets attract metal": they attract iron, nickel, cobalt and their alloys. A steel spoon may stick. An aluminum can never will, and the fridge test with a handful of coins settles it in a minute. Second, "a compass points at Earth's north magnetic pole": it points at the magnetic south pole of the planet, which sits near geographic north, a naming accident that is worth explaining once and then enjoying.
When to Pay Attention
Small, strong magnets are the real hazard. If a child swallows two or more (or a magnet and a piece of steel), they can attract each other across loops of intestine and cause a perforation; that is an emergency room visit, not a wait-and-see. Keep magnetic toys and the ball-bearing style desk magnets away from children under about six, and keep any strong magnet away from pacemakers and other implanted devices.
Something to Do Together
Make a compass: stroke a sewing needle thirty times in one direction with a fridge magnet, push it through a slice of cork, and float it in a bowl of water away from anything steel; it will settle north to south, and a second magnet brought near will swing it. Then build an electromagnet with a large iron nail, a metre of insulated wire wound tightly along it, and a fresh D battery: it lifts paper clips only while connected, and it warms quickly, so disconnect after a few seconds. The first shows a permanent magnet; the second shows that a current is one too.
Sources
- Feynman, R.P., Leighton, R.B. and Sands, M. The Feynman Lectures on Physics, Vol. II, chapters 34, 36 and 37 (The Magnetism of Matter; Ferromagnetism). Addison-Wesley, 1964.
- Griffiths, D.J. Introduction to Electrodynamics, 4th ed., chapter 6 (Magnetic Fields in Matter). Pearson, 2013.
- Kittel, C. Introduction to Solid State Physics, 8th ed., chapter 12 (Ferromagnetism and Antiferromagnetism). Wiley, 2005.
- Heisenberg, W. "Zur Theorie des Ferromagnetismus." Zeitschrift für Physik 49 (1928): 619–636.
- Dirac, P.A.M. "Quantised singularities in the electromagnetic field." Proceedings of the Royal Society A 133 (1931): 60–72.
- Faraday, M. "Experimental researches in electricity." Philosophical Transactions of the Royal Society 122 (1832): 125–162.
- Sagawa, M., Fujimura, S., Togawa, N., Yamamoto, H. and Matsuura, Y. "New material for permanent magnets on a base of Nd and Fe." Journal of Applied Physics 55 (1984): 2083–2087.
- Lohmann, K.J., Lohmann, C.M.F. and Putman, N.F. "Magnetic maps in animals: nature's GPS." Journal of Experimental Biology 210 (2007): 3697–3705.
- Needham, J. Science and Civilisation in China, Vol. 4, Part 1: Physics (the magnetic compass). Cambridge University Press, 1962.
- NOAA National Centers for Environmental Information. "Geomagnetism Frequently Asked Questions." ncei.noaa.gov.