Magnets have two poles — north and south. Like poles repel, opposites attract. Magnetic fields are inseparable from electric currents.
You snap a bar magnet cleanly in half. What do you get?
A magnetic dipole: the field loops out of N and into S. Snap a bar magnet in two and each half is a fresh dipole — you can never isolate a single pole.
Magnetism is moving charge
Every magnetic field comes from electric charge in motion — a current in a wire, or the spin of electrons inside iron atoms. That's why an electromagnet switches off when you cut the current, and why magnetism and electricity are really one force: electromagnetism.
Rules of thumb
- Like poles repel; opposite poles attract.
- Field lines run from N to S outside the magnet.
- A moving magnet near a coil makes a current — that's a generator.
- A current near a magnet feels a force — that's a motor.
Electric motors, generators, hard drives, MRI scanners, maglev trains, compasses, and the magnetosphere that shields Earth from solar wind all run on magnetism.
Cut a magnet in half — you don't get a north and a south. You get two complete magnets, each with both poles.