Definition · Plain-language
Magnetism
Magnetism is the force of attraction or repulsion produced by moving electric charges and by certain materials such as iron.
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Poles and magnetic fields
Every magnet has two poles, conventionally called north and south. The basic rule is that like poles repel and unlike poles attract, so two north poles push apart while a north and a south pole pull together. Around every magnet is a magnetic field — an invisible region where the magnetic force acts — which is strongest near the poles and can be revealed by iron filings arranging themselves into looping patterns. Unlike electric charges, magnetic poles always come in pairs: cut a magnet in half and each piece has its own north and south pole.
Where magnetism comes from
At its root, magnetism comes from the motion of electric charge. Inside magnetic materials such as iron, nickel and cobalt, the tiny currents created by spinning and orbiting electrons act like minute magnets. In most materials these point in random directions and cancel out, but in a permanent magnet large groups of them line up, producing an overall magnetic field. Heating a magnet strongly or striking it can scramble this alignment and weaken it, which is why magnets can lose their strength.
The link with electricity
Magnetism and electricity are inseparable, two faces of the single force of electromagnetism. A moving electric charge or an electric current creates a magnetic field, which is how an electromagnet works — a coil of wire becomes magnetic only while current flows. Conversely, a changing magnetic field drives an electric current, the principle of electromagnetic induction that underlies generators and transformers. This deep connection, described by Maxwell in the nineteenth century, also revealed that light itself is an electromagnetic wave.
Key facts
At a glance
- Definition: attraction or repulsion from moving charge and magnetic materials
- Poles: every magnet has a north and a south pole
- Pole rule: like poles repel, opposite poles attract
- Magnetic field: the region around a magnet where the force acts
- Source: ultimately the motion of electric charge
- Electromagnetism: magnetism and electricity are aspects of one force
Common misconceptions
What people often get wrong
Often heard: You can isolate a single magnetic pole.
Actually: Magnetic poles always come in pairs. Cut a magnet in half and you get two smaller magnets, each with its own north and south pole — an isolated single pole has never been observed.
Often heard: All metals are magnetic.
Actually: Only a few metals, mainly iron, nickel and cobalt and their alloys, are strongly magnetic. Many common metals such as aluminium, copper and gold are not attracted to magnets.
Often heard: Magnetism and electricity are completely separate forces.
Actually: They are two aspects of one force, electromagnetism. Moving charges create magnetism, and changing magnetic fields create electric currents, which is how motors, generators and transformers work.
Going deeper
