Magnetism & Electromagnetism (Years 8–11) — Science

Hold two fridge magnets close and you feel it before they touch: sometimes an invisible push, sometimes a tug pulling them together. That invisible force is magnetism, and with a little electricity you can switch it on and off at will.

Why this matters: Electric motors, doorbells, loudspeakers, scrapyard cranes and the hard drive that once stored your files all rely on magnetism and electromagnets. It is one of the most useful forces we control.

Field lines run from north to south

Poles: push and pull

Every magnet has two ends called poles: a north pole and a south pole. The golden rule is:

Like poles repel · Unlike poles attract

Like poles repel, unlike poles attract — two norths push apart; a north and a south pull together.

So two norths push apart, two souths push apart, but a north and a south pull together. Only a few metals are magnetic — the ones to remember are iron, steel, nickel and cobalt. Most metals, including copper and aluminium, are not magnetic at all.

The invisible field

Around every magnet is a magnetic field — the region where its force can be felt. We draw it as field lines that always run from the north pole to the south pole. Where the lines are close together the field is strong; where they spread out it is weak.

Field lines loop from north to south; closer lines mean a stronger field.

Analogy: field lines are like the flow of a river drawn on a map — they show which way the force pushes and how strong it is, even though you cannot see the water itself.

Electromagnets: magnetism you can control

Here is the powerful idea: an electric current flowing through a wire creates a magnetic field around it. Wrap the wire into a coil around an iron core and you build an electromagnet. Its huge advantage over an ordinary magnet is that you can switch it on and off just by switching the current — which is exactly how a scrapyard crane grabs a car, then drops it.

Current in a coil round an iron core makes an electromagnet — switch the current to turn it off.

You can make an electromagnet stronger in three ways:

More turns of wire on the coil.
More current flowing through it.
Adding an iron core inside the coil.

Feature	Ordinary magnet	Electromagnet
Can be switched off?	✗ No	✓ Yes
Strength adjustable?	✗ No	✓ Yes (turns, current, core)
Needs electricity?	No	Yes

Worked reasoning. "How would you make a doorbell electromagnet pull harder?" Ask: "what three things control its strength?" — turns, current, and core. So add more turns of wire, push more current through it, or fit an iron core. Each gives a stronger field. No new rule needed — just recall the three levers.

Common mix-up: assuming all metals are magnetic. They are not — only iron, steel, nickel and cobalt are attracted. Aluminium, copper, gold and silver are not magnetic, even though they are shiny metals.

Memory hook: No-No and S-Same poles repel; opposites attract. Field lines flow N → S. And an electromagnet is the easy magnet — you can turn it off.