P4.1 Simple Phenomena of Magnetism

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Lesson Objectives

Describe the forces between magnetic poles and between magnets and magnetic materials.
State the difference between magnetic and non-magnetic materials.
Compare temporary magnets made of soft iron with permanent magnets made of steel.
Describe how a permanent magnet differs from an electromagnet.
Describe a magnetic field and state its direction.
Describe induced magnetism.

Starter

Think about where you have seen magnets in daily life. Magnets are used in fridge doors, speakers, electric bells, compasses, motors, and scrapyard cranes.

Key idea: magnets can attract some materials and can also attract or repel other magnets.

Magnetic Poles and Forces

Magnets have two poles: North (N) and South (S).

Like poles repel.
Unlike poles attract.
Magnets also attract magnetic materials such as iron and steel.

Rule to remember: N + N repel, S + S repel, N + S attract.

Animated Magnet Interactions

N

S

N

S

Facing poles: S and N Force: Attraction

What is happening?

Unlike poles are facing each other, so the magnets pull together.

Flip the second magnet to change which pole faces the first magnet, then test attraction or repulsion again.

Magnetic and Non-Magnetic Materials

Magnetic materials	Non-magnetic materials
Iron	Plastic
Nickel	Wood
Cobalt	Glass
Steel	Rubber

Magnetic materials can be attracted by a magnet and may become magnetised.

Temporary vs Permanent Magnets

Feature	Temporary magnet	Permanent magnet
Main material	Soft iron	Steel
Magnetised easily?	Yes	Less easily
Retains magnetism?	No, loses it quickly	Yes, keeps it for longer
Common use	Electromagnets	Bar magnets and compass needles

Permanent Magnet vs Electromagnet

Permanent magnets do not need electricity.
Electromagnets need electric current to work.
Electromagnets can be switched on and off.
The strength of an electromagnet can be changed.

Animated Magnetic Field Lines

N

S

A magnetic field is a region where a magnetic pole experiences a force. Outside the magnet, field lines go from North to South.

Induced Magnetism

Induced magnetism happens when a material becomes magnetised because it is placed near a magnet or inside a magnetic field. This effect is often temporary, especially in soft iron.

Mini Practical

Place a bar magnet under a sheet of paper and sprinkle iron filings over the paper. Tap the paper gently. The filings line up in a pattern which shows the magnetic field. The field is strongest near the poles.

Quiz (20 MCQs)

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Class Summary

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