C. Matter and Energy · Forces Causing Movement

Magnetism: Pulling Without Touching

C2.1 A1.2 A1.4About 35 minutes

Learning goals

I can explain that magnetism is a non-contact force.
I can sort objects into ones a magnet attracts and ones it does not.
I can explain that opposite poles attract and the same poles repel.
I can test how magnetic force works through materials and over a distance, and handle magnets safely.

Words to know

magnet
An object that pulls on iron and steel, and pushes or pulls on other magnets.

magnetism
The non-contact force of a magnet.

attract
To pull toward.

repel
To push away.

pole
One end of a magnet, where its force is strongest. Every magnet has a north pole (N) and a south pole (S).

magnetic
Pulled by a magnet. Iron and steel are magnetic.

compass
A tool with a magnet needle that points north. It helps people find their way.

A magic trick?

Put a paper clip on a piece of paper. Hold a magnet under the paper and move it around. The paper clip slides along on top, as if by magic!

It is not magic. It is magnetism, a force that can pull without touching.

What do magnets pull?

Magnetism is a non-contact force. A magnet can pull from a little distance away, across a gap.
Magnets attract (pull) things made of iron or steel, like a steel paper clip, an iron nail or a steel soup can. A few other metals, like nickel, are magnetic too.
Magnets do not attract most other things: wood, plastic, paper, glass, rubber, cloth. They also do not attract all metals. Aluminum (like foil and pop cans) and copper are not pulled.
Magnetic force works through some materials, like paper, thin cardboard, plastic and water.
The force is strongest up close. It gets weaker the farther away you go.

A red horseshoe magnet holding steel nails and paper clips at its ends, next to a pencil, a button, an eraser and a disc of aluminum foil. — The magnet pulls the steel nails and paper clips, which cluster at its poles. The wooden pencil, plastic button, rubber eraser and aluminum foil are not attracted. AI-generated image

Poles: north and south

Every magnet has two ends called poles: a north pole (N) and a south pole (S). The force is strongest at the poles.

Different poles attract: N and S pull together.
The same poles repel: N and N push apart. S and S push apart.

So a magnet can pull and it can also push!

Top: a south pole near a north pole. The magnets attract and pull together. Bottom: a south pole near a south pole. The magnets repel and push apart.

Earth is like a giant magnet

A compass needle is a tiny magnet. The Earth acts like a giant magnet, so the needle turns to point north. People have used compasses for a long time to find their way on land and at sea.

Worked example

Let's sort: magnetic or not?

Which of these will a magnet attract? A steel paper clip, a piece of aluminum foil, a wooden pencil, an iron nail, a plastic button, a steel soup can, an aluminum pop can.

Ask: Is it made of iron or steel?
Steel paper clip: yes. Iron nail: yes. Steel soup can: yes.
Wooden pencil and plastic button: no. They are not metal at all.
Aluminum foil and aluminum pop can: no. They are metal, but aluminum is not magnetic. Not all metals are!

Attracted: paper clip, nail, soup can. Not attracted: foil, pencil, button, pop can. Recycling centres use big magnets to pull steel cans out from the other recycling, because aluminum cans are not pulled.

A magnet pulls things made of iron or steel. Aluminum foil and pop cans are metal, but the magnet does not pull them.

Worked example

Let's test: does magnetism work through paper?

Ella put a paper clip on top of a stack of paper and held a fridge magnet under the stack. She added one sheet at a time. Her results:

1 sheet: clip moves
5 sheets: clip moves
10 sheets: clip moves a little
20 sheets: clip does not move

Magnetism went through 1, 5 and 10 sheets. So the force can work through paper.
With more sheets, the magnet is farther from the clip.
At 20 sheets the clip did not move. The force got weaker with distance until it was too weak.

Magnetism works through paper, but it gets weaker the farther away the magnet is. (A stronger magnet would work through more sheets.)

Just for fun

What did one magnet say to the other magnet?

"I find you very attractive!"

Hands-on activity

Magnet investigation

You need: a fridge magnet or a bar magnet, a steel paper clip, and a tray of small household things (a key, a coin, aluminum foil, a pencil, an eraser, a spoon, a bottle cap, a sock, a nail, a plastic toy). Also some sheets of paper and a glass of water.

Make a chart with three columns: Object, My prediction, What happened.
Predict for each object: will the magnet attract it? Then test it and record.
Look at your results. Were any metal things not attracted? Were you surprised?
Through things: drop a paper clip into a plastic cup of water. Can you pull it up the side of the cup with the magnet held outside the cup?
Distance test: like Ella, see how many sheets of paper the magnet can pull through.
If you have two bar magnets, try N to S and N to N. Feel the pull and the push.

What to look for: only some metal things are attracted (iron and steel); the magnet pulls the clip through paper, plastic and water; the force gets weaker with more paper; same poles push apart. Surprise: many Canadian coins have steel inside, so a magnet may pull them!

Safety: keep magnets away from phones, computers, screens and bank cards. Never put magnets in your mouth. Keep small magnets (and small things like coins, nails and paper clips) away from babies and pets: swallowing magnets can cause serious injury.

Your turn

Is magnetism a contact force or a non-contact force?

Will a magnet attract an iron nail?

Will a magnet attract an aluminum pop can?

What are the two poles of a magnet called?

You put the N pole of one magnet near the N pole of another. What happens?

You put N near S. What happens?

Does a magnet pull more strongly up close or far away?

More practice: warm-up

What does "attract" mean?

What does "repel" mean?

Will a magnet pick up a wooden block?

Will a magnet pick up a steel paper clip?

Which tool uses a magnet needle to point north?

More practice: on your own

Ben says "Magnets attract all metals." Is he right? Give an example.

How can a magnet move a paper clip that is on top of a table when the magnet is under the table?

Two bar magnets push apart when you bring them together. What does that tell you about the poles that are facing each other?

Why do recycling centres use big magnets?

In Ella's test, the clip moved through 10 sheets but not 20. What did she learn?

Challenge

You have a magnet whose N and S labels have rubbed off, and a second magnet with labels. How can you find out which end of the first magnet is N?

You dropped some steel pins into a sandbox. How could you get them out quickly without touching the sand with your hands? Explain.

Plan a fair test: which of two fridge magnets is stronger? Tell what you will change, keep the same, and measure.

Check your understanding

Quiz

Magnetism is...

Which will a magnet attract?

Which will a magnet not attract?

What happens when you put a north pole near a south pole?

What happens when you put a south pole near a south pole?

Where is a magnet's force strongest?

Which is a safe way to use magnets?

For parents and teachers

Big idea: Magnetism is a non-contact force (C2.1). Magnets attract iron and steel (and a few other metals such as nickel), but not aluminum, copper, plastic, wood or glass. Each magnet has a north and a south pole: opposite poles attract and like poles repel. Magnetic force passes through thin non-magnetic materials and weakens with distance. The prediction chart and the paper-sheet test practise the experimentation process (A1.2); handling magnets safely is A1.4.

How to help: Go on a magnet hunt with a fridge magnet: the fridge door, a steel can, a radiator, a pot. Ask your child to predict first. Many children are surprised that not all metal is magnetic.

Common difficulties:

"All metals are magnetic." Test aluminum foil to show otherwise.
Thinking bigger magnets are always stronger. Size doesn't always tell strength; testing does.
Mixing up attract and repel. Practise with actions: pull your hands together for "attract", push them apart for "repel".

Safety: small, powerful magnets (such as those in some building toys) can cause serious internal injury if two or more are swallowed. Store them away from young children and pets, and seek medical help right away if you suspect a magnet has been swallowed. Keep magnets away from electronics and cards.