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Rogue Physicist.  Free resources for physics education © 2006-2016 Dorian Pascoe.  Email: dorian@top-school.co.uk

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...making magnets...

 

 

 

Objectives:

 

  
 

 

 

Horseshoe magnets.

  

 

 

• Know that some magnetic materials can be turned into permanent magnets.

 

 

• Be able to describe the difference between hard and soft magnetic materials.

 

 

• Be able to explain how the alignment of domains affects the strength of a magnet.

 

  

 

 

 

 

 

 

 

 

 

Task 1 - Starter

 

  
 

 

 

Think hard!

 

  

 

 

Find someone who knows:

 

 

 

▪ What the ends of a magnet are called.

 

▪ some materials that are magnetic.

 

▪ How two magnets could be arranged to attract and/or repel.

 

 

  

 

 

 

 

 

 

 

 

 

Task 2 - Making magnets

 

  
 

 

The magnetic field around a bar magnet.

  

 

When a bar magnet is in contact with a steel nail, the nail becomes a magnet. 

 

Your teacher will demonstrate how a nail can be made into a magnet.

 

 

 

When the bar magnet is removed, the nail retains some of its magnetism.

 

 

  

 

 

 

 

Challenge

 

  
 

 

The magnetic field around a bar magnet.

  

 

• How strong can you make your magnet?

• How many paperclips can it pick up?

• How can you demagnetise your nail?

  

 

 

 

 

 

 

 

Task 3 - Sharing ideas

 

  
 

 

 

Hands up!

 

  

 

• How did you magnetise your nail?

 

• How did you make your magnet stronger?

 

• How did you demagnetise your nail?

 

• What is happening in the metal when it becomes a magnet?

 

 

 

 

Your teacher will ask you to share your ideas with the class, and may write some of them on the board.

 

  

 

 

 

 

 

 

 

Simulation - aligning domains

 

  
 

 

A bar magnet.

  

 

This simulation shows how the alignment of domains in the material affects the strength of the magnet.

 

 

 

 

Your teacher will explain this to you.

 

  

 

 

 

 

 

 

This image shows the alignment of the domains in magnetised steel.

It was taken using an electron microscope.

 

 

 

 

 

 

These images show us the domains in unmagnetised and magnetised cobalt:

 

 

 

 

 

This diagram shows the idea nicely.

 

 

 

 

 

 

 

Task 4 - Lining up domains...

 

  
 

 

 

 

 

 

 

 

 

 

 

 

  

 

Write an explanation of how:

 

 

• a piece of soft iron can be turned into a magnet.

 

• a piece of steel can be made into a permanent magnet.

 

• a piece of steel can be demagnetised.

 

 

 

 

 

Use ideas about magnetic domains in your explanation, and try to use some of the key words from the list below:

 

 

 

domains      random      field     align     soft     hard     retain     heat     impact

 

 

 

 

 

Extension:

 

Draw diagrams to show the alignment of domains in:

• An unmagnetised material

• A weakly magnetised material

• A strongly magnetised material

 

  

 

 

 

 

 

 

Lining up domains worksheet...

 

  
 

 

 

 

 

 

 

 

 

 

  

This worksheet covers the same ideas, in a different way.

 

 

 

Click here to download the worksheet.

 

  

 

 

 

 

 

 

 

 

 

 

Homework

 

  
 

 

Think hard!

A simple electromagnet.

  

 

Find out about:

 

 

 

• What is an electromagnet?

 

• How can you make a simple electromagnet?

 

• What happens to the domains in the iron core when the electromagnet is switched on?

 

• What are the uses of electromagnets?

 

 

 

 

 

Write up your ideas in your notebook, and include diagrams or pictures with your explanation.

 

  

Homework task will be available here as a word document, at some point.