IOP Institute of Physics

# Experiments

Forces and magnets: Magnet Magic

Powerpoint Slide 1 should be showing as the class enters.

1. Demonstration - hovering butterfly

Aims/Facts

• To catch the children’s attention and find out what they know.
 Activity Discussion View apparatus listStart with the box facing away from the class. Once the class is settled, turn the box round holding the butterfly loosely. When released, the butterfly will hover.View Safety Notes: about neodymium magnets. Ask what stops the butterfly falling down. Once they realise that there is a magnet on the top of the box, ask whether a real butterfly stay hovering in this way. Ask what is special about the butterfly in the demonstration. They will point out that the feelers are metal. (You might like to point out that there are very tiny magnets at the ends of the feelers making it look like a real butterfly.) They may notice that the butterfly is very light so that the force due to the magnet can hold the butterfly up.The next activity will help to find out more about what the feelers are made of.

2. Class activity

Aims/Facts

• Iron and steel are the common magnetic materials.
 Activity Discussion Hand out a magnet and a selection of objects made of various materials to each group.View apparatus listAsk the children, in groups of about four, to find out which objects are attracted by the magnets. They should also test other objects around them.For older groups, it might be appropriate to give them sheets to complete. Alternatively their findings can be discussed and, if there is an interactive white board, the table in Powerpoint Slide 2 could be completed.View Safety Notes. The objects that are handed round should be checked that they do not have sharp edges or places where the children can trap fingers. After the children have worked in groups for a few minutes, ask which objects are attracted by (or hang onto) the magnet.Discuss whether it is the shape or the material that determines whether the magnet attracts an object.If they decide that magnets attract metals then help them to notice that the copper and brass objects are not attracted. Help them to conclude that only the iron and steel objects are attracted. (Only mention cobalt and nickel if this seems appropriate.)Link back to the butterfly demonstration and point out the feelers are made of iron.

3. Show Powerpoint Slide 3

Aims/Facts

• The ends of the bar magnets are called the poles of the magnet.
 Activity Discussion Explain that the ends of bar magnets attract objects made from magnetic materials. These are called poles. Ask which parts of the magnets attract the objects.

4. Discussion about magnetic forces (Show Powerpoint Slide 4)

Aims/Facts

• Magnets exert forces.
• The forces can be represented by arrows.
 Activity Discussion Explain that the forces can be represented by arrows. Through discussion explain that an arrow shows direction and its length represents the size of the force. Discuss what is happening as the magnets attract the objects. They may say that the magnet pulls the iron towards it. Encourage them to link magnets with forces. They should notice that the magnet can be turned round and both ends attract the iron and steel objects.Collect in the selection of objects.

5. Class activity

Aims/Facts

• There are two sorts of magnetic poles.
• Unlike poles attract.
• Like poles repel.
 Activity Discussion Hand out a second magnet per group and ask them to place the magnets together in different ways (Show Powerpoint Slide 5).View apparatus list They should find that in some positions the magnets repel each other.Make sure they understand the word repel.There must be two sorts of poles.Collect in the magnets

6. Demonstration

Discussion

Aims/Facts
The Earth is a huge magnet.

A magnetic compass uses a magnet that can swing freely.

 Activity Discussion Hang a magnet by a fine thread and allow it to settle. Disturb the magnet and it will settle to point in the same direction. Repeat.View apparatus listShow Powerpoint Slide 6Explain that the magnet is being attracted because the Earth is like a huge magnet.The end of the magnet which points to the Earth’s North Pole is called the north seeking pole.Show Powerpoint Slides 7, 8, 9 Ask what they notice.Ask them to think out possible reasons why the magnet always points in the same direction.Ask them what people use to find their direction. Explain that a magnetic compass is a magnet that can swing round freely. (Some children might know that magnetic and true North are different.)A plotting compass is a tiny magnetic compass.Note: homing pigeons can find their way using the Earth as a magnet.

7. Demonstration

Aims/Facts

• Magnets produce forces across empty space.
 Activity Discussion Place a strong bar magnet on an OHP. Sprinkle paperclips or dressmakers’ pins over it. They will cling to the poles. Then scatter plotting compasses around the magnet. They should all be deflected.View apparatus listView Safety Notes Ask the children what causes the pins to jump to the ends of the magnet. They should say that the poles attract the pins strongly.Ask what they notice when the compasses are placed near the magnets. Encourage discussions about the magnets not needing to touch the compasses to deflect them.

8. Discussion

Aims/Facts

• Clear any confusion between the force of gravity and the force due to a magnet.
 Activity Discussion The Earth’s force of gravity and the force due the Earth’s magnetism. Ask for other examples of forces that act on things they do not touch. Get them to suggest gravity. Agree and ask in what way gravity is different. They should say that gravity only pulls but pulls everything while magnets pull and push but only on magnetic materials or other magnets.

9. Show Powerpoint Slides 11, 12, 13

Aims/Facts

• Magnets have a north and a south pole.
• Unlike poles attract.
• Like poles repel.
 Activity Discussion Use these slides to reinforce the facts about magnets.

10. Game A (Show Powerpoint Slide 14)

Aims/Facts

• Reinforce that magnetic forces act at a distance.
 Activity Discussion View apparatus listEach group should select one child who will act a seeker. This child should cover its eyes and the others should hide the magnet in a box or in the foil.When ready the seeker should use the compass to find the magnet.View Safety Notes: The boxes should be checked that they do not have sharp edges or places where the children can trap fingers. Let them play the game and discuss this in their groups for a while. Then ask what is happening and ask groups to explain.They should find that they can locate the magnets easily and find where the north and south ends are.The cooking foil is important to reinforce that not all metals are magnetic.Note: The pointed ends of the compass needles are the north poles (when made but are sometimes reversed in use).Collect boxes

11. Game B

Aims/Facts

• Reinforce that iron and steel are the common magnetic materials.
 Activity Discussion View apparatus listRepeat the game with all the boxes made of magnetic material. The seeker will be unable to find the magnet because the compass is attracted to all of the boxes.View Safety Notes. The boxes should be checked that they do not have sharp edges or places where the children can trap fingers. Ask why they cannot find the magnet. Ask what is different.Encourage the children to discuss what they have learned and ask questions. Use the discussion to revise and reinforce.

12. Computer memory game

Aims/Facts

• Magnets have lots of uses. Even in computers.
 Activity Discussion Ask one child to arrange magnets in the slots in a box.View apparatus listCover the row of magnets with black paper or a cloth so that they are hidden and ask a second child to use a plotting compass to ‘read off’ the code.Show Powerpoint Slide 15.Take this opportunity to summarise what they have learned.Show Powerpoint Slide 16. Explain that computers use tiny magnets to store memory.Discuss how a pattern can send a message.Let them devise a way of doing this. Suggest that north is yes and south is no. So when the code is read the answers to questions are given.Tell that soon there will be very new magnetic computer memory called MRAM. Computers with this will stay running even when you switch off – so time to start up will not be needed.

13. Demonstration ( Show Powerpoint Slide 17.)

Aims/Facts

• There is a lot more to learn about magnets than pushes and pulls. Magnets can be used in lots of ways.
 Activity Discussion View apparatus listDrop the block of metal down the copper pipe. Repeat and ask the class to say ‘now’ when they expect it to fall out of the bottom.Repeat with the neodymium magnet ensuring that it falls on a soft pad. This will take much longer to fall.View Safety Notes: about neodymium magnets. Explain that magnets cause lots of interesting effects.There is no need to explain why the magnet drops so slowly (eddy currents) but point out that it is because the magnet is moving. (It is used as a magnetic brake.)This links magnets and movement.

14. Demonstration – electromagnet

Aims/Facts

• A magnet can be made when an electric current flows.
 Activity Discussion View apparatus listPlace the nail and the wire on the OHP and place plotting compasses near to them to show that they are not magnetised.Wrap the wire round the nail and place back on the OHP with plotting compasses around it. Complete the circuit and the compasses will swing round.View Safety Notes: about neodymium magnets. Ask what is causing the plotting compasses to swing round.Show the compasses are pointing to the ends of the nail.Break the circuit and the compasses will swing back.When they suggest that the nail is magnetised, ask how else this might be tested. Get them to think of objects being attracted.Discuss what the objects should be made of. Then pile paperclips on the OHP and show that the nail will lift them.Explain that when they learn more about science (physics) they will learn that electric currents and magnets are closely linked.

15. Demonstration ‘kick’ (could be omitted)

Aims/Facts

• Magnets and electric currents can cause movement.
 Activity Discussion View apparatus listWhen the hanging wire is connected in a circuit connected near a neodymium magnet it moves suddenly.View Safety Notes: Wire may become hot. Connect the circuit then disconnect it. Ask what they see.Try it without the magnet so they understand that the wire only swings at the moment the circuit is connected when the magnet is close to the wire. It drops back when the circuit is disconnected.(Magnets, electric currents and movement have now been linked. They may guess that electric currents are involved in activity 12.)

16. Demonstration – Motor

Aims/Facts

• Motors use the fact that magnets and electric currents can cause movement.
 Activity Discussion View apparatus listSet up the apparatus as shown in the apparatus list in a position that can be seen by the whole class. Put the wire in place and it will begin to rotate.Show Powerpoint Slide 18.View Safety Notes: about neodymium magnets - also wire may become hot. This can be built up dramatically. When the wire spins the children are very impressed because they do not expect it to happen.

17. Discuss uses of motors.

Aims/Facts

• Physics is being used to develop better and better things used in our everyday lives.
• There is lots and lots more to learn about science.
 Activity Discussion After they have thought out some everyday things with motors in them show Show Powerpoint Slide 19.Lead into the idea that tinier and tinier motors are being developed show Show Powerpoint Slide 20.View Safety Notes: about neodymium magnets - also wire may become hot. Ask the children for examples of things that move when an electric current is switched on.Encourage them to think of examples of motorised toys, CD players etc.Discuss what the motor does in each case. (They might suggest motor cars - explain that the engine in a car is different but that modern cars have electric motors that wind windows up and down etc.)

18. Demonstration – robot

Aims/Facts

• Scientists do amazing things!
• Physics is in everything.
 Activity Discussion View apparatus listShow motorised toys or a robot toy which has several tiny motors in it.View Safety Notes: about motorised toys.Another example could be to switch on an electronic camera to show the lens move out. Discuss and point out that developments are being made continuously.Very tiny motors have been developed recently that are so small that they cannot be seen with our eyes!Show Powerpoint Slide 21.