1. Exploring Magnets
Aseel Samaro

4. Introduction Magnets have many effects, sometimes surprisingly strong.
They have many uses including computer hard drives, loudspeakers, credit card strips, magnetic fasteners and compasses for navigation.
Even though satellite navigation is very effective, ships and aircraft still carry navigation compasses.

5. Magnetic forces Magnetism is an example of a non-contact force.
Magnets exert a force on the region around them.
A magnet will attract any magnetic materials that are close enough. They do not need to be touching to have an effect.

6. There are three magnetic elements:
iron
nickel
Cobalt
Many alloys of iron are also magnetic, including most types of steel.
Magnets have two ends, called poles. These are the north-seeking pole (N) and the south-seeking pole (S).

7. What type of force is magnetism. List four magnetic materials
What type of force is magnetism? List four magnetic materials. Name the two poles that magnets have.

8. What type of force is magnetism
What type of force is magnetism? non-contact, pushing or pulling List four magnetic materials. iron, nickel, cobalt, steel Name the two poles that magnets have. north-seeking (N); south-seeking (S)

9. Attaching and repelling
If two magnets are brought together, the effect will depend on their positions:
north to north repels
south to south repels
north to south attracts.

10. A useful way to find out whether materials are magnetised or un-magnetised is by how they behave when another magnet is brought close.
The unmagnetised material will be attracted by either pole of the magnet; the magnetised material will be either attracted or repelled, depending on the orientation of the poles.
There will be no force from a magnet on non-magnetic materials.

11. Like poles repel, unlike poles attract.

12. Describe the rules about magnets attracting and repelling each other.
Describe what will happen in each of these situations:
The N pole of a magnet is brought towards the S pole of another magnet.
The S pole of a magnet is brought towards a piece of magnetised iron.
The N pole of a magnet is brought towards a piece of copper.
Explain why a magnet hanging on a thread will respond to magnetic forces more easily than a magnet laying on a bench.

13. Describe the rules about magnets attracting and repelling each other.
like poles repel; opposite poles attract
Describe what will happen in each of these situations:
The N pole of a magnet is brought towards the S pole of another magnet. attract (not ‘stick’)
The S pole of a magnet is brought towards a piece of magnetised iron. attract
The N pole of a magnet is brought towards a piece of copper. no effect
Explain why a magnet hanging on a thread will respond to magnetic forces more easily than a magnet laying on a bench.
A hanging magnet experiences less friction than one on a bench

14. Effect of magnets
Magnets exert a force in the region around them and the effect can be detected with a magnetic compass.
Normally, a compass needle orientates itself in line with the Earth’s magnetism, but close to a magnet the force exerted is greater than the Earth’s magnetism.
As a magnet is brought towards a compass from a distance there comes a point when the needle is no longer in line with the Earth’s magnetism.
The stronger the magnet, the larger the region around it that will be affected.

15. Explain, using examples including magnetism, the differences between contact and non-contact forces. Someone states that ‘magnets stick together’. What would be a better explanation of the behaviour of magnets? Explain the similarities and differences between the Earth’s gravitational and magnetic forces.

16. Explain, using examples including magnetism, the differences between contact and non-contact forces. Contact forces act only when objects are touching e.g. a hand pushing a door, air touching a moving object. Non-contact forces can act over a distance even when there is no direct contact e.g. gravity pulling on an unsupported object Someone states that ‘magnets stick together’. What would be a better explanation of the behaviour of magnets? Two opposite magnet poles attract one another; two like magnet poles repel one another. (‘Attract’ is more appropriate than ‘stick’ because it is a non-contact force. The orientation of the poles affects whether or not they attract.) Explain the similarities and differences between the Earth’s gravitational and magnetic forces. similarities: both are non-contact forces differences: gravitational forces only attract, they cannot repel; gravitational forces act on all objects with mass, but magnetic forces only affect magnetic materials

17. Did you know…?
The Earth’s North Pole behaves as a magnetic south pole S, because it attracts the N end of a compass.
Changes in the Earth’s core mean that its magnetic poles move.
For accurate compass navigation this has to be accounted for.

18. Thank you