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3. Electromagnetism : Magnetic?
Which of the metals below are magnetic metals?
Gold (Au)
Cobalt (Co)
Iron (Fe)
Nickel (Ni)
Zinc(Zn)
Copper (Cu)
Aluminium(Al)
Magnesium (Mg)
Silver (Ag)

4. Electromagnetism : Magnetic?
Only Iron [Fe], Nickel [Ni] and Cobalt [Co] are :
N S Co Ni Fe Al Zn Ag Cu Au Mg

5. What is a magnetic field ?
The region around a magnet where it has a magnetic effect is called its magnetic field.
If you put a magnetic material in that field it will experience a force. N S
The iron filings locate the magnetic field and show the direction of the forces in this region.

6. Electromagnetism :Magnetic Fields
 What does the magnetic field around a bar magnet look like ? [shape and direction].
N S
Strongest at poles
Weaker further away

7. Magnetic Fields - Experiments
Put the north poles of two bar magnets together. What happens?
Now put the two magnets under a piece of paper with the N poles together.
Carefully scatter iron filings on the paper.
Draw what you see.

8. Notice the pattern of lines of
Magnetic field pattern with N poles together S N N S
Notice the pattern of lines of
force in this region.

9. Magnetic Fields - Experiments
Put the north and south poles of two bar magnets together. What happens?
Now put the two magnets under a piece of paper with N and S poles together.
Carefully scatter iron filings on the paper.
Draw what you see.

10. Magnetic field pattern with N and S poles together
Notice the pattern of lines of force in this region.
How are they different from before?

11. Magnetic Fields - Summary
1. When two like poles (e.g. two North poles or 2 South poles) are put together, they repel each other.
2. When two unlike poles (e.g. a North and a South pole) are put together, they attract each other.
3. Scattering iron filings around the bar magnets allows us to see the lines of force of the magnetic field.

12. Making a magnet
It is possible to make a magnet by magnetising a material which can be attracted to a magnet, e.g. a paperclip. This can be done by:
Stroking a magnet along the paperclip from one end to the other and then starting from the same place, repeat the movement. The more times this is done, the more magnetic the clip becomes.
Holding a nail in a magnetic field and hitting it with a hammer.
Putting a magnetic material in strong magnetic field.

13. Electromagnetism : Magnetic Fields
 What does the magnetic field around a current carrying wire look like?
 Remember the ‘screw’ rule:
Current (I)

14. Record your results in the tables following:
Electromagnetism : Magnetic Fields
 What does the magnetic field around a current carrying coil [solenoid] look like?
Using an iron nail as a solenoid investigate the properties of the magnetic field.
Keeping the current the same, investigate how many paper clips the solenoid will support as the number of coils is varied.
Then, keeping the number of coils of wire the same, investigate how many paper clips the solenoid will support as the current is varied.
Record your results in the tables following:

15. Electromagnets Animation

16. Remember - keep the current the same!
Electromagnetism : Electromagnets
Remember - keep the current the same!

17. Remember - keep the number of coils the same!
Electromagnetism : Electromagnets
Remember - keep the number of coils the same!

18. Electromagnetism : Electromagnets

19. Electromagnetism : Electromagnets

20. Electromagnetism : Electromagnets
We use large electromagnets in scrap yards to pick up scrap metal:
What metals would the electromagnet attract?
What advantages does an electromagnet have over a permanent magnet?

21. Electromagnetism : Electromagnets
Door bells use electromagnets:

22. Electromagnetism : Electromagnets
Lifts, cars and other large electrical machines use high currents.
A relay can be used to allow a small current in one circuit to control a large current in another circuit.