1. KS4 Electricity - Electromagnetism

2. What is a magnetic field?
Where would you find a magnetic field?

3. strongest field at poles
Magnetic field
Around every magnet is an invisible force field that will affect all magnetic objects inside it.
The magnetic field of a bar magnet is seen with iron filings.
strongest field at poles N S
What does the magnetic field around a bar magnet look like?
Where is the magnetic field strongest?

4. What materials will stick to magnets?
Look around the laboratory or your teacher will provide a tray.
See which materials will stick to a magnet and which materials will not.
Magnetic materials
Non-magnetic materials

5. What materials will magnets stick to?
Magnets and materials
What materials are magnets made from?
Iron or steel. N S
What materials will magnets stick to?
Iron or steel.
And nickel!

6. Forces between magnets – experiment

7. Repulsion and attraction
Repel/attract
Repel/attract
Repel/attract
Unlike poles attract.
Like poles repel.

8. Separating coins
How could you separate steel and gold coins using a magnet? N S
Steel coins would stick to magnet, gold coins would be left behind.

9. What does the magnetic field for a bar magnet look like?
In what direction do magnetic field lines point?
N North to South S

10. Revising magnetism I Iron or steel
Magnets are made from which materials? ___________
The Poles
What are the ends of a magnet called? __________
What do we call the area around a magnet where a
magnetic force exists? __________________
The Magnetic Field
Pull together
What does the word attract mean? __________
What does the word repel mean? __________
Push apart

11. Revising magnetism II Repel
What will two north poles do if brought together? _____
Repel
What will two south poles do if brought together? ______
Repel
What will a north and a south pole do if brought
together? _______
Attract
Iron and steel
What materials are attracted by magnets? ___________
Is magnetism a contact or non-contact force? _________
Non-contact

12. Electromagnets
A coil of wire acts like a bar magnet when it has an electric current flowing through it.
One end of the coil becomes a north-seeking pole.
One end of the coil becomes a south seeking pole.
This is called an electromagnet.

13. Making an electromagnet:
Apparatus:
Batteries
Wire
Iron Nail
What to do:
Wrap a coil of wire around the iron nail.
Connect the coil of wire to the batteries.
See how many paperclips you can pick up.

14. Results How many paperclips could you pick up?
Can you think of any ways to make the electromagnet
pick up more paperclips?
More batteries (more current)
Number of paperclips
Number of batteries
More turns of wire on the coil
Number of paperclips
Number of turns

15. Electromagnetic strength – experiment

16. Electromagnetic strength - results
The results for the number of drawing pins attracted to the electromagnet with no core are: 1 2 3 4 6 8 12 18
number
of cells
number
of coils
How does changing the current affect the strength of an electromagnet?
How does changing the number of coils affect the strength of an electromagnet?

17. Electromagnetic strength - results
Compare the results for the number of drawing pins attracted to the electromagnet with no core and an iron core: 1 2 3 4 6 8 12 18
number
of cells 1 2 3 4 6 8 10 12 16 22
number
of cells
number
of coils
number
of coils
What effect does an iron core have on the strength of an electromagnet?

18. Electromagnetic strength - results
Compare the results for the number of drawing pins attracted to the electromagnet with no core and a copper core: 1 2 3 4 6 8 12 18
number
of cells 1 2 3 4 6 8 12 18
number
of cells
number
of coils
number
of coils
What effect does a copper core have on the strength of an electromagnet?

19. Ways to make an electromagnet stronger
There are three ways to make an electromagnet stronger. Do you know them?
___________________
More turns on the coil
More electrical current
Using an iron core S S N
What happens if you turn the battery around in an electromagnet?
The poles on the coil reverse, north becomes south and south becomes north.

20.  Attract and repel Attract Repel Stick together
What do like poles do?
Attract and repel
Attract
Repel
Stick together 

21. Which material below will not stick to a magnet?
Steel paper clip
Aluminium can
Iron nail
Steel key 

22. Which of the below will not increase the strength of an electromagnet?
More coils
More current
Less current
Iron core 

23. In which direction do magnetic field lines always point?
East to west
West to east
South to north
North to south 

24. Which of the following is not a use of electromagnets?
Fridge magnets
Loud speakers
Relays
Circuit breakers 