1. P14: Electromagnetic effects
Can you write the title please (above)?

2. Let’s play!

3. Magnets
On your tables, can you write down 7 things you know about magnets

4. ALL magnets have two poles
NORTH seeking pole
SOUTH seeking pole

5. Not the same as static electricity!
Magnets are NOT charged ( + and -)

6. Breaking a magnet produces two magnets!

7. Opposites attract!

8. Opposite poles attract and like poles repel

9. Magnetic materials

10. Magnetic materials
Iron (steel), Cobalt and Nickel

11. Magnetic induction

12. Magnetic induction
When a magnetic material is close to a magnet, it becomes a magnet itself
We say it has induced magnetism
magnet S N N S

13. Hard and Soft Magnetism

14. Soft Magnetism Pure iron is a soft magnetic material
It is easy to magnetise but loses its magnetism easily
before
after N S S N N S N
Not a magnet
Iron nail

15. Hard Magnetism Steel is a hard magnetic material
It is harder to magnetise, but keeps its magnetism (it is used to make magnets!)
before
after S N S N N S N N
It’s a magnet! S
Steel paper clip

16. Gather round!

17. Magnetic field
Magnets and electric currents produce magnetic fields around them.
In a magnetic field, another magnet, a magnetic material or a moving charge will experience a magnetic force.

18. Plotting magnetic fields

19. Magnetic field lines
We can represent the magnetic field around a wire or magnet using field lines.

20. Magnetic field lines
The arrows show the direction a compass needle would point at that point in the field.

21. Can you look at the comments in your books and collect any good house marks (HP).
Do now!

22. Magnetic field lines
The arrows show the direction a compass needle would point at that point in the field.
The closer the field lines are, the stronger the magnetic force felt

23. Field around a bar magnet

24. Gather round!

25. Moving charges (currents)
Moving charges (electric currents) also produce a magnetic field
Conventional current – electrons flow in the opposite direction

26. Magnetic field around a straight wire
Current OUT of page
Current IN to page
Can you copy this?
You can use the right hand screw rule to decide which direction the field goes

27. Electromagnets

28. Field around a coil (solenoid)

29. Field around a solenoid

30. Field around a solenoid

31. Electromagnets

32. To make an electromagnet stronger?

33. To make an electromagnet stronger?
Current (A)
Mass lifted (g)

34. To make an electromagnet stronger
The 3 C’s
More Coils
More Current
Use an iron Core
Can you copy this?

37. Electric bells
Can you gat

38. Electric bells B Bell H Hammer S Screw A Armature E Electromagnet
K Switch
U Cell

39. The Electric bell
Can you stick the sheet in and complete please?

40. Relays

41. Relay circuit

42. Relay circuit
Circuit 1 is a simple electromagnet which requires only a small current. When the switch is closed, current flows and the iron rocker arm is attracted to the electromagnet. The arm rotates about the central pivot and pushes the contacts together.
Circuit 2 is now switched on. Circuit 2 may have a large current flowing through it to operate a powerful motor or very bright lights.
When the switch is opened the electromagnet releases the rocker arm and the spring moves the contacts apart. Circuit 2 is now switched off.
The advantage of using a relay is that a small current (circuit 1) can be used to switch on and off a circuit with a large current (circuit 2). This is useful for two reasons: (i) circuit 1 may contain a component such as an LDR, which only uses small currents, (ii) only the high current circuit needs to be made from thick wire.
A relay is used to operate the starter motor in cars and the heating circuit in diesel engines.

43. Relay circuit
Circuit 1 is a simple electromagnet which requires only a small current. When the switch is closed, current flows and the iron rocker arm is attracted to the electromagnet. The arm rotates about the central pivot and pushes the contacts together.
Circuit 2 is now switched on. Circuit 2 may have a large current flowing through it to operate a powerful motor or very bright lights.
When the switch is opened the electromagnet releases the rocker arm and the spring moves the contacts apart. Circuit 2 is now switched off.
The advantage of using a relay is that a small current (circuit 1) can be used to switch on and off a circuit with a large current (circuit 2). This is useful for two reasons: (i) circuit 1 may contain a component such as an LDR, which only uses small currents, (ii) only the high current circuit needs to be made from thick wire.
A relay is used to operate the starter motor in cars and the heating circuit in diesel engines.