1. Magnets & Magnetism

2. The discovery of magnets
In Magnesia in Ancient Greece, there lived a shepherd named Magnus One day, he was looking after his sheep in the hills.

3. The discovery of magnets
All of a sudden, he felt a mysterious force pulling his iron staff from his hand. Even the iron nails on his sandals were being pulled out.

4. The discovery of magnets
To his great surprise, he discovered that it was a huge, black rock next to him that was pulling his staff and the nails.

5. The discovery of magnets
Soon, news spread across the country about the strange rock (now called lodestone) that had the power to pull things to it.

6. The discovery of magnets
The Greeks later found other similar black rocks which had this power. These rocks were named ‘magnets’, after either Magnesia or Magnus himself.

7. Magnets Today
Magnets are one of the most important forces in our world
There is a magnet or an electromagnet inside many things

8. Magnets Today Computers store data in magnetic disks and CDs.
Electromagnets are used to lift heavy objects

9. Magnets Today Maglev trains ‘float’ on top of tracks
Doctors can see the inside of our bodies thanks to magnetic resonance imaging (MRI)

10. Magnets Today
The Earth has a magnetic field which we can use for navigation

11. What is magnetism?
Magnetism: an invisible force that pushes or pulls magnetic material.
Which materials are magnetic?

12. Magnetic Materials
Materials that are ATTRACTED TO A MAGNET, but do not attract or repel each other.
steel spoon and knife
iron nails

13. Are all metals magnetic?
cobalt (Co)
gold (Au)
iron (Fe)
nickel (Ni)
copper (Cu)
zinc (Zn)
magnesium (Mg)
aluminium (Al)
silver (Ag)

14. If you said NO you are CORRECT
cobalt (Co)
nickel (Ni)
Only iron (Fe), nickel (Ni) and cobalt (Co) are magnetic.
iron (Fe)
zinc (Zn)
magnesium (Mg)
gold (Au)
aluminium (Al)
silver (Ag)
copper (Cu)

15. Non-magnetic Materials
Materials that are not attracted to a magnet.
…metals such as gold, aluminium, silver and copper.
copper container
Aluminium
jewelry
gold jewelry

16. Non-magnetic Materials
Non-metals such as plastic, wood, paper, glass and clay are non- magnetic materials.

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

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

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

20. Sum this up
You have 5 minutes to sum up induced magnetism, soft magnetism and hard magnetism. Use the key words below to help you.
Induced magnetism, north pole, south pole, magnet, pure iron, magnetize, steel, permanent magnet, soft & hard magnetism.

21. What else should we know about magnets?

22. A magnet has 2 poles bar magnet
Poles – part of the magnet with strongest magnetic force.
The poles are called North pole and South pole
bar magnet

23. If you bring 2 bar magnets close together… Two Opposite poles attract
Law of Magnets
If you bring 2 bar magnets close together… Two Opposite poles attract

24. If you bring 2 bar magnets close together… Two Like poles Repel
Law of Magnets
If you bring 2 bar magnets close together… Two Like poles Repel

25. If you cut a magnet in half, you get…
2 smaller magnets, each with 2 poles. If you cut a magnet into many pieces, each piece is a magnet with 2 poles.

26. Taking a closer look:
Materials are made of many tiny electrons. They are always spinning around.
Domain - A group of spinning electrons.
Each domain acts as a tiny magnet.
In non-magnetic materials, the domains are pointing in all directions.

27. Domains inside magnetic materials
In magnetic materials, the domains are pointing in one direction.
The domains (tiny magnets) are working together and make the entire object magnetic.

28. Domains inside magnetic materials
In magnetic materials, the domains are pointing in one direction.

29. Domains inside magnetic materials
Domains aligned
Magnetic
Domains random
Not magnetic

30. Magnets create magnetic fields
A magnetic field is the area around a magnet where there is a magnetic force
Magnetic force is invisible, so how can we draw the magnetic field lines?

31. Magnets create magnetic fields
If you put some iron filings around a magnet, you can see the magnetic field lines.
strongest field at poles
weakest field further away from poles

32. Magnets create magnetic fields
The direction of the magnetic force is from NORTH to SOUTH

33. Magnets create magnetic fields
Two like poles repel

34. Magnets create magnetic fields
Two opposite poles attract

35. The earth has a magnetic field
Earth’s core has molten iron and nickel which is always spinning
The spinning core acts like a magnet

36. Magnetic north pole and geographic north pole are not at the same place.

37. How to plot a magnetic field
You will need to follow these instructions very carefully!
1. Put a blank piece of paper on the table in a landscape layout.

38. How to plot a magnetic field
You will need to follow these instructions very carefully!
2. Put the title of Plotting a Magnetic Field, the Date, and your name on your paper.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

39. How to plot a magnetic field
You will need to follow these instructions very carefully!
3. Place a bar magnet in the middle of the page and draw around it.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

40. How to plot a magnetic field
You will need to follow these instructions very carefully!
4. Take the magnet off and divide the rectangle in half. Colour each end.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

41. How to plot a magnetic field
You will need to follow these instructions very carefully!
5. Take a plotting compass and place it in the position shown below.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

42. How to plot a magnetic field
You will need to follow these instructions very carefully!
6. Using a pencil, put a dot on the paper where the needle is pointing.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

43. How to plot a magnetic field
You will need to follow these instructions very carefully!
7. Now place the CENTRE of the plotting compass over the dot you just made.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

44. How to plot a magnetic field
You will need to follow these instructions very carefully!
8. Now put another dot where the needle is now pointing.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

45. How to plot a magnetic field
You will need to follow these instructions very carefully!
9. Place the plotting compass over the new dot and repeat this process.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

46. How to plot a magnetic field
You will need to follow these instructions very carefully!
10. Keep going until you either go off the page or you loop back around to the other side of the magnet.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

47. How to plot a magnetic field
You will need to follow these instructions very carefully!
11. Now place the plotting compass in a new starting position. Try and ‘mirror’ the line you have just done.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

48. How to plot a magnetic field
You will need to follow these instructions very carefully!
12. Keep repeating this process completing as many lines as possible within the lesson. Try lots of different starting points.
16th Sept. 2016
Ms Holland
Plotting a magnetic field

49. How to plot a magnetic field
You will need to follow these instructions very carefully!
13. If you are successful, you should end up with a pattern like the one below.
16th Sept. 2016
Ms Holland
Plotting a magnetic field
The more lines you do, the better the diagram.