1. Magnetism

2. Magnets have been known for centuries
Magnets have been known for centuries. The Chinese and Greeks knew about the “magical” properties of magnets. The ancient Greeks used a stone substance called “magnetite.” They discovered that the stone always pointed in the same direction. Later, stones of magnetite called “lodestones” were used in navigation.

3. What is Magnetism?
Magnetism is the attraction of a magnet for another object

4. Magnets A magnet will pull some metals towards itself.
Metals that contain iron, nickel, and cobalt are magnetic. In other words, a magnet will pull them.
Magnets are made of iron, nickel, or cobalt

5. The ends of a magnet are where the magnetic effect is the strongest
The ends of a magnet are where the magnetic effect is the strongest. These are called “poles.” Each magnet has
2 poles – 1 north, 1 south.

6. For Every North, There is a South
Every magnet has at least one north pole and one south pole.  By convention, we say that the magnetic field lines leave the North end of a magnet and enter the South end of a magnet. 
If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole.  If you take one of those pieces and break it into two, each of the smaller pieces will have a North pole and a South pole.  No matter how small the pieces of the magnet become, each piece will have a North pole and a South pole.  S N S N S N

7. Breaking Magnets

8. How to break a magnet: Heat it Drop it Strike it hard
This causes the domains to become random again!

9. Every magnet has a north pole and a south pole.

10. Like repels like
Opposites attract

11. The region where the magnetic forces
Magnetic Fields
The region where the magnetic forces
act is called the “magnetic field”

12. Magnetic Field
Every magnet has a magnetic field around it. It can be thought of as a line of force running from the north end of the magnet to the south end of a magnet.
Earth’s magnetic field is what causes the needle of a compass to point north and south.

13. Magnetic Domain Atoms themselves have magnetic properties due
to the spin of the atom’s electrons.
Groups of atoms join so that their magnetic fields
are all going in the same direction
These areas of atoms are called “domains”
The entire domain acts like a magnet with a north
and a south pole

14. When an unmagnetized substance is placed in a magnetic
field, the substance can become magnetized.
This happens when the spinning electrons line up in the
same direction.

15. An unmagnetized substance looks like this…

16. While a magnetized substance
Looks like this…

17. Magnetic Domains
Magnetic force lines.

19. What do you know of that has a North and South Pole?
The Earth is one giant magnet. It has two magnetic poles and is surrounded by a magnetic field.
This magnetic field is what causes the needle of a compass to point in different directions and causes the poles of a magnet to point either north or south.

20. William Gilbert, an English physician, first proposed in 1600 that the earth itself is a magnet, and he predicted that the Earth would be found to have magnetic poles.

21. Like many Planets in our Solar System the Earth has a Magnetic Field

22. The Earth acts like a magnet
It exerts magnetic forces and is surrounded by a
magnetic field that is strongest near the
North and South
magnetic poles
Magnetic South Pole
Geographic North Pole
Magnetic North Pole
Geographic South Pole

24. The Earth behaves as if there was a magnet in its interior.

25. The North Pole of the Earth has a “south” polarity

26. As a result a compass will always point towards the North

27. A compass is a Magnetized piece of metal that can spin.

28. A compass is a Magnetized piece of metal that can spin.
North attracts South S
The north tip of the compass always points towards the North Pole of the Earth N

29. A Magnetic Field also protects us from the Solar Wind

30. The Sun produces a stream of charged particles that spread throughout the solar system.

31. These particles are deflected by the Earth’s Magnetic Field

32. The Earth’s magnetic field extends far into space
The Earth’s magnetic field extends far into space. It is called the “magnetosphere.”
When the magnetic particles from the sun, called “solar wind”, strike this magnetosphere, we see a phenomenon called…

33. The Aurora Borealis in the Northern Hemisphere
And the Aurora Australis in the Southern Hemisphere
Video Here

34. Magnetic Declination

35. Electromagnets
An electromagnet can be used to move large quantities of metal. When the current is on the magnet will pick up the metal. When you want to drop it you turn off the power and the electromagnet is disabled and the metal drops.

36. Electromagnet
A temporary magnet made by passing electric current through a wire coiled around an iron bar.
A junkyard is one place to see an electromagnet in action. A crane holding a huge electromagnet can be used to pick up scrap metal when current flows through it. When the crane operator wants to drop the scrap, he or she will simply shut off the current to the electromagnet.

37. In an electromagnet the electrons move around an iron nail+ -

38. Magnets and electricity
Magnets are used to generate, or produce, electricity.
Spinning a coil of wire inside a magnetic field produces an electric force between the ends of the coil.
In a similar way, an electric current produces a magnetic field around it.

39. Electromagnets
An electromagnet consists of an iron core placed inside a wire coil. The magnetic field strength of a wire coil carrying an electric current increases in direct proportion to the number of turns of the coil.

40. Electric Motors
An electric motor uses the sideways push of a magnetic field to turn a current-carrying wire loop. Electric motors use a commutator to change the direction of the current in the loop. Alternating current electric motors do not use commutators.

41. Oersted’s Experiment
Hans Christian Oersted discovered in 1820 that an electric current near a compass causes the compass needle to be deflected. Oersted's experiment showed that every electric current has a magnetic field surrounding it.

42. Uses of magnets
Magnets were first put to use in navigation because they always point north and south.
Magnets are used to hold, separate, control, convey and elevate products and to convert electrical energy into mechanical energy or convert mechanical energy into electrical energy.

43. Magnet Activity

44. We use magnets in many ways!
Which of the following items in a home use a magnet?
Blender washer dryer
Radio can opener dishwasher
Refrigerator doorbell compass
Click here to find out! (select kitchen on the left of the screen, close window to return to this presentation)
Magnet Activity

45. Magnets around the House:
Headphones Refrigerator magnets Computer speakers Telephone receivers Phone ringers Microwave tubes Seal around refrigerator door
Plug-in battery eliminators Floppy disk recording and reading head Audio tape recording and playback head Video tape recording and playback head Credit card magnetic strip TV deflection coil Computer monitor Computer hard drive Shower curtain weights / attach to tub Power supply transformers

46. Magnets inside of motors:
CD and DVD spinner and head positioner
Audio and VHS tape transport
VHS tape loader Microwave stirring fans
Kitchen exhaust fans Garbage disposal motor
Sump pump Furnace blower and exhaust   
Garage door opener Bathroom exhaust fan
Electric toothbrush Ceiling fan
Pager or cell phone vibrator
Clocks (not the wind-up type or LCD type)
Computers