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1. Announcements • Welcome Back! • Quiz Friday. • Raffle drawing on Friday!

2. Objective • Describe the structure and properties of a magnet by drawing a magnetic field and explaining how magnets interact.

3. Magnets! • A magnet is any object that attracts certain metals, such as iron, nickel and cobalt due to its magnetic field. • A magnet can also attract or repel another magnet.

4. Magnets come in all shapes and sizes. Almost every refrigerator door has two to provide that last, snug pull when it closes.

5. Common Uses of Magnets • Magnets are found in loudspeakers, electrical motors and electrical generators. A very common application of magnets is to stick things to the refrigerator. Since the outer shell of most refrigerators is made of steel, a magnet will readily stick to it. The type of magnets used often consists of a thin sheet of a magnetic material. • Some rocks and minerals are natural magnets • Magnetite (also called Lodestone) is one example • Pieces of this rock always point north and south

8. Two Examples of Magnets Bar magnet Horseshoe magnet

9. Magnets attract IRON and STEEL

10. Magnetic Poles! • A magnet has two poles, the north pole and the south pole. • Opposite poles attract, like poles repel • When you put an N and N side together or an S and an S side together, the magnets will repel each other because they are alike • When you put an N and an S together, they will be attracted to each other because they are opposites

11. Magnetic Poles!

13. For Every North, There is a South As far as we know, every magnet has two poles. They always have both a north and a south pole! 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

14. No Monopoles Allowed It has not been shown to be possible to end up with a single North pole or a single South pole, which is a monopole ("mono" means one or single, thus one pole).  Note: Some theorists believe that magnetic monopoles may have been made in the early Universe. While monopoles may exist, none have been found. S N

15. Magnetic Fields! • A magnetic field is an invisible field of force extending out from a magnet • The magnetic field hypothetically extends out forever, but we can only feel the force of the field when we are near the magnet

18. Magnetic Field • Magnetic field lines alwaysstart at a magnets north pole and end on the south pole.

19. Magnetic Field Lines • Magnetic field lines are close together where the field is strong and get further apart as the field gets weaker. • Fields are stronger at the poles.

20. Magnetic Field for a Bar Magnet

21. Magnetic Field for a Horseshoe Magnet

22. Magnetic Force • The magnetic fields create a magnetic force. • This force explains why magnets don’t have to touch to attract or repel objects.

23. Attraction • When field lines curve towards each other it shows attraction.

24. Repulsion • Field lines that curve away from each other show repulsion.

25. Where do magnetic fields come from? • A moving electric charge, such as a moving electron, creates a magnetic field.

26. Inside every magnet are atoms with moving charges called electrons. • Not only do electrons swarm around the nucleus, they spin. • Remember, all matter is made of atoms so everything has electrons that are moving

27. In some magnets, there’s a large amount of atoms that have their magnetic fields pointing in the same direction. Are these atoms lined up?

28. Magnetic Domain • When groups of atoms have their magnetic fields pointing in the same direction, it is called a magnetic domain. • When many of the magnetic domains are pointing in the same direction, we have a magnetic object.

30. Making a Magnet • domains in which the magnetic fields of individual atoms align • orientation of the magnetic fields of the domains is random • no net magnetic field. • when an external magnetic field is applied, the magnetic fields of the individual domains line up in the direction of the external field • this causes the external magnetic field to be enhanced

31. Check for Understanding Every magnet is surrounded by a: • Magnetic domain • Magnetic Field • Superconductor • Transformer

32. Check for Understanding • Two north poles ________________, but a north and a south pole ___________.

33. Check for Understanding • Magnetic _____: surrounds a magnet and exerts a magnetic force on other objects. • Magnetic ______: group of atoms whose fields point in the same direction.

34. Check for Understanding • In which direction do magnetic fields run?

35. Check for Understanding What happens to the poles of the bar magnet if you cut it in half?

36. What type of magnetic is this? • Why do you think the steel pins are attracted to the magnet where they are? • What would the magnetic field look like?