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What is Magnetism?.

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Presentation on theme: "What is Magnetism?."— Presentation transcript:

1 What is Magnetism?

2 Magnet Magnet: Any material that attracts iron and materials that contain iron. Magnetite: A magnetic material found in rocks Magnetism: The attraction or repulsion of magnetic materials.

3 3 Properties of Magnetism
1. Magnets attract iron or materials that contain iron. 2. Magnets attract or repel other magnets. 3. One part of a magnet always points north when allowed to swing freely.

4 Magnetic Poles Magnetic Poles: The ends of a magnetic object, where the magnetic effect is strongest. Magnets have a North Pole and a South Pole. Magnetic Poles that are unlike attract each other. Magnetic Poles that are alike repel each other. What happens when you bring the two side together?

5 Magnetic Force Magnetic Force: The attraction or repulsion between magnetic poles. It is produced when poles interact. Force is the push or pull on an object that makes the object move.

6 Magnetic Fields Magnetic Field: The area of magnetic force around a magnet. Magnetic Field Lines: Invisible Lines that map out the magnetic field around a magnet. Magnetic Field Lines spread out from one pole, curve around the magnet, and return to the other pole. These lines form complete loops from pole to pole and the lines NEVER cross.

7 Magnetic Fields The distance between magnetic field lines indicates the strength of the magnetic field. The closer together the lines are, the stronger the field. The field lines are closest together at the poles. How can you tell by the lines in Figure 4 where the magnet’s magnetic field is strongest?

8 Inside a magnet

9 Atoms All matter is made up of atoms
Atom: the smallest particle of an element. Element: one of the 100 basic substances that make up all matter.

10 Structure of an Atom Nucleus: the center region of an atom
The nucleus is made up of two kinds of particles, protons and neutrons. Proton: is a particle with a Positive charge. Neutron: a particle that does not carry a charge. N= NO charge Electron: a particle that carries a negative charge. Electrons move randomly through the atom and they are much smaller than protons and neutrons.

11 Electron Spin Each electron in an atom has a property called electron spin. A spinning electron produces a magnetic field that makes the electron behave like a tiny magnet in an atom. In most atoms, electrons form pairs that spin in opposite directions. When electrons spin in opposite directions, the magnetic fields are cancelled. When the electrons are NOT paired, they tend to have strong magnetic properties.

12 Magnetic Domain Magnetic domain is a group of atoms that have their magnetic fields aligned. The direction in which the domains point determines if the material is magnetized or not magnetized.

13 In a material that is NOT magnetized, the magnetic domains point in random directions.
In a material that IS magnetized, the magnetic domain points in the same direction.

14 Magnetic Materials Ferromagnetic Material is a material that shows strong magnetic properties. Read section Magnetic Materials on pg 17 and make a list of a few Ferromagnetic Materials.

15 Making and Changing Magnets
Temporary Magnet: A magnet made from a material that easily loses it’s magnetism. Permanent Magnet: A magnet made from a material that keeps it’s magnetism for a long time. If an object containing iron, such as a metal locker or filing cabinet, is left in the same place for a long period of time, the object may become magnetized. Do you think your lockers have become magnetized? Create your own magnet. Read pages 18 and 19 silently. How can we destroy a magnet? Will a magnet still work if broken into 2 pieces? Into 10 pieces?

16 Section 3 Magnetic Earth

17 Earth as a Magnet Compass: A device that has a magnetized needle that spins freely. Earth has a magnetic field surrounding it and 2 magnetic poles. A compass works by aligning itself with Earth’s magnetic field. Circulation of molten material in Earth’s core is related to Earth’s magnetism. Look at Figure 12 on Pg. 23. We can see that the magnetic poles are NOT in the same place as our geographic poles.

18 Magnetic Declination Magnetic Declination: The angle between geographic north and the north to which a compass needle points. Imagine you could draw a line from you to the geographic North Pole. Then, you drew a line from you to the magnetic pole in the Northern Hemisphere. The angle measure between these two lines is the magnetic declination.

19 Homework: Read page 25-27 Answer the following questions:
What evidence shows that Earth’s magnetic field changes? What causes an aurora? What are the Van Allen belts? What is the magnetosphere? Using a compass, determine whether or not metal objects in your home that have been in the same place for a long period of time are magnetized. Make a list of the objects you tested and explain whether or not they were magnetized. Explain to a family member why the compass needle moves away from north near the objects.

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