Magnetism

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This is my magnetism presentation.
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Magnetism

  1. 1. Magnetism http://commons.wikimedia.org/wiki/File:Bar_magnet.jpg
  2. 2. History The Greek's found a metal that always pointed in the same direction in Magnesia. They called it magnetite. http://commons.wikimedia.org/wiki/File:Magnetite-114528.jpg
  3. 3. Bar Magnets A bar magnet is a 'bar' with two poles – North and South. Like poles ________ and opposite poles ______. The attraction and repulsion causes a magnetic force. http://commons.wikimedia.org/wiki/File:Bar_magnet.jpg
  4. 4. Magnetic Fields What is a field (in real life)? What is a field in Physics? In Physics, a field is somewhere that forces act. http://upload.wikimedia.org/wikipedia/commons/b/bc/TTU_Women%27s_Soccer_Field.jpg
  5. 5. Magnetic Field Lines Field lines never cross The field lines point from north to South. The field lines show the direction a north pole would be pushed. What does the number of field lines show? ANS: the strength of the field. http://upload.wikimedia.org/wikipedia/commons/a/a8/Magnetic_field.svg
  6. 6. Magnetic Domains Atoms of iron, cobalt and nickel contain domains. A magnet is made of many domains, which all point the same way. In (non-magnetic) iron, the domains point in random ways so their effects cancel each other out. http://www.wholistichealthworks.com/images/magnetized%20domains.GIF
  7. 7. Cutting Up Magnet It is impossible to cut a magnet into each pole. If the magnet is cut in half (or other proportions), the domains still point in the same direction, so it is still a magnet. There are still north and south poles.
  8. 8. Earth as a Magnet Earth's magnetic field is caused by iron in the Earth's core. Which pole is where? http://upload.wikimedia.org/wikipedia/commons/1/17/Earths_Magnetic_Field_Confusion.svg
  9. 9. Magnetic vs True North Magnetic North and True North are different. A compass points to magnetic north. True North is the Earth's pole. Choose a country and find the difference between magnetic north and true north, known as magnetic declination. Magnetic declination is important for anyone who needs to know the precise direction of true north using a compass. http://longhamscouts.org.uk/images/stories/resources/scouts/hiking/navigation/magnetic_field.jpg
  10. 10. AURORA Charged particles (=?) leave the sun. They are attracted to the magnetic poles of the Earth. As they enter the atmosphere, chemical reactions occur which generate bright, vivid, beautiful colours. Where can an Aurora be seen? Google image: Auroras for some beautiful images!!
  11. 11. Physics Now <ul><li>Read pages 134-141
  12. 12. Answer questions (on side) 1, 2,3,` 5, 6, 7, 8, 9 (no need to do it), 10, 11, 12. </li></ul>
  13. 13. Revision Questions <ul><li>What three elements are magnetic?
  14. 14. Where is the Earth's magnetic north pole located? (where is it close to?)
  15. 15. What is meant by 'magnetic declination'? Give an example for somewhere in the world.
  16. 16. Explain why there is a magnetic north pole close to the Earth's geographic south pole.
  17. 17. Explain what causes the aurora, including why it is only visible near the Earth's poles.
  18. 18. Explain what is meant by domains. What is the difference between magnetised and non-magnetised material, in terms of domains? NEW:
  19. 19. 7. Occasionally the Earth's magnetic poles reverse, and in between there is a period in which the magnetic field of the Earth disappears. What effect would this have on life on Earth? </li></ul>
  20. 20. Revision Questions <ul><li>What three elements are magnetic?
  21. 21. Where is the Earth's magnetic north pole located? (where is it close to?)
  22. 22. What is meant by 'magnetic declination'? Give an example for somewhere in the world.
  23. 23. Explain why there is a magnetic north pole close to the Earth's geographic south pole.
  24. 24. Explain what causes the aurora, including why it is only visible near the Earth's poles.
  25. 25. Explain what is meant by domains. What is the difference between magnetised and non-magnetised material, in terms of domains? NEW:
  26. 26. 7. Occasionally the Earth's magnetic poles reverse, and in between there is a period in which the magnetic field of the Earth disappears. What effect would this have on life on Earth? </li></ul>
  27. 27. Electromagnetism <ul><li>An electric current produces a magnetic field.
  28. 28. The direction of the magnetic field is circular, around the wire.
  29. 29. A compass needle will deflect if it is close to a wire carrying electricity.
  30. 30. This principle is used by ______________. </li></ul>http://images.wikia.com/psychology/images/0/07/Electromagnetism.png

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