Fun with Magnets

• Discovery of Magnets

  • Magnes (Ancient Greek shepherd story)
  • Natural rock: Lodestone (contains iron)
  • Attraction of iron pieces

• Types of Materials

  • Magnetic Materials
    • Attracted by magnets
    • Examples: Iron, Nickel, Cobalt
  • Non-Magnetic Materials
    • Not attracted by magnets
    • Examples: Wood, Plastic, Paper, Rubber

• Poles of a Magnet

  • Magnetic Poles: Regions where attractive power is maximum
  • Two Poles:
    • North Pole (N)
    • South Pole (S)
  • Poles always exist in pairs (cannot be isolated)

• Finding Directions

  • Ancient use: South-pointing chariot (China)
  • Bar Magnet freely suspended
    • Always points in North-South direction
  • Magnetic Compass
    • Instrument to find directions
    • Uses a magnetized needle

• Making Your Own Magnet

  • Rubbing Method
    • Take an iron piece
    • Rub it repeatedly with one pole of a bar magnet
    • Always move in the same direction
  • Takes about 30-40 times to magnetize

• Attraction and Repulsion

  • Like poles (N-N, S-S) repel each other
  • Unlike poles (N-S, S-N) attract each other
  • Test for Magnetism: Repulsion is the sure test

• Care and Handling of Magnets

  • Do not heat, hammer, or drop from height
  • Keep away from cassettes, mobiles, television, computer
  • Store with keepers (soft iron pieces) and wooden blocks
  • Bar magnets stored in pairs with unlike poles on the same side