Class 6 Science Chapter 13 Fun with Magnets, Types of Magnet, Magnetic Compass, Discovery of Magnets (For CBSE, ICSE, IAS, NET, NRA 2022)

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Fun with Magnets

Magnet

  • An object which has the ability to attract magnetic materials; like iron, cobalt and nickel is known as a magnet.
  • A magnet produces a magnetic field that attracts unlike poles and repel like poles.
  • They come in various shapes and sizes.
    • Horseshoe
    • Ring
    • Cylindrical
    • Bar shape
  • Magnetic objects are those that are attracted by a magnet for e. g. , iron and nickel.
  • Non-magnetic objects are those that are not attracted by a magnet for e. g. , wood and plastic.

Natural Magnets

  • These are found in nature like magnetite.
  • Lodestone, also called magnetite is an example of a natural magnet.

Artificial Magnets

  • These are man-made magnets made from Iron, Nickel, Cobalt.
  • Refrigerator magnets and neodymium magnets are the examples of artificial magnets.

Types of Magnets

Temporary Magnets

  • These magnets retain magnetic properties only for a short period of time.
  • These magnets are usually made of iron, cobalt, or nickel.
  • They lose their magnetic property if strong magnet is removed.

Permanent Magnets

  • These magnets retain their magnetic properties for a long period of time.
  • These magnets are made from mixtures of iron, cobalt, or nickel with other materials.

Magnet Loses Its Properties

Magnet Loses Its Properties Due to Activities

Storing a Magnet

  • Bar magnets should be kept in pairs.
  • A piece of iron across the two poles is important for storing a horse-shoe magnet.
  • Magnets should be kept away from:
    • Speakers
    • CD
    • Television
    • Music system
    • Computer, etc.

Uses of Magnets

  • A strip of magnetic material is used in Credit cards, ATM cards, and identity cards.
  • Magnets are used in television and computer monitors.
  • Magnetic material is used for storing information in Computer hard discs and audio and video cassettes.
Magnetic Compass
  • An instrument containing a magnet used for finding directions is called a magnetic compass.
  • The primary use of a magnet was to find directions in ancient times.
  • Whenever a magnet was allowed to move freely, it comes to rest in a direction very close to the Earth՚s North-South direction and this is the property used by travellers for finding directions on Earth՚s surface.
  • A magnetic compass consists of a magnetic needle which can rotate freely pointing in the Earth՚s North-South direction.
  • In fig (a) given below, the compass is rotated till the ‘north’ marking coincides with the end of the needle pointing north.
  • In fig (b) given below, the desired direction is read on the compass (north-east in this case) .
Finding Directions Using a Magnetic Compass

Poles of a Magnet

  • North pole and South pole are the two poles of a magnet.
  • At the poles of the magnet, magnetic forces are the strongest.
  • On the poles of a magnet, the magnetic power is concentrated.
  • A freely-suspended bar magnet aligns itself in north-south direction:
    • The earth acts like a huge bar magnet.
      • Magnetic North Pole facing towards geographic South Pole.
      • Magnetic South Pole facing towards geographic North Pole.
Like and Unlike Poles

Discovery of Magnets

  • Greeks used the term magnet in 600 B. C.
  • An ancient Greek shepherd named Magnes discovered Magnet.
  • It is believed that to a large black rock on which Magnes was standing the nails in his shoes and the iron tip of his stick got stuck.
  • Also, according to some people magnetite was discovered at a place called Magnesia.
  • Ancient Chinese sailors used magnets for navigation.

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