Magnetism

•    A magnet attracts the small pieces of iron.
•    A freely suspended bar magnet, always rests in north south direction.
•    A magnet has two poles north pole and South Pole.
•    These poles exist in pair.
•    Like poles repel each other, while unlike poles attract each other.
•    A magnetic compass is a small magnetic needle pivoted at its Centre so as to rotate freely.
•    It is used to indicate the north-south direction at a place.
•    Repulsion is a sure test of a magnet.
•    The space around the magnet in which the magnetic needle of the magnetic compass gets influenced is called the magnetic field of that magnet.


                                                        

•    Electromagnet is a temporary magnet which is made up of soft iron by the electrical method.
•    An electromagnet acquires magnetism so long as current flows in the coil wound around a cylindrical tube. The strength of magnetic field of an electromagnet increases by three ways:

  1. By increasing the number of turns in the coil.
  2. By increasing the intensity of current in the coil.
  3. By inserting a soft iron core in the coil.

•    The electromagnets are mainly used:

  • To separate the iron from other substances
  • To lift big pieces of iron scrap, girders, plates etc.
  • To separate iron dust from wounds
  • To load furnace with iron
  • To obtain magnetic field in the electrical gadgets like electric bell, electric motor etc.

 

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  • Q1

    Mark the poles of the given magnet.

    Marks:1
    Answer:

    Due to the influence of earth’s magnetism, a freely suspended magnet always points in north-south direction.

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  • Q2

    Name the two important properties of a magnet.

    Marks:1
    Answer:

    The two important properties of a magnet are

    (i) Attractive property

    (ii) Directive property

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  • Q3

    What name is given to the ore of the magnet?

    Marks:1
    Answer:

    The ore of the magnet is called magnetite.

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  • Q4

    In which direction does a freely suspended magnet comes at rest?

    Marks:1
    Answer:

    A freely suspended magnet always comes at rest in north-south direction.

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  • Q5

    Which portion of a magnet shows the maximum strength?

    Marks:1
    Answer:

    The strength of a magnet is the maximum at its poles.

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