Demagnetizing a magnet 

Demagnetizing a magnet

  • It is making a magnet lose its magnetism.
  • It is weakening or destroying a magnet.
    Ways of demagnetizing a magnet
  • Hammering/hitting strongly.
  •  Strong heating.
  •  Leaving a magnet in an east-west direction for a very long time.
  •  By keeping the magnets with like poles together.
  •  By passing an alternating current through a magnet.
  •  Leaving it to rust.
  • Uses of magnets in modern world of work.
  • Magnets are used in compasses by sailors, pilots and explorers.
  • Electromagnets are used in industries to collect heavy scrap iron.
  • An electric bell is also built on the principle of magnets.
  • Magnets are used in telecommunication devices.
  • Electric motors which produce electricity use magnets.
  • They are used in loud speakers.
  • They are used on doors of fridges.

Appliances that use electricity

  • Flat irons
  •  Heaters
  •  Driers.
  •  Washing machines
  •  Electric fans
  • Cooker

Appliances that use magnetism

  • Magnetic compasses.
  • Magnetic tapes.
    Appliances that use both electricity and magnetism..
  • Fridges.
  •  Radios
  • Televisions
  •  Mobile phones
  •  Electric bells

An Electric bell

electric bell

How it works

  • When the contact is made the soft iron becomes magnetized.
  • It pulls the soft iron strip with the hammer.
  • The hammer hits the gong producing sound.
  • When the strip is pulled the soft iron loses its magnetism and the contact is broken because current is not flowing.

Generating electricity using a dynamo.

Dynamo.

A dynamo is a device which converts mechanical energy into electrical energy.
A dynamo uses a permanent magnet and a coil of wires on electro magnets

During the turning, the mechanical energy is turned into electric energy.

Generator

The type of current electricity produced is A.C

They change Mechanical energy to electric energy.

Uses of dynamos and generators

  • Provide electricity for light.
  • Provide energy to run machines.
  • Provide energy for cooking
  • Generators are used in hospital theatres incase power goes out.


Topical questions

  1. How is magnetism different from magnets?
  2. State the any one law of magnetism
  3. How are magnets important to the following?
  4. Doctors                               b) pilots          c) teachers
  5. Cite one item that uses both magnets and electricity.
  6. How are magnets found in radios important?
  7. In four sentences, briefly explain how an electric bell works.
  8. Write the term AC in full.
  9. What is the importance of the hammer found on an electro magnet?
  10. State one way of making magnets.
  11. In which one way can a p7 child make a magnet lose its magnetism?
  12. Briefly explain how strong heating a magnet can make it lose its magnetism?