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Making Magnets
The following are methods used to make magnets.
a) Magnetic induction – this is a process by which magnets are made by placing ferromagnetic materials in a magnetic field. Materials like iron lose their magnetism easily and are said to be soft while others like steel gain magnetism slowly but retain it longer and are therefore said to be hard and are used to make permanent magnets.
b) Magnetizing by stroking – the object to be magnetized is placed on a bench then a bar magnet is strokedalong the length of the bar from one end to the other.
This is repeated several times and the object becomes magnetized. This method is known as single-stroke method.
c) Magnetizing using an electric current – this is the use of magnetic effect of an electric current through a solenoid (insulated wire of many turns).
Demagnetizing
Demagnetizing is the process of removing magnetic properties of a magnet .
Demagnetization can be caused by;
- a) Hammering them hard with their poles facing East-West direction
- b) subjecting magnets to very strong heat
- c) Placing a magnet inside a solenoid and passing an a.c. current through it for a short time.
·Caring for magnets
- a) Magnets should be stored in pairs with unlike poles adjacent to each other attached to pieces of soft iron called keepers.
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- b) Magnets should not be hammered especially with their poles facing E-W direction.
- c) Magnets should not be heated strongly or dropped roughly on hard surfaces.
- d) Magnets should not be placed near alternating currents.
- e) Magnets should be kept dry and clean since rust can make them lose their magnetism.
Uses of magnets
- Used in making other magnets
- Used in making loud speakers
- Used in making moving coil meters
- Used in making telephone speakers.
Domain Theory of Magnetism.
Domain theory of magnetism explains how magnets are formed from small atomic ferromagnetic substance to form large groups called domains.
These substances usually exist in a haphazardly disarranged manner , often facing different direction in unmagnetized ferromagnet hence their resultant magnetism is zero.
However, when placed in a magnetic field the atomic magnets undergo rotation and eventually all domains face the same direction causing the material to become magnetized. When a material is magnetized we say it is saturated.