Page 150 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Methods of magnetization
• Touch method
• Single touch method
• Double touch method
• Divided touch method
• By means of electric current

• Induction method
Single touch method
The steel bar to be magnetized is rubbed with either of the pole of the magnet (N or S).Keep the other pole away
from it. Rubbing is done only in one direction. The process should be repeated for many times.
Double touch method
The steel bar to be magnetized is placed over the two opposite pole ends of magnets. The rubbing magnets are
placed together over the centre of the bar with a small wooden piece in between. Rubbing magnets are never
lifted off the surface of the steel bar, but rubbed again and again from end to end. Finally ending at the centre
where the rubbing was started.
Divided touch method
Magnets are placed as in the previous case. Rubbing magnets are then moved along the surface of the steel bar
to the opposite ends. Rubbing magnets are then lifted off the surface of the steel bar and placed back in the centre
of the bar. The process is repeated again and again.

Molecular theory of magnetism
In magnetic material such as iron, steel, nickel, cobalt and their alloys, which are ferromagnetic material, the
molecules themselves are tiny magnets ie each of them having a north pole and south pole. This is basically due
to their special crystalline structure and to the continuous movement of electrons in their atoms. Under ordinary
conditions, these molecules arranged themselves in a disorderly manner, the north pole and south pole of these
tiny magnets pointing in all directions and neutralizing one another. Thus a non-magnetised ferromagnetic bar is
one in which there is no definite arrangement of magnetic poles as shown in fig. When iron or steel is magnetized
each molecule are forced to break up their groups and arrange themselves with their north pole in one side and
south pole in other side. In this way one end of the bar becomes north pole and other end the south pole.

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CITS : Power - Electrician & Wireman - Lesson 26-29