Magnetization or methods of making a magnet

Magnetization

This is a process by which randomly arranged molecular magnet of a ferromagnetic material are arranged to point in one direction.

 Methods of magnetization

These include:

• Single touch method.
• Double touch method.
• Electrical method using direct current (d.c.).

 Single touch or single stroke method  

Single stoking

A steel bar (Ferromagnetic material) is stroked several times from end to end using a bar magnet.  The stroking is done in the same direction and using the same pole of bar magnet.

Molecular magnets explanation

The stroking of the magnet pulls the randomly distributed molecular magnets to face in one direction thus material becomes magnetic.

 Disadvantage of single stroke method

The magnet produced has one pole nearer to the end as compared to the other pole

 Identification of a pole

The pole of the bar magnet being used for stroking should be the same pole induced at the end of the steel bar from where stroking starts.

 

Double touch method or double stroke method

This uses two bar magnets placed at the centre of the steel bar with unlike poles as in the diagram. The stroking begins in the middle of the steel bar and ends at the opposite ends. The magnets are raised high at the end of each stroke before another one begins. This prevents reversing the acquired magnetism.

Molecular magnet

As stroking is done, the molecular magnets are pulled to face in one direction therefore creating poles at the ends of the steel bar.

 Advantage of a double touch method over a single touch method  

All poles are at both ends while for single touch method one pole is nearer to end than the other.

Disadvantages of double touch method over a single touch method 

Double touch method is more expensive and tiresome.

 

Electrical method

The steel bar to be magnetized is placed inside a solenoid connected to the cells.

When direct current is switched on for some time, the bar will be magnetized

Note that with a.c. current the bar is not magnetized

 Polarity of steel bar

The polarity of the steel bar depends on the direction in which the current is flowing. Current flows from positive to negative, so if on looking at the end of solenoid, current is flowing in a clock wise direction, that end will be South Pole but if it is flowing anti clockwise the end will be a north pole.

 Induction method

When a magnetic material is kept close to a magnet for long time it gets magnetized.

 

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