# 3 Methods of Magnetizing a Steel Bar

- Link: https://studyelectrical.com/2019/12/methods-of-magnetization-steel-bar.html
- Published: 2019-12-16T15:36:54+00:00
- Author: Tesla

In this article, you will learn three principle methods of magnetizing a steel bar.

If a piece of iron or steel is brought near either of the poles of a magnet, it 
is attracted. If a north pole of a magnet is brought near the south pole of another
freely suspended magnet, there is again an attraction between them.

But if two south poles are brought near each other, they repel. The same happens
in the case of two north poles. This means that (i) like poles repel each other 
and (ii) unlike poles attract each other.

From the above, it is clear that a magnet attracts pieces of iron or steel but repels
only magnets. Therefore repulsion is a sure test of magnetism.

Now let’s understand how a can we magnetize a steel bar.

## Methods of Magnetization

There are three principal methods of magnetizing a steel bar as given below:

 1. **Touch method**
 2. **by means of electric current**
 3. **Induction method. **

### 1. Touch Method

This method can be further divided as

 1. Single touch method
 2. double touch method
 3. divided touch method.

#### (a) Single Touch Method

In the single touch method, the steel bar to be magnetized is rubbed with either
of the poles of a magnet, keeping the other pole away from it.

![single touch method of magnetization](https://studyelectrical.com/wp-content/uploads/
2019/12/single-touch-method-of-magnetization-1.png)

Single touch method

![Single Touch method](https://studyelectrical.com/wp-content/uploads/2019/12/Single-
Touch-method.jpg)

Single Touch method

Rubbing is only done in one direction as shown. The process should be repeated many
times for the magnetization of the bar.

#### (b) Double Touch Method

In this method, the steel bar to he magnetized is placed over the two opposite pole
ends of a magnet and the rubbing magnets are placed together over the center of 
the bar with a small wooden piece in between, as shown.

![double touch method of magnetization](https://studyelectrical.com/wp-content/uploads/
2019/12/double-touch-method-of-magnetization.png)

Double touch method

They are never lifted off the surface of the steel bar, but rubbed again and again
from end to end, and finally ending at the center where the rubbing was started.

#### (c) Divided Touch Method

Here the two different poles of rubbing magnets are placed as in the previous case.
They are then separated along the surface of the steel bar to the opposite ends.

The rubbing magnets are then lifted off the surface of the steel bar and placed 
back in the center of the bar. This whole process is repeated again and again as
shown.

![Divided touch method](https://studyelectrical.com/wp-content/uploads/2019/12/divided-
touch-method-of-magnetization.png)

Divided touch method

The steel bar thus magnetized becomes a permanent magnet but the degree of magnetization
is very low.

### 2. By Electric Current

The bar to be magnetized is wound with insulated copper wire and then a strong electric
current (dc) from a [battery](https://studyelectrical.com/2017/09/types-of-rechargeable-batteries.html)
is passed through the wire for some time. The steel bar then becomes highly magnetized.

If the bar is of soft iron, the magnetism remains as long as the current continues
but almost completely disappears as soon as the current ceases. The magnet made 
by such an arrangement is called an electromagnet and is generally used in laboratories.

### 3. Induction Method

This is a commercial method of making permanent magnets. In this method, a pole 
charger is used which has a coil of many turns and an iron core inside it as shown
below. The direct current supply is fed to the coil through a push-button switch.

![sectional view of a pole changer](https://studyelectrical.com/wp-content/uploads/
2019/12/sectional-view-of-a-pole-changer.png)

The sectional view of a pole changer

The steel piece to be magnetized is placed on the iron core kept inside the coil
and the direct current is passed through the coil. The iron core now becomes a powerful
magnet and thus the steel piece placed on it also becomes a magnet by induction.
The magnetized piece of steel is then lifted up after switching off the current.

#### Advantages

The following are the advantages of the induction method of magnetization.

 1. In this method, small pieces of steel can easily be magnetized.
 2. It takes very little time to make a magnet.
 3. Steel pieces of any shape can be magnetized easily.

#### Uses

The induction method is a commercial process for making permanent magnets for speakers,
telephones, microphones, earphones, electrical instruments, magnetos, etc.

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