More About Magnets – Poles of the Magnet

More About Magnets 

 Key Concepts

1. Poles of magnet
2. Finding directions using a magnet

Introduction

Magnets attract objects made of iron or contain iron. The objects which get attracted to magnets are called magnetic materials. Additionally, these objects do not get attracted to all the parts of the magnet equally. In this section, we will learn the reason for this. 

Explanation

Poles of a magnet: 

When a bar magnet is rubbed in soil containing iron particles, the particles stick to the magnet non-uniformly on its surface. The iron fillings get attracted more towards certain parts of the magnet. They get attracted to the ends of the bar magnet more than its other parts. The poles of a magnet are said to be located near these ends of a bar magnet. 

The same thing can be seen if a magnet of any other shape is used in a similar way. The iron fillings get attracted to the ends of the horseshoe magnet more than its other parts. The poles of a horseshoe magnet are said to be located near its ends. The same method can be used for magnets of any other shape or size to locate their poles such as ring, cylindrical etc. 

Finding directions using a magnet: 

In ancient times, people used to locate places using magnets fitted to their chariots, which used to show directions for the people to travel. A Chinese king named Hoang Ti had a statue of a lady in his chariot which could rotate freely in any direction. The extended arm of the statue always used to point towards the south. This extended arm was used by the king to locate directions when he went to new places.  

Activity: 

An activity can be performed to know the way magnets can be used to locate directions. The steps to be followed are as follows: 

• Take a bar magnet, mark one of its edges, tie it with a thread and suspend it using a stand as shown. 
• The magnet then rotates freely and comes to rest. 
• After it comes to rest mark two points on the ground which show the position of the ends of the magnet. Join them to draw a line, which shows the direction of the magnet. 
• These artificial magnets are made in various shapes such as bar magnet, ring magnet, horseshoe magnet, magnetic needle, disc magnet etc. 
• Rotate the magnet by pushing one of its ends and let it come to rest. Mark the points which show its position and join them to form a line. 
• Repeat this process again. This gives another line of orientation of the magnet. 
• It will be found that the magnet always comes to rest in the same position every time it is disturbed. 
• When the same activity is repeated using an iron bar, a plastic pipe or a wooden bar, the same result is not obtained, as these do not rest in the same position every time. 

Thus, a freely suspended bar magnet always comes to rest in the same direction, i.e., the north-south direction. 

The following steps can be done to check the directions pointed by a freely suspended bar magnet. 

• To check this, one can use the direction of the rising sun as shown in the picture. 
• Stand facing the sun while sunrise and stretch your arms as shown in the picture, your left and right arms point towards north and south respectively. 

• Match the lines that you have drawn while with this north-south direction. 
• Using this method one can figure out which end of the magnet is facing north and which one is facing south. 

Hence, the mystery behind the statue in the king’s chariot is solved. The statue might have a magnet which points in the north-south direction always. 

Poles of the magnet: 

The end of the magnet which points towards north is called the north seeking pole and the end of the magnet which points towards south is called the south seeking pole. Magnets have two poles i.e., north and south poles irrespective of shape and size. These poles are usually marked on the body of the magnet itself. 

Question and Answer: 

Do the iron fillings stick the magnet uniformly throughout its surface? Why? 

Answer: 

No, the iron fillings do not stick to the magnet uniformly. They get attracted more towards the ends of the magnet where the poles are located. 

Summary

1. The poles of a magnet are located near the ends of the magnet to which the iron fillings
   are greatly attracted.
2. The poles of a horseshoe magnet are said to be located near its ends.
3. A freely suspended bar magnet always comes to rest in the same direction i.e., the north
   south direction.
4. The end of the magnet which points towards north is called the north seeking pole and
   the end of the magnet which points towards south is called the south seeking pole.
5. Magnets have two poles i.e., north and south poles irrespective of shape and size.
6. These poles are usually marked on the body of the magnet itself.