Poles of a magnet
The ends of a bar magnet that attracts the iron filings are called poles.
All magnets will have two poles, north (N) and south (S) poles.
The north pole or north-seeking end of the magnet is the end of the magnet that points towards the north. The south pole or south seeking end of the magnet is end that points towards the south.
When a bar magnet is placed in a sheet spread with iron filings, they get attracted towards the ends of a bar magnet.
The magnetic force is maximum at the poles of a bar magnet. A bar magnet is put into a container filled with iron filings. It is observed that more iron filings stick to the poles compared to the center of the bar magnet.
Hoang Ti's chariot
Hoang Ti, an emperor in China, had a statue of a lady in his chariot that could rotate in any direction. The statue had an extended arm, always pointing towards the south. The Emperor used this extended arm of the statue, to locate directions when he went to new places on his chariot.
The direction finder can be made easily by a simple technique.
(CBSE Class 6 chapter 13 'Fun with magnets')
- Suspend a bar magnet on a wooden stand with a thread tied to the middle of the magnet.
- Mark one end of the magnet and rotate it freely.
- When it comes to rest, the position of the ends of the magnet are marked on the ground.
- The line joining these two points show the direction in which the magnet was pointing at rest.
- When we repeat this process, the magnet rests in the same direction again, which is North-South direction.
The direction of the Sun in the morning helps to find the direction towards east. It may not be exact but helps to find North and south direction. Travellers used this method to find directions in olden days.
The compass is a device which is used to find the direction.
It consists of a glass box and a needle. A magnetised needle rotates freely inside the box. A dial is placed inside the box with directions marked on it. The north pole needle coloured in red shows the magnetic pole of the earth. It is to differentiate between magnetic pole and geographic pole of the earth. When the needle comes to rest, it shows the north and south direction.
Our own magnet
We can make our own magnet with the help of a bar magnet.
- Place a rectangular piece of iron on the table.
- Place one end (pole) of a bar magnet near one edge of the iron.
- Till you reach the other end, move the bar magnet along the length of the iron bar.
- Now, bring the pole to the starting point of the iron bar and move it in the same direction again.
- Note that the pole of the magnet and its direction should not change.
- Repeat this process several times and check whether it has become a magnet by using a pin.
- If not, continue the process again until it gets magnetized.
By this method, we can convert an iron nail, a needle or a blade into a magnet.