Magnets: Uses, Materials, and Their Interactions

Introduction:

Nowadays magnets are widely used for many applications. In this session, we will discuss the basics of magnets and their properties, and the way they were and are used.

Explanation:

Magnets:

• A magnet is a material that is capable of attracting things made of or containing iron.
• Most magnets are made up of iron or an alloy of iron.
• They are used for many purposes such as credit cards, toys, cassette tapes, etc.
• They are also used in doorbells, refrigerators, microphones, loudspeakers, etc.
• This property of magnets to attract things made of iron can be used in many ways, one of them being the separation of iron articles from the rest in a heap of garbage.

Magnetic and Non-magnetic Materials:

• The materials which get attracted towards a magnet are called magnetic materials.
• Thus, the hammerhead, the cast iron pan, the tools, and the fridge are all magnetic materials.
• Steel is a magnetic material as it contains a large portion of iron.
• The materials that do not get attracted to a magnet are called non-magnetic materials.
• Thus, the bed, the clothes, the mirror, and all the materials made of plastic are called non-magnetic materials.

Poles of a Magnet:

• When a bar magnet is rubbed in soil containing iron particles, these particles stick to the magnet.
• The amount of iron present in the soil depends on the amount of particles sticking to the magnet.
• It is seen that the iron fillings get attracted more towards certain parts of the magnet.
• The iron fillings 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.

Fig No. 1.2: Poles of a magnet

• A freely suspended bar magnet comes to rest along the Earth’s geographic north-south direction.
• This is because the north pole of the magnet gets attracted towards the magnetic north pole of the earth, which lies close to its geographic south pole and vice-versa.
• This property of the magnets was used for showing directions in olden days.

• 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.

Compass:

• A compass has a magnetized needle pivoted inside a small box with glass cover.
• It has a dial where the directions such as East, West, North and South are marked.
• The needle in the compass is a small magnet which is free to rotate about the pivoted point.
• It always aligns itself in north-south direction.
• Hence, it is used for navigation.

Interaction Between Magnets:

The north pole of a magnet is attracted towards the south pole of another magnet and vice versa.

Also, the north pole of a magnet repels the north pole of another magnet.

It follows that the south pole of a magnet repels the south pole of another magnet.

The unlike poles of two magnets attract each other. Whereas their like poles repel each other.

In other words, the presence of a south pole moves a north pole towards it and a south pole away from it.

And the presence of a north pole moves a south pole towards it and a north pole away from it.

Questions and Answers:

1. Fill in the table using your understanding of magnetic and non-magnetic materials.

Answer

2. 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.

3. What would happen if a bar magnet is brought close to a compass in the ways shown in the figure below?

Answer:

a. When the south pole of the bar magnet is brought close to the compass, the north pole of the compass needle rotates and moves towards it.

And, the south pole of the compass needle moves away from it.

b. When the north pole of the bar magnet is brought close to the compass, the south pole of the compass needle rotates and moves towards it.

And, the north pole of the compass needle moves away from it.