Class 6 Fun with Magnets

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Short Answer Type Questions
1. What are magnetic substances?
2. Write three uses of magnets?
3. What do you understand by the directive property of a magnet? State one of its advantages.
4. Differentiate between permanent and temporary magnets.
5. How does an electromagnet differ from a permanent magnet?
6. Differentiate between natural and artificial magnets.
7. What is the proper way of storing bar magnets when not in use? Draw a labelled sketch to show the arrangement?
8. How can self–demagnetisation of magnets be prevented?

Ans:

1. Materials that are attracted by a magnet are called magnetic materials. Examples of magnetic materials include
iron, cobalt, nickel, steel, etc., and their alloys.
2. (i) Magnets are used in magnetic compass used to find directions.
(ii) Magnets are used for the separation of magnetic material and non-magnetic materials.
(iii) Magnets are used to hold objects like a sticker, refrigerator doors, pencil box lids, pins, etc.
3. A freely suspended magnet always rests pointing in the North-South direction. This property of a magnet is called its directive property. This property is used in the magnetic compass and is of help to sailors and navigators.
4. Permanent magnets retain their magnetic properties for very long periods of time. They are made from mixtures of iron, cobalt or nickel with other materials. Temporary magnets retain their magnetic properties
only for a short period of time. They are usually made of iron, cobalt or nickel.
5. Permanent magnets retain their magnetic properties for very long periods of time. They are made from mixtures of iron, cobalt or nickel with other materials. Electromagnets are special types of magnets in which the
magnetism is produced by a flow of electric current.
6. Magnets are the substances which have the property of attracting iron. Magnetic materials that occur freely in nature are called natural magnets. Magnets that are made in laboratories or factories are called artificial magnets.
7. Students do this activity in the class.
8. Self-demagnetisation of magnets are prevented by the following:
(i) We should not drop a magnet on the floor.
(ii) We should not heat a magnet.
(iii) We should store the magnets properly (when not in use).
(iv) We should never hit a magnet with a hammer.
(v) Rough handling of magnets should be avoided.

Long Answer Type Questions
1. Explain how magnets get demagnetized?
2. Describe the construction and working of a magnetic compass.

Ans:

1. The magnetic properties of a magnet can be destroyed by the following methods:
• By heating the magnet strongly and keeping it in the east-west direction
• By hammering the magnet strongly
• By dropping the magnet repeatedly on a hard surface
• By striking the magnet against a hard surface receptively
• By self-demagnetization: when the two poles of a magnet are left free, the magnet loses its magnetism slowly; this is called self-demagnetisation.
2. A magnetic compass is a simple device used for finding direction. It consists of a magnetic needle that can turn freely about its centre. The needle is encased in a box with a transparent top. Directions are either printed on a card placed below the needle or marked on top of the box. Usually, the north pole of the needle is painted red or
blue, or is in the shape of an arrowhead. When kept away from magnetic materials, the north pole of the needle points towards the geographical north. To find directions, the box is turned till the north mark on the card falls exactly below the north pole of the needle. In this position, the other directions are also indicated by the card.

HOTS

1. A carpenter by chance mixes iron nails and screws with wood shavings while working.How can you help him in getting back the nails and screws from the wood shavings?
2. How can you separate metal scrap from a heap of waste materials in a scrap yard?
3. You are given a bar magnet. How will you find out the west direction?
4. A pair of bar magnets is kept in a box with keepers at both the ends. Would this pair act as a magnet?
Give reasoning in support of your answer.

Ans:

1. We can help him in getting back the nails and screws from the wood shavings with the help of a magnet.
2. We can separate metal scrap from a heap of waste materials in a scrap yard with the help of magnets.
3. The two poles of a bar magnet point towards the north and south direction, so the west direction can be easily located.
4. Yes, a pair of bar magnets kept in a box with keepers at both the ends would act as a magnet because the keepers are made up of iron when the magnet is in contact with it, they become a temporary magnet.


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