FUN WITH MAGNETS presentation for the class vi students

FUN WITH MAGNETS

1. CHAPTER FUN WITH MAGNETS

2. Learning objective The students will recognize the application of magnets in our day to day life. The students will learn about the discovery of magnets. They will be able to differentiate between natural and artificial magnet as well as between magnetic and non magnetic materials. They will learn about different types of artificial magnet. They will be able to learn about the effect of magnet with the help of an experiment. The students will also learn about the various properties of a bar magnet. The students will learn about the stroking method. They will also learn about precautionary measures to avoid demagnetization. They will also learn how to store of magnets.

3. INTRODUCTION

4. DISCOVERY OF MAGNETS According to Greek legend, magnetism was first discovered by a shepherd named Magnes , who lived in Magnesia, Greece. Magnes was herding his sheep through the mountains. Suddenly he noticed the ferrule of his stick and nails in his sandals got stuck to a rock. The iron in his stick and nails had become attracted to the magnetic rock. The rock was named as magnetite, after the name of the shepherd or the country it was found in. It was also known as a loadstone because of its attractive properties. Magnetite gets attracted to  magnets  and can be easily magnetized to form a permanent magnet. Naturally magnetized pieces of magnetite are called loadstone. Loadstone

5. Types of MAGNETS Example: lodestone Example: bar magnet

6. Artificial magnets Bar magnet U shaped magnet Ball ended magnet Cylindrical magnet

7. Effect of magnet – a paper clip hanging in air

8. MAGNETIC AND NON MAGNETIC MATERIALS MAGNETIC MATERIALS The materials which get attracted towards a magnet are magnetic materials. Example: iron, cobalt, nickel. NON MAGNETIC MATERIALS The materials which are not attracted towards a magnet are non magnetic materials. Example: paper, plastic, soil, fabric etc.

9. MAGNETIC AND NON MAGNETIC MATERIALS

10. Poles of magnet Aim: To show that magnetic force is maximum at the ends of magnets. Materials required: Bar magnet, iron fillings Procedure: Some spread iron fillings on a sheet of paper. Place a magnet over it. Lift the magnet and observe the amount of iron fillings attracted at different locations of the magnet. Observation: The two ends of the magnet attract the maximum iron fillings. In other words, the magnetic force of a magnet is maximum near its end.

11. Finding directions An emperor in China named, Hoang Ti It is said that he had a chariot with a statue of a lady that could rotate in any direction. It had an extended arm as if it is showing a way. It would rest in such a position that its extended arm always pointed towards SOUTH , the Emperor was able to locate directions when he went to new places on his chariot.

12. Finding directions AIM: To show that a magnet always to rest in a fixed directions. MATERIALS REQUIRED: A bar magnet and wooden stand PROCEDURE: Make one end of a bar magnet for identification. Suspend it from a wooden stand with help of a thread. Allow it to come to rest. Mark the direction as the magnet comes to rest. Repeat it 3-4 times with different objects like an a iron bar or a plastic or wooden scale. Record your observation for each object. OBSERVATION: The magnet always comes to rest in the same direction. The direction is found to be the North –South direction. The end of the magnet that points towards North is called its North seeking end or the North pole of the magnet (N). The other end that points towards the South is called South seeking end or the South pole of the magnet (S)

13. MAGNETIC COMPASS This property( aligning in north –south direction) is useful for us. For centuries, travellers have been making use of this property of magnets to find directions. It is said that in olden days, travellers used to find directions by suspending natural magnets with a thread. Later they developed a magnetic compass. A compass is usually a small box with a glass cover on it. A magnetised needle is pivoted inside the box, which can rotate freely. The compass also has a dial with directions marked on it. Its needle indicates the north-south direction when it comes to rest. To find the desired direction, it is rotated until the north and south marks on the dial at the two ends of the needle.

14. MAKE YOUR OWN MAGNET( stroking method/single touch method) Take a rectangular piece of iron, needle or a blade . Place it on the table. Now take a bar magnet and place one of its poles near one edge of the bar of iron. Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end. Now, lift the magnet and bring the pole (the same pole you started with) to the same point of the iron bar from which you began. Move the magnet again along the iron bar in the same direction as you did before. Repeat this process about 30-40 times. Bring a pin or some iron filings near the iron bar to check whether it has become a magnet. If not, continue the process for some

15. Precaution to be taken into account while making your own magnet are: 1 . The pole of the magnet and the direction of its movement should not change. 2. The magnet should not be lifted as it is moved along the length of the iron bar till you reach the other end.

16. MAKE YOUR OWN MAGNET( stroking method/single touch method)

17. ATTRACTION AND REPULSION BETWEEN MAGNETS The opposite (or unlike) poles of the two magnets attract each other. The similar (or like) poles of the two magnets repel each other. These are also called as the Law of Magnets.

18. ATTRACTION AND REPULSION BETWEEN MAGNETS Move towards Move away Move away Move towards

19. Repulsion is a sure test of magnetism Aim: To identify a magnet from two identical bars. Materials required: A stand, thread ,two bar magnets and a bar of iron. Procedure: Suspend both the given bars separately with the help of thread. Take a bar magnet and bring one by one its both the poles closer to the same end of both the bars If both the ends of the of the given bar are attracted by the bar magnet then that bar is of iron. If one end of the given bar is attracted by N-pole of the magnet and is repelled by S-pole of the bar magnet, then that bar is a magnet. Conclusion: Repulsion is a sure test of magnetism 1 II III IV Magnetized iron bar

20. Properties of bar magnet Magnet has two poles : north pole and south pole. The like poles repel and unlike poles attract each other. The maximum attraction is at poles of the magnet and minimum attraction is at the centre. A freely suspended magnet always aligns in north-south direction. It attracts object of iron, nickel and cobalt . It is impossible to  separate  the north and south  poles of a magnet.

21. A few cautions Magnets lose there properties if they are not kept properly. The magnetic properties of a magnet can be destroyed by: Hammering the magnet strongly. Heating the magnet strongly and keeping it in the east-west direction. Striking the magnet against a hard surface repeatedly. Dropping the magnet repeatedly on a hard surface. When the poles of a magnet are left free, the magnet loses its magnetism slowly. This is called self- demagnetisation.

22. Avoiding demagnetisation Bar magnet should be kept in pairs with their unlike poles on the same side. They must be separated by a piece of wood while two pieces of soft iron should be placed across their ends. For horse shoe magnet, one should keep a piece of iron across the poles. Keep magnets away from cassettes, mobiles, television, music system , combat disks (CDs) and the computer

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