Fun with Magnets

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Magnetic and Non-magnetic materials 

Magnetic materials-

Materials which get attracted towards a magnet are called magnetic material.

Example- Iron, Nickel or Cobalt

Non -magnetic materials-

Materials which do not attract towards a magnet are called non-magnetic materials.

Example- Plastic, Wood

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Poles of magnet

A magnet has two ends or we can say two poles –

•South pole

• North Pole

• Freely suspended bar magnet always comes to rest in the particular direction which is the north-south direction The end of the magnet that points towards the north is called its north-seeking or the north pole of the magnet. The other end that points towards the South are called the South seeking or the South Pole of the magnet.

•All magnet has two Poles whatever their shape may be. ( North and south poles )

•This property of the magnet is very useful for us as for centuries, travellers have been making use of the property of magnet to find direction. Earlier traveller used to find direction by suspending natural magnets while later on, the device was developed based on this property of magnet, it is known as a compass.

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Compass

•It is a small box with glass cover on it. The needle is pivoted inside the box which can rotate freely. The compass has a dial with direction marked on it. It is kept at the place where we wish to know the direction.

•Its niddle is always in a north-south direction when it comes to rest.

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Attraction and repulsion between magnets

•Two similar poles of the magnets repel each other.

• Two, unlike poles, attracts each other.

Few cautions-

Magnets loose their properties if they are:

•Heated

•Hammered

•Dropped from some height.

To keep them safe we should follow below-mentioned precautions-

• Bar magnets 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 horseshoe magnet one should keep a piece of iron across the poles.

•Keep magnet away from mobile, television, music system and computers.

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Exercise

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1. Fill in the blanks in the following

(i) Artificial magnets are made in different shapes such as ________________________ and _____________.

(ii) The Materials which are attracted towards a magnet are called _____________________.

(iii) Paper is not a ____________ material.

(iv) In olden days, sailors used to find direction by suspending a piece of _______________.

(v) A magnet always has __________ poles.

(I) bar magnet, horseshoe magnet, and cylindrical magnet.

(ii) magnetic material.

(iii) magnetic

(iv) natural magnets.

(v) two.

2. State whether the following statements are true or false:

(i) A cylindrical magnet has only one pole. 

(ii) Artificial magnets were discovered in Greece.

(iii) Similar poles of a magnet repel each other. 

(iv) Maximum iron filings stick in the middle of a bar magnet when it is brought near them. 

(v) Bar magnets always point towards North-South direction. 

(vi) A compass can be used to find East-West direction at any place. 

(vii) Rubber is a magnetic material. 

(I) False

(ii) False

(iii) True

(iv) False

(v) True

(vi) True

(vii) False

3. It was observed that a pencil sharpener gets attracted by both the poles of a magnet although its body is made of plastic. Name a material that might have been used to make some part of it.

Answer:

As some part of a pencil sharpener is made up of iron which is a magnetic material, so it gets attracted by both poles of a magnet.

4. Column I shows different positions in which one pole of a magnet is placed near that of the other. Column II indicates the resulting action between them for each situation. Fill in the blanks.

Answer:

5. Write any two properties of a magnet.

Answer:

Properties of magnet are as follows

1. Like poles repel each other where as unlike pole attract each other.
2. It always shows north -south direction when suspended freely.

6. Where are poles of a bar magnet located?

Answer:

Bar magnet has two poles -South Pole and North Pole ,which are located at two ends of a magnet.

7. A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole is located?

Answer:

When bar magnet is suspended freely with the help of thread ,then the pole of magnet which points towards north direction locate the north pole of the magnet .

8. You are given an iron strip. How will you make it into a magnet?

Answer:

– Take a bar magnet and place one of its pole near one edge of an iron strip.

-Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end.

1. -Now Lift the magnet and bring the pole (the same pole you started with) to the same point of the iron bar from which we began.

2. -Move the magnet again along the iron bar in the same direction as you did before.

3. -Repeat this process for about 30-40 times.

4. -Bring a iron filling near the iron strip to check whether it become a magnet if not continue the process for some more time .

9. How is a compass used to find directions?

Answer:

A compass always suspended in north -south direction when it is at rest which is taken as reference to find any other direction.

10. A magnet was brought from different directions towards a toy boat that has been floating in water in a tub. Affect observed in each case is stated in Column I. Possible reasons for the observed affects are mentioned in Column II. Match the statements given in Column I with those in Column II.

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