CHAPTER- 10 FUN WITH MAGNETS
Notes
1. Magnet– Substances that have the property of attracting iron are called magnets.
2. Artificial Magnet– The method of making a magnet from pieces of iron is called an artificial magnet.
- Nowadays, artificial magnets are made in various shapes. For example: bar magnet, horseshoe magnet, cylindrical magnet, and spherical magnet.
3. Magnetic Substances– Substances that are attracted towards a magnet are called magnetic substances. example: iron, nickel, and cobalt.
4. Non-magnetic Substances– Substances that are not attracted towards a magnet are called non-magnetic substances.
5. Poles of a Magnet– The end of a magnet that points towards the north is called the north-seeking end or the north pole. The other end is called the south-seeking end or the south pole.
- All magnets have two poles, no matter what their shape is.
- The north (N) and south (S) poles are marked on magnets.
6. In ancient times, travelers used to carry a natural magnet with them, which they would hang by a thread to determine direction.
7. Compass– A compass is generally a small box with a glass cover. A magnetized needle is fixed on a pivot inside the box, which can rotate freely.
- A compass has a dial on which the directions are marked.
- When at rest, its needle points in the north–south direction.
8. Unlike poles of two magnets attract each other, while like poles repel each other.
EXERCISE
Question- 1. Fill in the blanks in the following:
(1) Artificial magnets are made in different shapes such as _______, ________ and ________.
(2) The materials which are attracted towards a magnet are called _______.
(3) Paper is not a ______ material.
(4) In olden days, sailors used to find direction by suspending a piece of ________.
(5) A magnet always has ________ poles.
Answer- (1) Artificial magnets are made in different shapes such as Bar magnet, horseshoe magnet and Spherical magnet.
(2) The materials which are attracted towards a magnet are called Magnetic substances.
(3) Paper is not a Magnetic material.
(4) In olden days, sailors used to find direction by suspending a piece of Bar magnet.
(5) A magnet always has Two poles.
Question- 2. State whether the following statements are True or False:
(1) A cylindrical magnet has only one pole.
(2) Artificial magnets were discovered in Greece.
(3) Similar poles of a magnet repel each other.
(4) Maximum iron filings stick in the middle of a bar magnet when it is brought near them.
(5) Bar magnets always point towards North-South direction.
(6) A compass can be used to find East-West direction at any place.
(7) Rubber is magnetic material.
Answer- (1)- False, (2)- False, (3)- True, (4)- False, (5)- True, (6)- True, (7)- False.
Question- 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- A pencil sharpener contains a blade which is made of iron. Since iron is a magnetic substance, it is attracted by the poles of a magnet.
Question- 4. Column 1 shows different positions in which one pole of a magnet is placed near that of the other. Column 2 indicates the resulting action between them for each situation. Fill in the blanks.
Question- 5. Write any two properties of a magnet.
Answer- Two properties of a magnet –
1. The opposite poles of a magnet attract each other, while the like poles repel each other.
2. A magnet helps us to find directions.
Question- 6. Where are poles of a bar magnet located?
Answer- The poles of a bar magnet are located at its two end points.
Question- 7. A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole located?
Answer- Suspend a bar magnet freely with the help of a light thread. When the magnet comes to rest, it aligns itself in the north–south direction.
Question- 8. You are given an iron strip. How will you make it into a magnet?
Answer- 1. Take an iron strip and a bar magnet.
2. Place one pole of the bar magnet at one end of the iron strip.
3. Without lifting the magnet, rub it along the entire length of the strip to the other end.
4. Lift the magnet, bring it back to the starting end, and rub it again in the same way.
5. Repeat this process about 40–50 times. By this process, the iron strip will become a magnet.
6. Bring some iron objects near the iron strip and check whether it has been converted into a magnet or not.
Question- 9. How is a compass used to find directions?
Answer- A compass is a small box with a glass cover that contains a magnetized needle mounted on a pivot, which can rotate freely. The compass has a dial on which the directions are marked.
To find directions, the compass is placed at the location where we want to determine them. When at rest, the needle of the compass points in the north–south direction.
Question- 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 1. Possible reasons for the observed affects are mentioned in Column 2. Match the statements given in Column 1 with those in Column 2.
