NOTES
Natural Magnet: Magnetite is called natural magnet.
Magnetic materials: The materials which get attracted towards the magnet are known as magnetic materials, e.g., iron, nickel, cobalt.
Non-magnetic materials: The materials which are not attracted towards the magnet are known as non-magnetic materials, e.g., leather, plastic, cloth, paper. Magnetic poles: Magnetic attraction is maximum near the ends of the magnet. These ends are called magnetic poles.
Magnets
Magnets are made of materials that attract objects made of certain substances like iron, cobalt, and nickel.
Magnets come in various shapes and sizes (Fig. 12.1). They can be found as horseshoe, ring, cylindrical, or bar shape.
Not all objects are attracted to magnets. Objects that are attracted by a magnet are said to be magnetic, e.g., iron and nickel. Objects that are not attracted by a magnet, are said to be non-magnetic, e.g., wood and plastic.
Exercise Questions
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.
Solution:
(i) Artificial magnets are made in different shapes such as bar magnet, horse shoe and cylindrical.
(ii) The Materials which are attracted towards a magnet are called magnetic.
(iii) Paper is not a magnetic material.
(iv) In olden days, sailors used to find direction by suspending a piece of magnet.
(v) A magnet always has two poles.
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.
Solution:
i) False
ii) False
iii) True
iv) False
v) True (Freely suspended bad magnet)
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.
Solution:
Iron might have been used to make some part of it.
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.
| Column – I | Column – II |
| N-N | _______ |
| N-___ | Attraction |
| S-N | _____ |
| ___-S | Repulsion |
Solution:
| Column – I | Column – II |
| N-N | Repulsion |
| N- S | Attraction |
| S-N | Attraction |
| S– S | Repulsion |
5. Write any two properties of a magnet.
Solution:
Properties of a magnet are as follows
- It attracts objects made of Nickel, Cobalt and Iron.
- Like poles of two magnets repel each other and opposite poles attracts each other.
6. Where are poles of a bar magnet located?
Solution:
On two ends of a bar 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?
Solution:
A bar magnet is hanged in the air and the end pointing to the north is the north pole of the magnet.
8. You are given an iron strip. How will you make it into a magnet?
Solution:
Take a bar magnet and keep in contact with one of its poles with 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.
- 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.
- Move the magnet again along the iron bar in the same direction as you did before.
- Repeat this process for about 30-40 times.
9. How is a compass used to find directions?
Solution:
A compass always shows north and south direction, by keeping this as a reference we can always find east and west directions also.
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 effects are mentioned in Column II. Match the statements given in Column I with those in Column II.
| Column I | Column II |
| Boat gets attracted towards the magnet | Boat is fitted with a magnet with a north pole towards its head |
| Boat is not affected by the magnet | Boat is fitted with a magnet with a south pole towards its head |
| Boat moved towards the magnet when the north pole is brought near its head | Boat has a small magnet fixed along its length |
| Boat moves away from the magnet when the north pole is brought near its head | Boat is made up of magnetic material |
| Boat floats without changing its direction | Boat is made up of non-magnetic material |
Solution:
| Column I | Column II |
| Boat gets attracted towards the magnet | Boat is made up of magnetic material |
| Boat is not affected by the magnet | Boat is made up of non-magnetic material |
| Boat moved towards the magnet when the north pole is brought near its head | Boat is fitted with a magnet with the south pole towards its head |
| Boat moves away from the magnet when the north pole is brought near its head | Boat is fitted with a magnet with a north pole towards its head |
| Boat floats without changing its direction | Boat has a small magnet fixed along its length |
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