Fun With Magnets: NCERT Exercise Solution
Fill in the blanks:
- Artificial magnets are made in different shapes such as __________, __________ and ____________.
Answer: Bar, Horse-shoe, dumb-bell - The Materials which are attracted towards a magnet are called________.
Answer: Magnetic materials - Paper is not a ______ material.
Answer: Magnetic - In olden days, sailors used to find direction by suspending a piece of ___________.
Answer: Magnet - A magnet always has __________ poles.
Answer: Two
State whether the following statements are true or false
- A cylindrical magnet has only one pole.
- Artificial magnets were discovered in Greece.
- Similar poles of a magnet repel each other.
- Maximum iron filings stick in the middle of a bar magnet when it is brought near them.
- Bar magnets always point towards North-South direction.
- A compass can be used to find East-West direction at any place.
- Rubber is a magnetic material.
Answer: 1 False, 2 Fasle, 3 True, 4 False, 5 True, 6 True, 7 False
Answer the following questions:
Question 1: 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: The blade of a pencil sharpener is made of iron. Since iron is a magnetic material, hence pencil sharpener is attracted towards a magnet.
Question 2: 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:
| Column I | Column II |
|---|---|
| N - N | Repulsion |
| N - S | Attraction |
| S - N | Attraction |
| S - S | Repulsion |
Answer the following questions
Question 3: Write any two properties of a magnet.
Answer: Two properties of magnet are as follows:
- A magnet always points to north-south direction, if suspended freely.
- A magnet always has two poles.
Question 4: Where are poles of a bar magnet located?
Answer: At the two ends.
Question 5: A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole located?
Answer: For this, we need to take following steps:
- Tie the bar magnet with a string and suspend it with a horizontal support.
- Allow the magnet to come to rest.
- Mark the end which points to the north, as north pole.
- Repeat the above two steps to confirm.
Question 6: You are given an iron strip. How will you make it into a magnet?
Answer: For this, you need to place the iron piece on a flat surface. Then rub the permanent magnet on the iron piece for many times. Your hand movement should always be in the same direction, while doing this. After some time, the iron piece would attain magnetic property.
Question 7: How is a compass used to find directions?
Answer: A compass has a magnetic needle which can move around a pivot. We know, that a magnet always points to north-south direction. This property of magnet is utilised to find directions with the help of a compass.
Question 8: 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.
Answer:
| Column I | Column II |
|---|---|
| Boat gets attracted towards the magnet | Boat is made of magnetic material |
| Boat is not affected by the magnet | Boat is made up of non-magnetic material |
| Boat moves towards the magnet if north pole of the magnet is brought near its head | Boat is fitted with a magnet with south pole towards its head |
| Boat moves away from the magnet when north pole is brought near its head | Boat is fitted with a magnet with north pole towards its head |
| Boat floats without changing its direction | Boat has a small magnet fixed along its length |