Q.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) Artificial magnets are made in different shapes such as bar-magnet, cylindrical magnet and horse-shoe magnet.
(ii) The Materials which are attracted towards a magnet are called magnetic material.
(iii) Paper is not a magnetic material.
(iv) In olden days, sailors used to find direction by suspending a piece of bar-magnet.
(v) A magnet always has two poles.
Q.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: A magnet of any shape always has two poles; North pole and south pole.
(ii) False: Natural magnets were discovered in Greece.
(iii) True: Like poles repel each other and unlike poles attract each other.
(iv) False: Maximum iron filings will stick to the ends of the bar magnet because at the ends of the magnet poles are located. The strength of the poles is maximum at the ends of the magnet.
(v) True: A freely suspended magnet always aligns itself in North-South direction
(vi) True: Always the needle of the compass points towards North-South direction. So if North-South direction is known then East-West direction can also be known.
(vii) False: Rubber is an insulator. It cannot be attracted or repelled by a magnet.
Q.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.
Ans. There is a blade in pencil sharpener which is made up of iron. Iron is a magnetic material that is why it is attracted by the poles of magnet.
Q.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.
N - N
N - ______
S - N
______ - S
N - N
N - S
S - N
S - S
Q.5. Write any two properties of a magnet.
Ans. Two properties of magnet are as follows:
(i) Like magnetic poles repel each other and unlike magnetic poles attract each other.
(ii) A freely suspended magnet always aligns in N-S direction.
Q.6. Where are poles of a bar magnet located?
Ans. The poles of bar magnet are located at its two end points.
LONG ANSWER TYPE QUESTION
Q.7. A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole located?
Ans. Location of the poles of as magnet can be determined by suspending it freely. A freely suspended bar magnet always points in the north−south direction. The end that points towards north direction is the north pole of the magnet while the end that points towards south direction is the south pole of the magnet.
Q.8. You are given an iron strip. How will you make it into a magnet?
Ans. An iron strip can be converted into a magnet by following method:
Place the iron strip on a table. Place one pole of a bar magnet near one end of the iron strip. Move the bar magnet along the length of the iron strip starting from one end to the other end as shown in the following figure. Then, lift the magnet and bring the pole to the starting point and move in the same direction as before.
On repeating this process for at least 30-40 times, the iron strip will become a bar magnet with two poles.
Q.9. How is a compass used to find directions?
Ans. A compass has a magnetic needle that can rotate freely. When a compass is kept at a place, the magnetic needle aligns in north-south direction. Red arrow of the compass needle is termed as the north pole and the other end as south pole.
Q.10. A magnet was brought from different directions towards a toy boat that has been floating on water in a tub. The effect 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.
Boat gets attracted towards the magnet
Boat is fitted with a magnet with north pole towards its head
Boat is not affected by die magnet
Boat is filled with a magnet with south pole towards its head
Boat moves towards the magnet if north pole of the magnet is brought near its head
Boat has a small magnet fixed along its length
Boat moves away from the magnet when north pole is brought near its head
Boat is made of magnetic material
Boat floats without changing its direction
Boat is made up non-magnetic material
|Column I||Column II|
|Boat gets attracted towards the magnet.||Boat is made of magnetic material.|
|Boat is not affected by die magnet||Boat is made of a non-magnetic material|
|Boat moves towards the magnet if north pole of the magnet is brought near its head||Boat is filled 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|