STUDY QUESTIONS
1. (a) You are provided with a 15 cm long steel strip.
By using a permanent bar magnet explain how
you will magnetise the steel strip.
(b) How will you verify the magnetic poles formed
on the steel strip?
(c) Suggest a simple way of demagnetisation of
above steel strip.
2. Why is repulsion considered as surest test of magnetization?
3. How can you make a magnet by the method of touching ? Mention any two methods of touching .
4. You are provided with a 5 cm long and 1/2 cm
thick soft iron rod. How will you convert it into
electromagnet?
5. How are the bar magnets stored? Explain, especially
the role of magnetic keepers.
6. A box contains coins made of nickel and copper.
How will you separate the coins using a powerful
bar magnet?
7. State six important properties of a bar magnet.
8. State four uses of magnets/electromagnets.
9. Distinguish between permanent and temporary
magnets
10. Discuss the ways of demagnetisation
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Answers
Question1.
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.
Answer:
(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.
Question2.
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.
Answer:
A cylindrical magnet has only one pole- False
Explanation:
Poles always exist in pairs in a magnet.
Artificial magnets were discovered in Greece- False
Explanation: -
Natural magnets were discovered in Greece.
Similar poles of a magnet repel each other- True
Explanation:-
Like poles repel each other and unlike poles repel attract each other.
Maximum iron filings stick in the middle of a bar magnet when it is brought near them-False
Explanation:-
Maximum iron fillings 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.
Bar magnets always point towards North-South direction-True
Physics Magnets Iron Fillings
Explanation:-
A freely suspended magnet always aligns itself in North-South direction.
A compass can be used to find East-West direction at any place- True
Explanation: -
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.
Rubber is a magnetic material-False
Explanation: -
Rubber is an insulator. It cannot be attracted or repelled by a magnet.
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:
The blade of sharpener is made up of iron.
Iron is a magnetic material because of this pencil sharpener gets attracted by the poles of a magnet although the body is made up of plastic.
Physics Magnets Sharpener
Question 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.
Physics Magnets Column 1
Answer:
Physics Magnets Column 2
Like magnetic poles repel each other, while unlike magnetic poles attract each other.
Question 5.
Write any two properties of a magnet.
Answer:
Magnets have two poles i.e. North Pole (N) and South Pole(S).
A freely suspended magnet always aligns in N-S direction
Question 6.
Where are poles of a bar magnet located?
Answer:
The poles (north and south) of bar magnet are located at extreme ends of the bar magnet.
Physics Magnets Location of Poles
Question 7.
A bar magnet have no markings to indicate its poles. How would you find out near which end is its north pole located?
Answer:
Tie a bar magnet to a thread and suspends it freely. When suspended freely it will always align itself in north-south direction.
So the end that points to the north direction will be considered as the north pole of the magnet and the end
which points to the south direction will be its south pole.
Physics Magnets Poles of Bar Magnet
Question 8.
You are given an iron strip. How will you make it into a magnet?
Answer:
“Touch and Stroke” method is used to make an iron strip into a magnet.
Take a rectangular piece of iron bar.
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 about 30-40 times.
Bring few all pins near to the iron bar and check if it is converted to a magnet or not.
Physics Magnet Making of a Magnet
Answer:
(A) We can magnetise a steel strip by rubbing it by a bar magnet or letting the bar magnet stay on the magnet for a few days
(B) Take the magnetised strip and tie it to a thread then see the way the ends point The end facing towards the north is the north seeking pole while the other is the south seeking pole.
Repulsion is the surest test of magnetism because a magnet can attract a magnet as well as another magnetic substance
Explanation: