Fun with Magnets

Chapter 13

Exercises (অনুশীলনী)

1.    Fill in the blanks in the following:

(i)   Artificial magnets are made in different shapes such as _________ and ________.

Ans:- Bar magnet, Horse-cavalry magnet.

(ii)  The Materials which are attracted towards a magnet are called __________ .

Ans:- Magnetic material.

(iii)  Paper is not a __________ material.

Ans:-  Magnetic.

(iv)  In olden days, sailors used to find direction by suspending a piece of ___________ .

Ans:- magnet.

(v)   A magnet always has ___________ poles.

Ans:-  Two.


2.    State whether the following statements are true and false:

(i)   A cylindrical magnet has only one pole.

Ans:- False.

(ii)  Artificial magnets (কৃত্ৰিম চুম্বক) were discovered in Greece.

Ans:- False.

(iii) Similar poles of a magnet repel each other.

Ans:- True.

(iv) Maximum iron filings stick in the middle of a bar magnet when it is brought near them.

Ans:- False.

(v)  Bar magnets always point towards North-South direction.

Ans:- True.

(vi) A compass can be used to find East-West direction at any place.

Ans:- True.

(vii) Rubber is a magnetic (চুম্বকীয়) material.

Ans:- 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.

Ans:- Although its exterior is made of plastic, the pencil cut part contains a thin blade of iron. So it attracts the two ends of the magnet.


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 (স্তম্ভ) 1 Column (স্তম্ভ) 2
North-North (উত্তৰ-উত্তৰ) __________
North (উত্তৰ) _________ Attraction (আকৰ্ষণ)
South-North (দক্ষিণ-উত্তৰ) __________
_______ South-North (দক্ষিণ) Repulsion (বিকৰ্ষণ)

Ans:-


5.    Write any two properties of a magnet.

Ans:- Any two properties of a magnet are-   

1) The magnet that hangs freely is always north-south mucked.

2) The opposite poles of two magnets attract and the same pole attract each other.


6.    Where are poles () of a bar magnet located?

Ans:- The magnet has two ends:


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:- When a bar magnet is hung freely, it is always in a certain direction, which is in the north-south direction. The head of the magnet which is at the top can be considered as the North Pole and the head which is at the bottom can be considered as South.


8.    You are given an iron strip. How will you make it into a magnet?

Ans:- A thin iron was taken. That piece was placed on a table. Now a bar magnet has been taken and one of its poles has been placed in the iron piece. The magnet was rubbed over the iron piece without lifting it up until the other end reached. Now the process has been repeated by lifting the magnet and putting the same pole back to the place before the iron shot. After doing this 30-40 times, if a pin or a little iron powder is brought close to the iron bar, that bar will attract the sacks like a magnet.



9.    How is a compass used to find directions?

Ans:- A compass is a small box with a glass lid. There is a magnetic shell placed inside the box which can rotate effortlessly. The compass contains a command list marking the direction. The compass is placed at the place where we want to know the direction. When it comes to a stable state, its shell shows the north south direction. The head of the shell is rotated until it matches the north-south direction written in the direction indicator list of the two compasses.


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 affects are mentioned in Column II. Match the statements given in Column I with            those in Column II.

Column (স্তম্ভ) 1 Column (স্তম্ভ) 2
Boat gets attracted towards the magnet Boat is fitted with a magnet with north pole towards its head
Boat is not affected by the magnet Boat is fitted 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

Ans:- 1) The boat is attracted towards the magnet - the boat is made of magnetic material.

2) The boat is not attracted to the magnet - the boat is made of non-magnetic material.

3) The boat comes close to the magnet when it is brought towards the tip of the boat even at the north end of the magnet - the boat has a piece of magnet attached to it. The south pole of the magnet is at the end of the boat.

4) If the north pole of the magnet is brought to the head of the boat, the boat goes away - a magnet is installed in the boat. The north pole of the magnet is at the end of the boat.

5) The boat floats without a change of direction. - There is a small magnet attached to the boat for a long time.




Answer By:- Sourabh Bora