Solutions
Question 1:
Write the appropriate term in the blanks .
(a) The alloys called.......... and .............. are used for making industrial magnets.
(b) A magnetic field can pass through ............ and ............... .
(c) The intensity of a magnetic field is indicated by the lines of ................ .
(d) The real test of a magnet is .............. .
(a) The alloys called alnico and nipermag are used for making industrial magnets. (b) A magnetic field can pass through cardboard and water. (c) The intensity of a magnetic field is indicated by the lines of magnetic force (d) The real test of a magnet is repulsion.
Question 2:
With whom should I pair up?
| Group 'A' | Group 'B' |
| (a) Compass | 1. The highest magnetic force |
| (b) Door of a cupboard | 2. Like poles |
| (c) Repulsion | 3. A magnet |
| (d) Magnetic pole | 4. A magnetic needle |
Group 'A'
Group 'B'
(a) Compass
4. A magnetic needle
(b) Door of a cupboard
3. A magnet
(c) Repulsion
2. Like poles
(d) Magnetic pole
1. The highest magnetic force
Question 3:
Write answers to the following questions:
(a) Distinguish between the two methods of making artificial magnets.
On repeating this procedure 15 to 20 times again and again, magnetism is developed in the steel bar. This method is called the double-touch method.
Single Touch Method
Double Touch Method
‘N’ pole of one bar magnet is rubbed over a steel bar from the end A to the end B. On repeating this procedure 15-20 again and again magnetism is developed in the steel bar. This method is called the single-touch method.
Taking two bar magnets and placing their two opposite poles at the centre of the steel bar, both the magnets are rubbed over the steel bar from one end to the other such as south pole of one of magnet is at the ‘A’ end and the north pole of the another bar magnet is at the ‘B’ end.
The magnetic strength of the magnet created using this method is low.
The magnetic strength of the magnet created using this method is high as compared to single touch method.
The magnetism of the magnet created using this method lasts for a shorter time.
The magnetism of the magnet created using this method lasts for a longer time as compared to single touch method.
(b) Which substances are used for making electromagnets?
To make an electromagnet we require the following things:
(c) Write a note on 'magnetic field'.
Michael Faradey proposed the idea of magnetic lines of force to explain the magnetic field. The space around the magnet in which the magnetic force acts on an object, is called a magnetic field. The magnetic field around the magnet can be shown with magnetic lines of force Field lines due to a bar magnet is shown below: The magnetism of a magnet acts upon a certain distance from the magnet.
Following are the characteristics of magnetic field lines:
(d) Why is a magnetic needle used in a compass?
The magnetic needle used in a compass freely rotates and always settles in the north-south direction as it is a property of a magnet. Thus, a magnetic needle can be used to ascertain the direction. Thus, in a compass, a magnetic needle is used.
(e) Explain with the help of a diagram how the intensity and direction of the magnetic field of a bar magnet can be determined.
Question 4:
Give detailed information about how the merchants of olden times used a magnet while travelling.
The merchants of olden times used to carry compass for ascertaining directions while travelling. At the oceans where only water is seen everywhere or at the desert areas where only sand is seen everywhere, it becomes difficult to know the direction at night. At that time, the compass used to be helpful for merchants to know the directions.