Selina Concise Class 6 Physics Solution Chapter No. 6- ‘Magnetism’ For ICSE Board Students.
(a) Artificial magnets are weaker than natural magnets.
(b) Poles of a magnet cannot be separated.
(c) A magnet can attract only a magnetic substance.
(d) A magnet has no effect when it is heated to a high temperature.
(e) Permanent magnets get easily demagnetised.
(f) Magnetic poles occur in pairs.
(g) Single touch method is better than the electrical method for making a magnet.
(h) Magnetic keeper is a wooden piece.
(i) Copper cannot be magnetised.
(2) (a) Temporary magnets are usually made up of ____
Ans. soft iron.
(b) Rough handling destroys the ____ properties of a magnet.
(c) Like poles ____ each other.
(d) A freely suspended magnet points in the ______ direction.
(e) In a magnet, ____ have the maximum attractive property.
(f) A magnet has ____ poles.
(3) Match the following columns solution:
Ans. (a) – (iii), (b) – (ii), (c) – (iv), (d) – (i)
(4) MCQ Solution:
(a) If we suspend a magnet freely, it will settle in-
(i) east-west direction
(ii) north-south direction
(iii) north-east direction
(iv) east-south direction
(b) Making a magnetic substance a magnet by bringing it closer to another magnet without touching it, is
(i) magnetic induction method
(ii) single touch method
(iii) double touch method
(iv) electrical method.
(c) An example of natural magnet is
(iv) none of above.
(d) The artificial magnet used to detect direction in the laboratory is
(i) U-shaped magnet
(ii) horse shoe magnet
(iv) magnetic compass.
Short l Long Answer Questions Solution
1)WHAT IS MAGNET?
ANS:- The substances which have the property of attracting iron are called magnets.
2) WHAT ARE MAGNETIC AND NON MAGNETIC SUBSTANCES? GIVE TWO EXAMPLES OF EACH.
ANS:- The substances which get attracted by a magnet are called magnetic substances. E.g -Iron, steel,Nickel etc.
The substances which do no get attracted by a magnet are called non magnetic substances. E.g- Paper, Rubber, stone etc.
3) WHAT ARE NATURAL AND ARTIFICIAL MAGNETS?
ANS: Natural magnets:- Natural magnets are those which are found in nature called natural magnets. E.g load stone.
Artificial magnets:- Man made magnets are called artificial magnets. E.g- Electromagnet.
4) HOW IS AN ARTIFICIAL MAGNET PREPARED FROM A NATURAL MAGNET?
ANS:- Pieces of ion or other materials are made magnets by rubbing them with natural magnets or passing current through a wire. From this process artificial magnets are made from a natural magnet.
6) HOW CAN MAGNETIC PROPERTIES OF A MAGNET BE DESTROYED?
ANS:- Destroyed by this process given below-
1.By heating. 2 By hammering the magnet. 3. By rough handling.
7) WHY DOES A FREELY SUSPENDED MAGNET ALWAYS REST IN NORTH SOUTH DIRECTION?
ANS:- A freely suspended magnet always rest in north south direction because the north pole of the magnet lies in the geographic north direction and th south pole of the magnet lies in the geographic south direction. So it aligns itself in north south direction.
9) WHY ARE THE ARTIFICIAL MAGNETS PREFFERED OVER THE NATURAL MAGNETS?
ANS:- Artificial magnets are preffered over the natural magnets because the natural magnets are weak and often irregular in shape. They can readily be magnetized and demagnetized by turning the current on or off in the coil.
10) DESCRIBRE AN EXPERIMENT TO SHOW THAT THE MAXIMUN ATTRACTVE PROPERTY IS AT THE POLES OF A MAGNET.
ANS:- Take a bar magnet and place a steel pin at some distance. We observe that nothing happens. Now bring the steel pin near the pole of the bar magnet. We notice that pin sticks to the magnet. This experiment shows that maximum magnetic force acts at poles of the magnet.
11)STATE FOUR IMPORTANT PROPERTIES OF A BAR MAGNET.
ANS:- The important four properties of a bar magnet are:
1)ATTRACTIVE PROPERTY:- A magnet can attract small pieces of iron filling materials or any other ferromagnetic materials.
2)POLES ALWAYS EXIST IN PAIRS:- Single pole can never exist.
3) Same pole always repeal each other and Different poles always attract each other.
4) DIRECTIVE PROPERTY:- If a magnet is suspended horizontally by a thin thread , it rests always pointing north south direction of earth.
12) EXPLAIN THE ATTRACTIVE PROPERTY OF A MAGNET WITH THE HELP OF AN EXPERIMENT.
ANS:- At first we can take iron filling on a piece of paper. Then bring a bar magnet near it. Iron filling cling to it. And it shows the attractive property of a magnet.
14) HOW ARE THE MAGNETS ARE KEPT SAFELY? WHAT IS THE ROLES OF A KEEPERS IN STORING THE MAGNETS.
ANS:- When magnets are not in ise they should be kept and stored in magnetic keepers. The magnetic keeper are the pieces of soft iron. A magnetic keeper has a card board with one or two iron soft pieces. Two magnets are placed in such a way that their opposite poles are close two each other and thena soft iron keeper is attached with it.
17) STATE TWO WAYS OF INCREASING THE STRENGTH OF AN ELECTROMAGNET.
ANS:- The strength of an electromagnet can be increased by:-
1.Increasing the current in the coil.
2.increasing the total number of turns of the coil.
19) STATE THREE IMPORTANT USES OF A MAGNET.
ANS:- Three important uses of a magnets are:-
1.Magnets are used in dynamos,motors,speakers and microphones etc.
2.Magnets are used in toys to give magic effect.
3.Magnets are used in computers,magnetic compass, refrigerators etc.
21) IN WHICH DIRECTION DOES A SUSPENDED BAR MAGNET COME TO REST? GIVE REASON.
ANS:- A magnet always rest in North and South direction. When a magnet is freely suspended its north pole gets attracted by the magnetic south polarity of the earth and it points to the north direction.
22) STATE THREE DIFFRENCES BETWEEN THE TEMPORARY AND PERMANENT MAGNETS.
ANS:- 1. Temporary magnets are made up of soft iron.
And Permanent magnets ae made up of steel,cobalt and nickel.
- Temporary magnets that loses its magnetism as soon as magnetizing force is removed away from it.
And the permanent magnent which does not lose its magnetic properties easily.
3.Temporary magnet is not used to make iron piece into magnet because of its weak power.
And Permanent magnet convert ordinary piece of iron into a temporary magnet.
23) STATE THREE WAYS OF DEMAGNETISING A MAGNET.
ANS:- Three ways of demagnetize of a magnet:-
1.Heating magnet to a very high temperature.
- Passing an alternating current around the magnet.
- Hammering the magnet several times.
24) SUGGEST ONE WAY TO RECOGNISE THE MAGNETIC FIELD OF EARTH.
ANS:- If we suspend a magnet such that it is free to swing.Then we see that it always rest in north south direction. The north pole of the magnet lies in the geographic north direction and the south pole of the magnet lies in the geographic south direction. So it always stay itself in north south direction.
25) NAME THE MATERIAL OF CORE OF AN ELECTROMAGNET FOR A
1.TEMPORARY MAGNET 2. PERMANENT MAGNET.
ANS:- 1, TEMPORARY MAGNET- They are made of soft iron.
- PERMANENT MAGNET:- They are made of iron,steel,cobalt, and nickel.
28) WHAT ARE MAGNETIC KEEPERS? NAME ITS MATERIAL.
ANS:- Magnetic keepers are used to store the magnets. Magnetic keepers are small pieces of soft iron.