Exploring MagnetsClass 6 Science NCERT Solutions
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Q1Let us enhance our learning
Fill in the blanks
(i)
Unlike poles of two magnets each other, whereas like poles each other.
(ii)
The materials that are attracted towards a magnet are called
(iii)
The needle of a magnetic compass rests along the __------------ direction.
(iv)
A magnet always has poles.
Solution
(i)
Unlike poles of two magnets attract each other, whereas like poles repel each other.
(ii)
The materials that are attracted towards a magnet are called magnetic materials.
(iii)
The needle of a magnetic compass rests along the north-south direction.
(iv)
A magnet always has two poles.
Q2Let us enhance our learning
State whether the following statements are True (T) or False (F).
(i)
A magnet can be broken into pieces to obtain a single pole.
(ii)
Similar poles of a magnet repel each other. [ ]
(iii)
Iron filings mostly stick in the middle of a bar magnet when it is brought near them.
(iv)
A freely suspended bar magnet always aligns with the north-south direction.
Solution
(i)
False (F). The poles of a magnet always exist in pairs. A single North pole or a single South pole cannot exist, even if a magnet is broken into smaller pieces.
(ii)
True (T). Like poles (North-North or South-South) of magnets repel each other.
(iii)
False (F). Iron filings stick predominantly near the ends of a bar magnet, which are its poles, and very few stick at the middle part.
(iv)
True (T). A freely suspended bar magnet always comes to rest in the north-south direction due to the Earth's magnetic field.
Q3Let us enhance our learning
Column I shows different positions in which one pole of a magnet is placed near that of the other. Column II indicates the resulting interaction between them for different situations. Fill in the blanks. Column I Column II N - N ----------------- N - _--------------- Attraction S - N ____ ____ Repulsion
Solution
The completed table is as follows:
Column I Column II
N - N Repulsion
N - S Attraction
S - N Attraction
S - S Repulsion
Explanation:
- Like poles (N-N or S-S) repel each other.
- Unlike poles (N-S or S-N) attract each other.
Q4Let us enhance our learning
Atharv performed an experiment in which he took a bar magnet and rolled it over a heap of steel U-clips (Fig. 4.15).
According to you, which of the options given in Table 4.3 is likely to be his observation?
Table 4.3: Number of pins attracted by the magnet at its various positions
| Position A | Position B | Position C |
-----|------------|------------|------------|
| Position A | Position B | Position C |
(i)
| 10 | 2 | 10 |
(ii)
| 10 | 10 | 2 |
(iii)
| 2 | 10 | 10 |
(iv)
| 10 | 10 | 10 |
Solution
The correct option is (i).
Explanation:
When a bar magnet is rolled over magnetic materials like steel U-clips, the maximum number of clips will stick to the ends of the magnet, which are its poles. Very few or no clips will stick to the middle part of the magnet. In Figure 4.15, Position A and Position C represent the ends (poles) of the bar magnet, while Position B represents the middle part. Therefore, the number of steel U-clips attracted will be highest at positions A and C, and lowest at position B.
Q5Let us enhance our learning
Reshma bought three identical metal bars from the market. Out of these bars, two were magnets and one was just a piece of iron. How will she identify which two amongst the three could be magnets (without using any other material)?
Solution
Reshma can identify the two magnets and the iron piece by using the property of repulsion, which is the surest test for magnetism.
Here is the method:
- Label the bars: Label the three identical metal bars as A, B, and C.
- Test for repulsion: Take any two bars, for example, A and B. Bring one end of bar A close to one end of bar B.
- Scenario 1: Repulsion is observed. If the two bars repel each other, it confirms that both bar A and bar B are magnets (because only like poles of two magnets repel). In this case, the third bar, C, must be the piece of iron.
- Scenario 2: Only attraction is observed. If bar A and bar B only attract each other (even after trying both ends of one bar against one end of the other), it means that one of them is a magnet and the other is a piece of iron. (A magnet always attracts an iron piece, but an iron piece never repels a magnet).
- In this scenario, take one of these bars (say, A) and test it with the third bar (C). Bring an end of bar A close to an end of bar C.
- If repulsion is observed between A and C, then A and C are magnets, and B is the iron piece.
- If only attraction is observed between A and C (meaning A attracts both B and C from all orientations without repulsion), then bar A must be the iron piece. This would mean that bars B and C are the two magnets.
Q6Let us enhance our learning
You are given a magnet which does not have the poles marked. How can you find its poles with the help of another magnet which has its poles marked?
Solution
To find the poles of an unmarked magnet using a marked magnet, we can use the principle that unlike poles attract and like poles repel.
Method:
- Take the magnet with its poles clearly marked (e.g., North pole and South pole).
- Bring the known North pole of the marked magnet close to one end of the unmarked magnet.
- Observation 1: If the unmarked magnet's end is repelled by the North pole of the marked magnet, then that end of the unmarked magnet is its North pole.
- Observation 2: If the unmarked magnet's end is attracted by the North pole of the marked magnet, then that end of the unmarked magnet is its South pole.
- Once one pole is identified, the other end of the unmarked magnet will naturally be the opposite pole.
Q7Let us enhance our learning
A bar magnet has no markings to indicate its poles. How would you find out near which end its North pole is located without using another magnet?
Solution
To find the North pole of an unmarked bar magnet without using another magnet, we can utilize the property that a freely suspended magnet always aligns itself in the Earth's north-south direction.
Method:
- Suspend the magnet: Tie a thread exactly at the middle of the bar magnet and suspend it from a stand or any support. Ensure the magnet can rotate freely in a horizontal plane and is balanced horizontally.
- Allow it to rest: Gently rotate the magnet and then allow it to come to rest naturally.
- Identify the North pole: The end of the magnet that points towards the geographic North direction is the North-seeking pole (or North pole) of the magnet. The other end will point towards the geographic South direction and is the South-seeking pole (or South pole).
Q8Let us enhance our learning
If the earth is itself a magnet, can you guess the poles of earth's magnet by looking at the direction of the magnetic compass?
Solution
Yes, we can guess the poles of Earth's magnet by observing the direction a magnetic compass needle points.
Explanation:
- A magnetic compass needle is itself a small magnet, with a North-seeking pole (usually marked red) and a South-seeking pole.
- When a compass is placed on Earth, its North-seeking pole points towards the Earth's geographic North direction.
- We know that unlike poles attract each other. Therefore, for the North-seeking pole of the compass needle to point towards the Earth's geographic North, there must be a magnetic South pole of the Earth's magnet located near the Earth's geographic North pole.
- Conversely, the magnetic North pole of the Earth's magnet must be located near the Earth's geographic South pole.
Q9Let us enhance our learning
While a mechanic was repairing a gadget using a screw driver, the steel screws kept falling down. Suggest a way to solve the problem of the mechanic on the basis of what you have learnt in this chapter.
Solution
The mechanic can solve the problem of falling steel screws by magnetizing the tip of the screwdriver.
Method:
- Take a permanent bar magnet.
- Rub one pole of the bar magnet (e.g., the North pole) along the tip of the steel screwdriver, always moving in the same direction, from the handle towards the tip.
- Lift the bar magnet away from the screwdriver tip once it reaches the end, and then repeat the process, bringing the same pole back to the starting point.
- Repeat this process about 30-40 times.
After magnetization, the screwdriver tip will become a temporary magnet. It will then be able to attract and hold the small steel screws, preventing them from falling down while the mechanic is working.
Q10Let us enhance our learning
Two ring magnets X and Y are arranged as shown in Fig. 4.16. It is observed that the magnet X does not move down further. What could be the possible reason? Suggest a way to bring the magnet X in contact with magnet Y, without pushing either of the magnets.
Solution
Possible Reason:
Magnet X does not move down further because there is a strong force of repulsion between magnet X and magnet Y. This occurs when the like poles of the two ring magnets are facing each other (e.g., the North pole of magnet X is facing the North pole of magnet Y, or the South pole of magnet X is facing the South pole of magnet Y). The repulsive force is strong enough to counteract the gravitational force pulling magnet X downwards.
Way to bring magnet X in contact with magnet Y (without pushing):
To bring magnet X in contact with magnet Y, one of the magnets (either X or Y) needs to be flipped over. By flipping one of the magnets, their unlike poles will face each other. This will cause an attractive force between them, allowing magnet X to move down and come into contact with magnet Y.
Q11Let us enhance our learning
Three magnets are arranged on a table in the form of the shape shown in Fig. 4.17. What is the polarity, N or S , at the ends , 4 and 6 of the magnets? Polarity of one end (5) is given for you.
Solution
Given that end 5 is the South (S) pole. We know that unlike poles attract each other when magnets are placed end-to-end, and each magnet has both a North and a South pole.
Let's determine the polarities step-by-step:
- End 5 is South (S). Since end 5 (S) of the bottom horizontal magnet is touching end 4 of the vertical magnet, end 4 must be the North (N) pole for attraction.
- If end 4 of the vertical magnet is North (N), then its other end, end 3, must be the South (S) pole.
- Since end 3 (S) of the vertical magnet is touching end 2 of the top horizontal magnet, end 2 must be the North (N) pole for attraction.
- If end 2 of the top horizontal magnet is North (N), then its other end, end 1, must be the South (S) pole.
- For the bottom horizontal magnet, if end 5 is South (S), then its other end, end 6, must be the North (N) pole.
Therefore, the polarities at the indicated ends are:
- End 1: South (S)
- End 2: North (N)
- End 3: South (S)
- End 4: North (N)
- End 6: North (N)