──────────────────────────────────────────────────────── IN-TEXT QUESTIONS ────────────────────────────────────────────────────────
Question:
“Do magnets stick to objects made of certain materials only?”
Answer:
• Yes. Magnets only stick to materials that have iron, nickel, or cobalt in them (these are called magnetic materials). Objects made of wood, plastic, or glass do not stick to magnets.
Question:
“Was your prediction correct for all objects? Which materials stuck to the magnet? What conclusion can you draw?”
Answer:
• Some objects made of iron or steel stuck to the magnet, and some objects made of plastic, wood, or paper did not.
• We can conclude that objects made of iron, nickel, or cobalt are magnetic. Others are non-magnetic.
Question:
“Do all parts of a magnet attract magnetic materials equally? If we repeat this activity with magnets of other shapes, do we get the same result?”
Answer:
• No. The poles (ends) of a magnet have the strongest attraction. The middle parts show less attraction.
• Yes, this happens no matter what shape the magnet is (bar, U-shaped, ring, etc.). The poles always attract more iron filings.
Question:
“Can we find a magnet with a single pole?”
Answer:
• No. Every magnet has two poles: a North pole and a South pole. Even if we break a magnet into pieces, each piece still has two poles.
Question:
“What direction does this line indicate along which the magnet rests? How can we find it out?”
(Refers to a magnet freely suspended by a thread.)
Answer:
• A freely suspended magnet lines up in the north-south direction.
• We can figure out north-south if we know where the sun rises (East) or sets (West).
Question:
“Does it (a magnet) always rest along the north-south direction? What happens if you repeat with an iron bar?”
Answer:
• A magnet always settles along the north-south direction when freely suspended.
• An iron bar (which is not magnetized) can rest in any direction. It does not point north-south on its own.
Question:
“Suppose we place a piece of wood between the compass needle and the magnet. Will this affect the deflection of the compass needle?”
Answer:
• No. The compass needle still deflects. The magnet’s pull can pass through non-magnetic materials like wood, cardboard, or plastic.
Question:
“What do you observe this time?”
(When trying different materials between the compass needle and the magnet.)
Answer:
• Even if we use cardboard, plastic, or a thin sheet of glass, the magnetic pull still works, and the compass needle deflects.
Question:
“What happens when we bring two magnets closer to each other?”
Answer:
• If their unlike poles (North and South) face each other, they attract each other. If their like poles (North-North or South-South) face each other, they repel.
Question:
“Magnets can move some objects without touching them! Is that not amazing?”
Answer:
• Yes, it is very interesting. The magnet’s force can pull or push magnetic objects even from a short distance, without directly touching them.
Question:
“Can we make a garland? Can we take the steel balls out of the maze by moving a magnet below the cardboard tray? Can we pick out a steel paper clip fallen in water using a magnet? Will the two cars speed towards each other or run away from each other?”
Answer (combined for all mini-questions):
• Yes, we can make a garland of small ring magnets by letting them attract each other.
• Yes, we can use a magnet under a cardboard tray to move steel balls through a maze.
• Yes, we can hold a magnet outside a glass or container of water to pull up a steel paper clip.
• If the two matchbox cars each have magnets with like poles facing, they will move away (repel). If they have unlike poles facing, they will move towards each other (attract).
──────────────────────────────────────────────────────── ACTIVITY QUESTIONS ────────────────────────────────────────────────────────
Activity 4.1
Question:
“Collect a few objects made of different materials and a magnet. Predict which objects will stick to the magnet. Test them and write your prediction and observation in Table 4.1. Which materials stuck to the magnet? What conclusion do you draw?”
Answer:
• After testing, objects with iron, nickel, or cobalt stick to the magnet. Plastic, wood, or paper do not.
• Conclusion: Metals like iron, nickel, or cobalt are magnetic materials; others are non-magnetic.
Activity 4.2
Question:
“Spread iron filings on a sheet of paper. Place a bar magnet over them, tap gently, and observe how iron filings stick. Do they stick uniformly or gather more at the ends?”
Answer:
• Most of the iron filings stick near the two ends (poles) of the magnet.
• This shows that a magnet’s poles have the strongest force.
Activity 4.3
Question:
“Hang a bar magnet freely with a string. Rotate it gently and let it come to rest. Mark its ends on the ground or paper. Does it always rest in the same direction each time? What direction is that?”
Answer:
• Yes, it always settles in the same direction.
• A freely suspended magnet rests along the north-south direction.
Activity 4.4
Question:
“Rub an iron needle with a bar magnet (one pole of the magnet) 30 to 40 times in the same direction. Make sure the needle has become a magnet by testing it with iron filings or steel pins. Pass the needle through a cork and float it in water. Does it rest along the same direction each time?”
Answer:
• Yes. The needle, after it becomes a magnet, floats in water along the north-south direction.
• This is like a simple homemade magnetic compass.
Activity 4.5
Question:
“Take two bar magnets (A and B). Place magnet A on top of pencils so it can roll. Bring one end of magnet B near an end of magnet A. Observe if magnet A moves towards or away from magnet B. Then use the other end of magnet B. What do you observe?”
Answer:
• If the North pole of B faces the South pole of A, they attract. If the North pole of B faces the North pole of A, they repel.
• We learn that like poles repel and unlike poles attract.
Activity 4.6
Question:
“Place a magnetic compass and slowly bring a bar magnet’s North pole near the compass needle’s North pole. Observe what happens. Then bring the South pole near the compass needle’s North pole. What do you see?”
Answer:
• When the North pole approaches the North pole of the needle, it moves away (repulsion).
• When the South pole approaches the North pole of the needle, it moves closer (attraction).
Activity 4.7
Question:
“Place a piece of wood (or cardboard/plastic/glass) between the magnet and the compass needle. Observe the needle’s deflection. Is there any change?”
Answer:
• The compass needle still deflects the same way.
• This shows a magnet’s force can pass through non-magnetic materials (like wood, cardboard, plastic, or glass).
──────────────────────────────────────────────────────── EXERCISE QUESTIONS (“Let us enhance our learning”) ────────────────────────────────────────────────────────
Question:
“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.”
Answer:
(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.
Question:
“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.”
Answer:
(i) False
(ii) True
(iii) False (they stick near the poles)
(iv) True
Question:
“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. Fill in the blanks:
N – N → ?
N – S → ?
S – N → ?
S – S → ?”
Answer:
• N – N = Repulsion
• N – S = Attraction
• S – N = Attraction
• S – S = Repulsion
Question:
“Atharv performed an experiment in which he rolled a bar magnet over a heap of steel U-clips at positions A, B, and C (the two ends and the middle). Which of the options is likely to be his observation?
(i) 10 – 2 – 10
(ii) 10 – 10 – 2
(iii) 2 – 10 – 10
(iv) 10 – 10 – 10”
Answer:
• The likely observation is (i) 10 – 2 – 10.
• This means the ends (A and C) attract many U-clips (10 each) and the middle (B) attracts fewer U-clips (2).
Question:
“Reshma bought three identical metal bars. Two are magnets, one is just iron. How can she find which two are magnets without using any other material?”
Answer:
• She can test if any two bars show repulsion. Only magnets can repel each other if like poles face each other. The iron bar is always attracted to a magnet but never repels. So the pair that can repel must both be magnets.
Question:
“You are given a magnet which does not have the poles marked. How can you find its poles with the help of another magnet with poles marked?”
Answer:
• Suspend the unknown magnet freely and bring the known magnet’s North pole close to one end of the unknown magnet.
• If there is attraction, that end of the unknown magnet is its South pole (unlike poles attract). If there is repulsion, that end is its North pole (like poles repel).
• Repeat to confirm.
Question:
“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?”
Answer:
• Suspend the unmarked magnet freely with a thread so it can rotate.
• The end that points towards Earth’s North is the magnet’s North pole.
Question:
“If the Earth is itself a magnet, can you guess the poles of the Earth’s magnet by looking at the direction of the magnetic compass?”
Answer:
• Since the North pole of the compass is attracted to the Earth’s geographic North, the Earth’s magnetic pole in the North must be somewhat like a ‘magnetic South’ (because unlike poles attract).
• This means Earth’s north side is like a magnetic south, and Earth’s south side is like a magnetic north, in terms of magnetic poles.
Question:
“While a mechanic was repairing a gadget using a screwdriver, the steel screws kept falling down. Suggest a way to solve the problem based on what you learned.”
Answer:
• The mechanic can magnetize the tip of the screwdriver by stroking it with one pole of a strong magnet several times in the same direction.
• A magnetized screwdriver can then pick up the steel screws easily.
Question:
“Two ring magnets X and Y are arranged as shown (X is above Y, but not touching). X does not move down further. Why? Suggest a way to bring X in contact with Y without pushing either magnet.”
Answer:
• X and Y have like poles facing each other, causing repulsion. That is why X floats above Y.
• Flip one of the ring magnets so that unlike poles face each other. Then X will move down and make contact with Y.
Question:
“Three magnets are arranged in the shape shown below. Identify the polarity (N or S) at the ends 1, 2, 3, 4, and 6 if the polarity of one end (5) is given.”
Answer:
• If end 5 is marked N, the end it attaches to on the next magnet must be S. You can then follow the pattern that unlike poles meet (N to S, S to N). Also, like poles repel each other and face away.
• The final arrangement depends on how they attract or repel in that shape. By using the rule that magnets join N to S, you can label each end correctly around the figure.