[3 Marks Each] QUE-ANS

Question 13 Marks

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)?

Answer

Reshma can identify which two bars are magnets by following these steps:
$1.$ Check for Attraction: Take one bar and bring it near the other two bars. Magnets attract each other, so” if a bar is a magnet, it will pull towards another magnet.
$2.$ Test for Repulsion: After finding one magnet (it attracts another bar), test the remaining bar against the first magnet. Magnets push away from each other when their similar ends (North-North or South-South) are together.
By using these methods of attraction and repulsion, Reshma can figure out which two bars are magnets. The bar that only attract and do not repel the others is likely the piece of iron.

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Question 23 Marks

What is the correct way of storing a bar magnet? Also support your answer with diagram.

Answer

Bar magnet: Two-bar magnets should be placed inside a wooden box so that:
$(a)$ the poles of two magnets lie opposite to each other.
$(b)$ a wooden piece should be kept between the two magnets.

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Question 33 Marks

What are the precautions need to be taken while handling a magnet

Answer

When heated, hammered or dropped from a height, magnets tend to lose their properties. They become weak if they are not stored properly and hence:
→ Bar magnets should be stored in pairs separated by a small block of wood and their unlike poles facing the same side with a soft iron across their ends.
→ A piece of iron should be kept across the poles in case of a horse shoe magnet.
→ Magnets should be kept away from computers, mobiles, televisions etc.
→ Magnets should be handled with care and they should be stored properly.

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Question 43 Marks

How can you show that unlike poles attract each other while like poles repel each other?

Answer

Suspend a magnet on a stand with the help of a string. Now it rests in $N-S$ directions. Take another magnet which has been marked $NTS$ on it and bring $N$-pole of this magnet near the $N$-pole of the suspended magnet. You will find that the suspended magnet rotates and moves away showing that like poles repel each other. The same can be repeated by bringing south-pole of one magnet near south-pole of suspended magnet.
Now you must have found that during the above experiment, south-pole comes towards north-pole and vice versa. It can be repeated by bringing south-pole near a north-pole and north-pole near south-pole of suspended magnet. You will find that unlike poles attract each other.

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Question 53 Marks

shows a magnetic compass. What will happen to the position of its needle if you bring a bar magnet near it? Draw a diagram to show the effect on the needle on bringing the bar magnet near it. Also draw the diagram to show the effect when the other end of the bar magnet is brought near it.?

Answer

The magnetic needle of the compass will get deflected.

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Question 63 Marks

Mark the north-poles of two bar magnets and bring the poles of the magnets near each other, and note down your observations in table.

Answer

poles, facing one another	They are called	We observe
North – South	Opposite poles	Attraction
North – North	Similar poles	Repulsion
South – South	Similar poles	Repulsion
South – North	Opposite poles	Attraction

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Question 73 Marks

Suggest an arrangement to store a $U$ shaped magnet. How is this different from storing a pair of bar magnets?

Answer

$U$ shaped magnet: One metal plate is placed across the two poles of the $U$ shaped magnet.

Bar magnet : Use two metal plates and one wooden block, arrange them as shown in the figure.

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Question 83 Marks

While a mechanic was repairing a gadget using a screwdriver, 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.

Answer

To solve the problem of steel screws falling down while using a screwdriver, mechanic can magnetize the screwdriver. This way, the screwdriver will attract and hold the screws, preventing them from falling.
How to magnetize the screwdriver? (Refer to text 4.5, making your own magnet).

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Science [3 Marks Each] QUE-ANS

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