Q1 Choose the correct option.

a. A magnet

i. cutting it into two pieces ii using a magnetic keeper

iii. heating. iv. careful handling

Answer: iii. Heating

b. Magnetite is             

i.an electromagnet ii. a natural magnet iii. an artificial magnet iv. not a magnet

Answer: ii. A natural magnet

c. A magnetic compass is used for _____

i. detection of light ii. Navigation iii. measurement of speed iv measurement of current

Answer: ii. Navigation

d. Which of the following materials is non-magnetic?

i. Aluminium ii. cobalt iii. Iron iv. nickel

Answer: i. Aluminum

Q2.Assertion -Reasoning questions

For questions number (i) and (ii), two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

• Both assertion(A) and Reason (R) are true  and Reason (R) is the correct explanation of the assertation (A)
• Both assertion (A) and reason are true and Reason (R) is not the correct explanation of the assertation (A)
• Assertion (A) is true but reason (R) is false
• Assertion (A) is false, but reason (R) is true.

       I. Assertion (A): The strength of an electromagnet can be increased

  Reason  ( R ) : The strength of an electromagnet depends on the flow of current in the coil of the electromagnet

Answer: (a) Both assertion (A) and reason (R) are true, and reason (R) is the correct explanation of assertion (A).
Explanation: The strength of an electromagnet does indeed increase with more current flowing through its coil, making the reason a correct explanation for the assertion.

      II. Assertion: Brass is attracted to a magnet

           Reason: Brass is not a magnetic  substance

Answer: (d) Assertion (A) is false, but reason (R) is true.
Explanation: Brass is not attracted to a magnet because it is a non-magnetic material. Thus, the assertion is false, but the reason is true.

      III. Assertion: Magnetic poles always exist n pairs.

            Reason: Magnetic strength is greatest at the poles.

Answer: (b) Both assertion (A) and reason (R) are true, but reason (R) is not the correct explanation of assertion (A).

Explanation: Magnetic poles do indeed always exist in pairs, and magnetic strength is greatest at the poles. However, the reason does not explain why poles exist in pairs; it merely describes the magnetic strength distribution.

Q3. Answer the following questions in one sentence.

a. Which magnetic pole of the Earth is near its geographical north pole?

Answer: The Earth’s magnetic South Pole is near its geographical North Pole.

b. In which direction does a freely suspended magnet come to rest?

Answer: A freely suspended magnet always rests in the north-south direction.

c.What happens to the poles of a magnet if a magnet is broken into two pieces?

Answer: If a magnet is broken, each piece becomes a new magnet with a north and south pole.

Q4.Answer the following questions in 2-3 sentences.

(a)Distinguish between natural magnets and artificial magnets.

Answer: Natural magnets, like magnetite, are found in nature and have natural magnetic properties. Artificial magnets are made by humans using materials like iron or steel to have magnetic properties. Artificial magnets are stronger and can be shaped.

(b)Classify the following objects as magnetic and non-magnetic: chalk, plastic bottle, blade of a knife, water, rubber band, toothbrush, cork, safety pin

Answer:

• Magnetic objects: Blade of a knife, safety pin
• Non-magnetic objects: Chalk, plastic bottle, water, rubber band, toothbrush, cork

• What are temporary magnets?

Answer: Temporary magnets are objects that act like magnets only for a short time. They become magnets when they are near a strong magnet or when electric current passes through them, but they lose their magnetism after.

Q5.Answer the following questions in3-4  sentences.

a.State any two properties of magnets.

Answer:

• Attraction and Repulsion: Magnets can attract objects made of iron, nickel, and cobalt, and they repel or attract other magnets based on their poles.
• Direction: A freely suspended magnet always aligns itself in the north-south direction, which is why it helps in navigation.

b. Explain the different way by which magnet can be demagnetised?

Answer:

1. Heating: When a magnet is heated, it loses its magnetic power.
2. Hammering or Dropping: Hitting a magnet hard or dropping it multiple times can make it lose its magnetism.
3. Passing AC Current: Passing alternating current (AC) through a magnet can also make it lose its magnetic strength.

c. State the precautionary measures that must be taken to keep magnets safe.

Answer:

1. Avoid Heating: Do not expose magnets to high temperatures as it can weaken them.
2. Careful Handling: Don’t drop or hit magnets hard; it can reduce their strength.
3. Use Magnetic Keepers: Store magnets with magnetic keepers to prevent them from losing strength over time.
4. Keep Away from Electronics: Keep magnets away from devices like computers, as they can affect their functioning.