Science Chapter 4: Exploring Magnets - Exercises

📘 Chapter 4: Exploring Magnets

📝 “Let us enhance our learning” (Exercises)

Question 1. Fill in the blanks:

  • (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 2. State whether the following statements are True (T) or False (F):

No. Statement True / False
(i) A magnet can be broken into pieces to obtain a single pole. [ F ]
(ii) Similar poles of a magnet repel each other. [ T ]
(iii) Iron filings mostly stick in the middle of a bar magnet when it is brought near them. [ F ]
(iv) A freely suspended bar magnet always aligns with the north-south direction. [ T ]

Explanation:

  • (i) False: Magnetic poles always exist in pairs; a single isolated pole cannot exist.
  • (iii) False: Iron filings stick mostly near the ends or poles of the magnet where magnetic attraction is strongest.

Question 3. 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 Repulsion
N - S Attraction
S - N Attraction
S - S Repulsion

Question 4. Atharv performed an experiment in which he took a bar magnet and rolled it over a heap of steel U-clips. According to you, which of the options given in Table 4.3 is likely to be his observation?

  • Correct Option: (i) Position A: 10, Position B: 2, Position C: 10.
  • Reason: Positions A and C represent the two poles of the bar magnet, where magnetic attraction is strongest, so maximum U-clips stick there. Position B is the middle part of the magnet where attraction is very weak, so very few clips stick there.

Question 5. 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)?

  • Method: Reshma should take the metal bars and bring their ends close to each other one by one.
  • Identification:
    • Repulsion is the sure test for identifying a magnet.
    • The two bars that show repulsion when their ends are brought close in a specific orientation are the two magnets.
    • The bar that is only attracted to the other two bars and never shows repulsion with any end is the simple iron bar.

Question 6. 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?

  • Take the marked magnet and bring its North pole (N) close to one end of the unmarked magnet.
  • If that end is repelled, it is the North pole (N) of the unmarked magnet, because like poles repel.
  • If that end is attracted, it is the South pole (S) of the unmarked magnet, because unlike poles attract.
  • Repeat the same test for the other end to confirm its pole.

Question 7. 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?

  1. Tie a thread at the middle of the bar magnet and suspend it freely from a stand so that it can rotate horizontally.
  2. Gently rotate the magnet and wait for it to come to rest.
  3. A freely suspended magnet always aligns itself along the geographic North-South direction.
  4. The end of the magnet pointing towards the geographic North direction is its North pole (N).

Question 8. 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?

Yes, we can guess:

  • The North pole of a magnetic compass needle points towards the Earth's geographic North direction.
  • Since opposite magnetic poles attract each other, the Earth's internal magnetic pole located near the geographic North pole must be a magnetic South pole.
  • Similarly, the Earth's internal magnetic pole located near the geographic South pole is a magnetic North pole.

Question 9. 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.

  • Solution: The mechanic can stroke the steel tip of his screwdriver with one pole of a bar magnet repeatedly in one direction to magnetize it, or attach a small magnet to the screwdriver shaft.
  • Reason: Steel is a magnetic material. The magnetized screwdriver tip will attract and hold the steel screws firmly, preventing them from falling during repair work.

Question 10. 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.

  • Possible Reason: The facing surfaces/poles of ring magnet X and ring magnet Y have the same (like) polarity. Since like poles repel each other, magnet X experiences magnetic repulsion and floats above magnet Y.
  • Way to bring in contact: Remove magnet X, flip it upside down (invert its sides), and slide it back onto the stand. Now, unlike (opposite) poles will face each other, resulting in magnetic attraction, and magnet X will move down to touch magnet Y.

Question 11. 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 1, 2, 3, 4 and 6 of the magnets? Polarity of one end (5) is given for you (5 - N).

Magnetic poles always exist in pairs and opposite poles attract each other:

  • End 5 = N (Given)
  • End 6 = S (Opposite end of the same bar magnet)
  • End 4 = S (Attached to End 5 (N), so unlike pole attracts)
  • End 3 = N (Opposite end of the same bar magnet)
  • End 1 = N (Attached to End 6 (S), so unlike pole attracts)
  • End 2 = S (Opposite end of the same bar magnet)

🔬 “Learning further” (Projects & Activities)

  • Comparing Magnetic Strength: Take 3–4 different magnets and test how many steel U-clips each magnet can pick up. The magnet that picks up the highest number of clips has the strongest magnetic strength.
  • Toy 'Hopping Frog' Project: Fix ring magnets with alternating N-S poles along a ruler using glue. Glue a paper frog with a ring magnet onto a flexible plastic strip. Sliding the strip over the ruler causes the frog to hop due to magnetic repulsion and attraction.
  • Maglev Train Model: Research Maglev (Magnetic Levitation) trains that float above tracks using magnetic repulsion to eliminate friction and travel at high speeds.
  • Magnets of Different Shapes: Magnets are manufactured in various shapes (Bar, U-shaped, Ring, Disc, Cylindrical) to suit different practical uses in speakers, pencil boxes, compasses, and toys.
  • Magnets in Medicine: Powerful magnets are used in MRI (Magnetic Resonance Imaging) machines in hospitals to generate detailed images of internal organs of the human body for medical diagnosis.
💡 Teacher's Tip: Note down all these answers cleanly in your Science notebook. Handle magnets with care—do not heat, hammer, or drop them from a height to preserve their magnetism! 🧲

Note: If there are any errors in the provided answers or details, please contact us at trhelpmail@gmail.com.