Exploring Magnets

(i) Given/Concept: When two magnets are brought close, unlike poles attract and like poles repel.
Answer: Unlike poles of two magnets attract each other, whereas like poles repel each other.

(ii) Given/Concept: Materials classified on the basis of their behaviour near a magnet.
Answer: The materials that are attracted towards a magnet are called magnetic materials.

(iii) Given/Concept: A freely suspended magnet always aligns along a fixed geographical direction.
Answer: The needle of a magnetic compass rests along the north-south direction.

(iv) Given/Concept: Poles of a magnet always exist in pairs; a single pole cannot exist.
Answer: A magnet always has two (North and South) poles.

(i) Statement: A magnet can be broken into pieces to obtain a single pole.
Answer: False (F)
Reason: When a magnet is broken into pieces, each piece has both a North pole and a South pole. A single pole (monopole) cannot be obtained.

(ii) Statement: Similar poles of a magnet repel each other.
Answer: True (T)
Reason: Like poles (N–N or S–S) always repel each other.

(iii) Statement: Iron filings mostly stick in the middle of a bar magnet when it is brought near them.
Answer: False (F)
Reason: Iron filings mostly stick near the ends (poles) of a bar magnet, where the magnetic force is strongest. Very few filings stick in the middle.

(iv) Statement: A freely suspended bar magnet always aligns with the north-south direction.
Answer: True (T)
Reason: Due to the Earth's magnetic field, a freely suspended bar magnet always comes to rest along the geographic north-south direction.

Concept used: Like poles repel each other; unlike poles attract each other.

Working:
- N – N → Both poles are the same (like poles) → Repulsion
- N – ? → For attraction, the other pole must be unlike → S (i.e., N – S → Attraction)
- S – N → The poles are unlike → Attraction
- ? – S → For repulsion, the other pole must be like → S (i.e., S – S → Repulsion)

Completed Table:

| Column I | Column II |
|---|---|
| N – N | Repulsion |
| N – S | Attraction |
| S – N | Attraction |
| S – S | Repulsion |

Given: A bar magnet is rolled over a heap of steel U-clips. Position A and Position C are the two ends (poles) of the bar magnet, and Position B is the middle portion.

Concept used: The magnetic force is strongest at the poles (ends) of a magnet and weakest at the middle. Therefore, maximum iron clips/filings are attracted at the poles and very few at the middle.

Working:
- Position A (one pole/end) → Maximum clips attracted → 10
- Position B (middle of magnet) → Minimum clips attracted → 2
- Position C (other pole/end) → Maximum clips attracted → 10

Answer: Option (i) — Position A: 10, Position B: 2, Position C: 10 — is the correct observation.

Given: Three identical-looking metal bars — two are magnets and one is a plain iron bar. No other material is available.

Concept used: A magnet attracts an iron bar from both its poles as well as its middle. However, a magnet can only repel another magnet (like poles repel). An iron bar is always attracted to a magnet — it is never repelled.

Method (Step-by-step):

Step 1: Label the three bars as Bar 1, Bar 2, and Bar 3.

Step 2: Bring one end of Bar 1 close to one end of Bar 2.
- If they repel → both Bar 1 and Bar 2 are magnets (since only a magnet can repel another magnet).
- If they attract → one of them could be the iron bar; proceed to Step 3.

Step 3 (if attraction is observed): Now bring the middle portion of Bar 1 close to one end of Bar 2.
- If Bar 2 is attracted to the middle of Bar 1 → Bar 2 is the plain iron bar (iron is attracted everywhere, including the middle, where a magnet has no magnetic force).
- If Bar 2 is NOT attracted to the middle of Bar 1 → Bar 1 is the plain iron bar.

Key Rule: The middle of a magnet has negligible magnetic force. So if a bar is attracted to the middle of another bar, the attracted bar is the iron piece (not a magnet).

Conclusion: The two bars that repel each other (at their ends) are the two magnets. The bar that is attracted to the middle of another bar is the plain iron bar.

Given: One magnet with poles marked (known magnet) and one magnet with poles unmarked (unknown magnet).

Concept used: Like poles repel each other and unlike poles attract each other.

Steps:

Step 1: Hold the known magnet in one hand. Bring its North pole close to one end of the unknown magnet.

Step 2: Observe the interaction:
- If the end of the unknown magnet is repelled → that end is also the North pole (like poles repel).
- If the end of the unknown magnet is attracted → that end is the South pole (unlike poles attract).

Step 3: Once one pole of the unknown magnet is identified, the other end is automatically the opposite pole.

Conclusion: By using repulsion (the sure test for identifying poles), we can correctly identify both poles of the unmarked magnet.