Magnetism — Class 6 Science (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 6 Science, Term 3 — Chapter 1. Magnets and their wonderful behaviour.
1. About this chapter
This chapter covers natural and artificial magnets, magnetic and non-magnetic materials, the poles of a magnet, attraction and repulsion, the mariner's compass, and how to store magnets.
2. Magnets and materials
- A natural magnet is lodestone (an ore of iron). Artificial magnets are made in useful shapes — bar magnet, horseshoe magnet, ring magnet.
- Magnetic substances are attracted by a magnet (iron, nickel, cobalt — like pins). Non-magnetic materials are not (paper, rubber, wood).
3. Poles, attraction and repulsion
- Every magnet has two poles — a North pole and a South pole. The pull is strongest at the poles.
- Like poles repel; unlike (opposite) poles attract.
- A magnet can lose its magnetism if it is heated, hammered or dropped roughly.
4. The mariner's compass
- A freely suspended magnet always rests in the North–South direction. This is the basis of the mariner's compass, used to find direction.
- The Chinese made the first mariner's compass; long ago, lodestones were used to find direction.
5. Storing magnets
- Magnets are stored in pairs with unlike poles together, separated by a piece of wood, with two soft-iron keepers placed across the ends — this is keeping/storing magnets so they do not lose strength.
6. Worked examples
Example 1. Which is attracted by a magnet — a plain pin or a paper? The plain pin (iron is magnetic).
Example 2. What happens when two North poles are brought close? They repel (like poles repel).
Example 3. In which direction does a freely suspended magnet rest? North–South.
7. Book-back questions (Samacheer Kalvi)
I. Choose the correct answer
- An object that is attracted by a magnet is a — (a) plastic / (b) plain pin. Ans: (b) plain pin.
- The people who made the mariner's compass for the first time were the — (a) Indians / (b) Chinese. Ans: (b) Chinese.
- A freely suspended magnet always comes to rest in the — (a) East–West / (b) North–South direction. Ans: (b) North–South.
- A magnet loses its property when it is — (a) kept still / (b) hit with a hammer. Ans: (b) hit with a hammer.
- A mariner's compass is used to find the — (a) weight / (b) direction. Ans: (b) direction.
II. Fill in the blanks 6. Materials attracted by a magnet are called magnetic substances. 7. Paper is a non-magnetic material. 8. A magnet has two poles.
III. True or False 9. Similar (like) poles of a magnet repel each other. — True. 10. A cylindrical magnet has only one pole. — False (it has two). 11. Rubber is a magnetic material. — False (it is non-magnetic).
IV. Answer briefly 12. Name the three artificial magnets. — Bar magnet, horseshoe magnet and ring magnet.
8. Common mistakes
- Mistake: Thinking a magnet has only one pole. Fix: Every magnet has two poles — North and South.
- Mistake: Saying like poles attract. Fix: Like poles repel; unlike poles attract.
- Mistake: Calling paper or rubber magnetic. Fix: Paper, rubber and wood are non-magnetic.
9. Quick revision
- Term 3 · Ch 1 · magnetism.
- Natural magnet = lodestone; artificial = bar, horseshoe, ring.
- Two poles (N and S); like repel, unlike attract; strongest at poles.
- Freely suspended magnet rests North–South → mariner's compass (Chinese) finds direction.
- Heating/hammering destroys magnetism; store in pairs with soft-iron keepers.
