What this chapter is about
This chapter introduces you to magnets — special objects that can pull certain materials towards them without touching. You may have played with magnets on your fridge door or seen them holding notes on a board. Now you will learn why magnets behave the way they do.
You will discover which materials are attracted to magnets and which are not. You will learn about the two ends of a magnet, called poles, and how poles behave when two magnets come close. You will also find out how a magnet can help us find directions, just like sailors and travellers did hundreds of years ago.
After studying this chapter, you should be able to test materials to see if they are magnetic, identify the poles of a magnet, and understand how a simple compass works.
Key ideas
- A magnet is an object that attracts materials made of iron, nickel, and cobalt. This pulling force is called magnetic attraction.
- Materials that are attracted to magnets are called magnetic materials (like iron nails, steel clips). Materials that are not attracted are called non-magnetic materials (like wood, plastic, glass, paper).
- Every magnet has two ends called poles — the North pole and the South pole. The magnetic force is strongest at the poles.
- Like poles repel each other (push away): North pushes North, South pushes South. Unlike poles attract each other (pull together): North pulls South.
- A freely hanging or floating magnet always comes to rest pointing in the North-South direction of the Earth. This is how a compass works.
- Magnets can attract magnetic materials even through thin barriers like paper, cloth, or water.
- If you break a magnet into pieces, each piece becomes a new magnet with its own North and South poles.
Formulas and facts to remember
1. Magnetic materials: Iron, nickel, cobalt, and steel are attracted by magnets.
2. Non-magnetic materials: Wood, plastic, rubber, glass, copper, and aluminium are not attracted by magnets.
3. Poles of a magnet: Every magnet has a North pole (N) and a South pole (S).
4. Rule of poles: Like poles repel; unlike poles attract.
5. Compass: A small magnet that rotates freely and points towards the North-South direction.
6. Strongest attraction: The pulling force of a magnet is strongest at its two poles, not in the middle.
7. Natural magnet: Lodestone is a naturally occurring rock that acts as a magnet.
8. Magnets lose strength: Heating a magnet, dropping it hard, or hammering it can weaken its magnetic power.
Worked examples
Example 1: Testing magnetic materials
Riya collects five objects from her desk: an iron nail, a wooden pencil, a plastic ruler, a steel paper clip, and an eraser. She brings a bar magnet close to each one. Which objects will the magnet attract?
Solution:
- Iron nail — made of iron, a magnetic material — the magnet will attract it.
- Wooden pencil — wood is non-magnetic — no attraction.
- Plastic ruler — plastic is non-magnetic — no attraction.
- Steel paper clip — steel contains iron, so it is magnetic — the magnet will attract it.
- Eraser — rubber is non-magnetic — no attraction.
So, the magnet attracts the iron nail and the steel paper clip only.
Example 2: Predicting pole behaviour
Aman has two bar magnets. He brings the North pole of the first magnet near the South pole of the second magnet. Then he brings the North pole of the first near the North pole of the second. What happens in each case?
Solution:
- North pole near South pole: These are unlike poles. Unlike poles attract each other, so the magnets will pull towards each other.
- North pole near North pole: These are like poles. Like poles repel each other, so the magnets will push away from each other.
Example 3: Finding direction with a magnet
Priya ties a thread around the middle of a bar magnet and hangs it freely from a stand. After swinging for a while, the magnet stops moving. One end points towards the school gate (North direction). Which pole is that end?
Solution: A freely hanging magnet always settles in the North-South direction. The end pointing towards the North is the North pole of the magnet. The opposite end is the South pole.
Common mistakes
Thinking all metals are magnetic → Only iron, nickel, cobalt, and their mixtures (like steel) are magnetic; copper and aluminium are not.
Believing the middle of a magnet is the strongest part → The poles at the two ends are the strongest; the middle has the weakest pull.
Confusing attract and repel for poles → Remember: like poles (N-N or S-S) repel; unlike poles (N-S) attract.
Thinking a broken magnet loses its poles → Each broken piece becomes a complete magnet with its own North and South poles.
Assuming magnets work only when touching → Magnets can attract through thin materials like paper or even act across a small gap.
Quick revision
- Magnets attract iron, nickel, cobalt, and steel, but not wood, plastic, or glass.
- Every magnet has a North pole and a South pole; strength is greatest at the poles.
- Like poles repel; unlike poles attract.
- A freely suspended magnet points in the North-South direction.
- A compass is a small magnet used to find directions.