Fun with Magnets
Overview
Small magnets in fridge doors, pins on boards, compass — everything is the magic of magnets. A magnet attracts some materials towards itself and ignores others. Let us learn the rules of magnets.
Typed Notes
What does a magnet attract?
A magnet attracts only certain materials towards itself — these are called magnetic materials: iron, steel (an alloy of iron), nickel, cobalt. This is why only iron objects stick to a fridge magnet. Materials that do not get attracted — non-magnetic: wood, plastic, glass, paper, cloth, copper, aluminium, gold. That is why a magnet does not work on a copper wire. Test: touch any object with a magnet — if it sticks, it is magnetic; if it does not stick, it is non-magnetic.
Poles — the strength of a magnet
Every magnet has two poles: North (N) and South (S) — one at each end. The magnetic strength is greatest at the poles and least in the middle. That is why pins stick to the ends of a magnet and not to the middle. If you break a magnet into two pieces — each piece still has both N and S poles — a magnet with only a single pole never forms.
Golden rule — attract or repel
Same poles push each other away — repel (N-N or S-S). Opposite poles pull each other — attract (N-S). This is the golden rule of magnets. It can be used as a test: if two magnets are pushing each other away — same poles are facing each other; if they are sticking together — opposite poles are facing each other. Magnetic trains (maglev) work on this principle — they float above the track using repulsion and travel fast without friction.
Compass and Earth's magnetism
A compass is a small box that contains a thin magnetic needle (a small magnet) which can rotate freely. It always stops in the North-South direction — why? Because our Earth is also a big magnet (molten iron moving inside it creates this effect). The N pole of the compass needle is attracted towards Earth's magnetic south — that is why the needle points N-S. Sailors, people in forests, and phone compasses — all rely on this.
Making and taking care of a magnet
Ways to make a magnet: (1) Rub method — rub an iron key or nail with a magnet in the same direction 30-40 times — the key will become slightly magnetic. (2) Electric method — using electric current (we will learn this later). Taking care is also important: dropping, hammering, or heating a magnet reduces its power; store two magnets separately, not touching each other — otherwise the poles can get reversed.
Key Concepts
Revision ke liye ek nazar — exam se pehle yahi padhna hai.
- 01A magnet attracts some materials — magnetic materials: iron, steel, nickel, cobalt. Non-magnetic materials: wood, plastic, glass, paper, copper, aluminium.
- 02A magnet has two poles: North (N) and South (S). Magnetic power is strongest at the poles.
- 03Golden rule: Same poles push each other away (N-N — repel), opposite poles pull each other (N-S — attract).
- 04Compass: a small magnet (needle) that always stops in the N-S direction — it tells us direction. Earth is also a big magnet.
- 05Ways to make a magnet: rub an iron key with a magnet in one direction. Dropping or heating a magnet — reduces its power.
Questions & Solutions
Pehle khud try karo — phir solution kholo. Yahi tariqa topper banata hai.
What materials does a magnet attract? Which ones does it not attract?
What happens when the same poles of two magnets face each other?
How does a compass (direction-finding box) work?
How can the power of a magnet be reduced?
If you break a magnet into two pieces from the middle — what will happen?
Why does a plastic key not stick to a fridge magnet, but an iron key does?
A magnet attracts iron and steel (magnetic materials) but not wood or plastic. It has two poles (N, S) — power is greatest at the poles. Same poles repel each other, opposite poles attract each other. A compass is a small magnet that shows the N-S direction using Earth's magnetism.
Chapter-end quiz
4 MCQsOption tap karo — turant pata chalega sahi ya galat, explanation ke saath.
Q1.Which of these does a magnet NOT attract?
Q2.How many poles does a magnet have?
Q3.What will the N and S poles do to each other?
Q4.What is the purpose of a compass?
Mark karo — dashboard par progress dikhega.