The Secret of Magnets

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1Summary 重點摘要

Magnets attract iron things across space; like poles repel and unlike poles attract; fridge magnets and compasses rely on magnets.

2Vocabulary cards Vocabulary

3Step by step Steps

1. Step 1: Magnets attract ironA magnet has an invisible power called magnetism, and it attracts things made of iron. Try it: a magnet picks up paper clips and an iron spoon, but not a plastic ruler or a wooden pencil. Knowing this feature, we can tell which things are made of iron. Example: to gather paper clips scattered on the floor, sweep with a magnet and the clips jump up at once — fast and fun. A common mistake is thinking a magnet attracts everything; in fact magnets mainly attract iron, while aluminium, copper, plastic and wood are never attracted. Only testing can tell.
2. Step 2: Like poles repelEvery magnet has two poles, called the north pole and the south pole. Slowly bring two north poles together and your hands feel a pushing force, as if someone were saying, Do not touch me; this effect is called like poles repelling. Why does it happen? The same poles push each other away — it is a rule of magnetism. A common mistake is forcing the two magnets together; they will never stick this way, and when they spring apart they may chip or pinch your fingers. Move them close slowly and feel the force with care.
3. Step 3: Unlike poles attractFace one magnet's north pole towards another magnet's south pole, and the two snap tightly together with a click — this is called unlike poles attracting. North and south poles are like a pair of good friends who hug tightly and will not let go. Like poles repel and unlike poles attract; together these two rules are the whole secret of magnets. Example: a magnetic bookmark holds the pages together by the power of unlike poles attracting. A common mistake is thinking any two sides will stick; tell the poles apart first, and you can predict whether the magnets will attract or repel.
4. Step 4: Force passes through thingsMagnetic force is invisible but very powerful, and it can work through some things. Lay a thin sheet of paper over a paper clip and slide the magnet slowly above it; the clip below follows along nicely, like an invisible little bug. It works through card too, showing that magnetism passes through paper. But remember: through things that are too thick, the force grows weak. A common mistake is thinking a magnet must touch an object to attract it; in fact magnetism pulls iron across empty space and through thin paper and card as well.
5. Step 5: Test and recordA magnet experiment needs a plan, just like a little scientist. First guess which of ten items will be attracted and write the guesses down; then test them one by one, recording the results in two columns, attract and not attract. Comparing guesses with results, we find that guesses are sometimes right and sometimes wrong — and that is exactly how learning happens. Why do it this way? Only planned experiments are reliable, and records help us find patterns. A common mistake is testing and then forgetting to record; without a record it is hard to compare and draw conclusions.
6. Step 6: Find magnets in lifeMagnets hide inside many things around us, waiting to be found. Fridge magnets on the refrigerator, the magnetic clip on a schoolbag, fun magnetic blocks and the compass that points the way all use magnets; the edge of a fridge door hides magnets too, keeping the door shut tightly. Hunt for more magnets at home, and you will find that science has been helping our lives all along. A common mistake is thinking magnets live only in laboratories; with careful observation, magnets can be found at home and in the classroom as well.

4Diagrams Diagrams

5Worked example Example

6Common mistakes Mistakes

7Quick check Quick check

8Recap Recap

• Magnetic force is invisible and attracts iron things across space.
• A magnet has two poles: north and south.
• Like poles repel; unlike poles attract.
• The force passes through paper, card and other thin things.
• Fridge magnets, compasses and maglev trains all rely on magnets.