Magnetism
Primary 6 · Science and Elementary Technology
Magnetism
Lesson 3 of 6
15 min
Let's begin
Gatete's toy train has small magnets at the ends of its carriages. Turned one way, two carriages click together. Turned the other way, they push each other apart, and however hard Gatete tries, he cannot make them touch.
Why does a magnet pull one way and push the other? The answer is in its poles.
Every magnet has two ends where its magnetism is strongest. These are called the poles: the north pole (N) and the south pole (S). The names are short for "north-seeking" and "south-seeking" poles.
Dip a bar magnet into a pile of paper clips. Most clips cling to the two ends and very few to the middle. The magnetic force is strongest at the poles and weakest in the middle.
Tie a thread around the middle of a bar magnet and let it hang freely, away from iron objects. It turns, swings a little and then settles pointing north and south. The end that points north is the magnet's north pole. This happens because the Earth itself behaves like a giant magnet.
If you break a bar magnet in two, you do not get a separate north piece and south piece. Each piece becomes a complete new magnet with its own north and south poles. You can never have a magnet with only one pole.
Suppose you have two metal bars that look the same, and only one is a magnet. Bringing a bar near a magnet and seeing it attracted proves nothing, because a magnet attracts plain iron too. But if one end of the bar repels a pole of a known magnet, the bar must be a magnet, because only a magnet can repel another magnet.
Tip
Opposites attract, likes push back
N and S are friends; N and N (or S and S) quarrel. And remember: only a magnet can repel a magnet.
Try each one on your own first, then tap Show answer to check.
What happens when a north pole is brought near a south pole?
Answer: They attract each other.
What happens when two south poles are brought together?
Answer: They repel each other.
On a bar magnet, where do most paper clips stick?
Answer: At the two ends, the poles, where the force is strongest.
You have two metal bars that look the same. One is a magnet. How can you find out which one?
Answer: Bring each bar near a pole of a known magnet. The bar that repels one end is the magnet, because only magnets repel.
Umutoni breaks a bar magnet into two pieces. How many poles does each piece have?
Answer: Two: each piece has a north pole and a south pole.
What you learned today
Sources and credits
Quick check
Gatete turns two toy carriages so that their magnets push apart, and he cannot make them touch. What is facing each other?
