Magnetism
Primary 6 · Science and Elementary Technology
Magnetism
Lesson 5 of 6
15 min
Let's begin
Niyonzima's torch has stopped working, but its batteries still have some energy. His teacher says, "Bring me one battery, a long iron nail and a piece of copper wire, and I will show you how to make a magnet you can switch on and off."
Today you can become a magnet-maker too.
Making a magnet from a piece of magnetic material is called magnetisation. Only magnetic materials such as iron and steel can be magnetised. You cannot make a magnet out of copper, wood or plastic.
You need a bar magnet and a large iron nail or a steel sewing needle.
More strokes make a stronger magnet, up to a limit. The end of the nail where each stroke finishes becomes the opposite pole to the one you stroked with. If you stroked backwards and forwards, you would undo your own work.
An iron nail becomes a magnet easily but loses its magnetism quickly, so it is a temporary magnet. A steel needle is harder to magnetise but keeps its magnetism much longer.
Hang an iron nail from one pole of a magnet. The nail itself becomes a magnet and can hold a second nail, which can hold a third. Now pull the top nail away from the magnet: the chain falls apart, because the nails were only temporary magnets.
You need an iron nail, about one metre of plastic-covered (insulated) copper wire, one dry cell (a 1.5 V torch battery), sticky tape and some paper clips.
This is an electromagnet: it is a magnet only while electricity flows. To make it stronger, wind more turns of wire or use more cells.
Safety: use only small torch batteries, never electricity from a wall socket. The wire and cell get warm, so disconnect after a short time.
Big electromagnets lift scrap iron at scrap yards. They are also found in electric bells, loudspeakers and motors.
Store bar magnets in pairs, side by side, with unlike poles next to each other, and put small pieces of soft iron called keepers across the ends. Do not drop them, and keep them away from heat. Keep strong magnets away from phones and bank cards, which they can damage.
Open the Faraday's Electromagnetic Lab simulation and choose the Electromagnet screen. Change the number of loops in the coil and the battery strength, and watch how the field and the compass change.
Tip
Stroke ONE way, lift HIGH, go back, repeat
For an electromagnet: current ON means magnet ON; current OFF means magnet OFF. More turns, more power.
Try each one on your own first, then tap Show answer to check.
Which of these can be magnetised: an iron nail, a copper coin, a steel needle, a plastic pen?
Answer: The iron nail and the steel needle, because they are magnetic materials.
When you make a magnet by stroking, why must you lift the magnet high at the end of each stroke?
Answer: So you do not stroke backwards on the way back, which would undo the magnetisation.
Give two ways to make an electromagnet stronger.
Answer: Wind more turns of wire around the nail, or use more dry cells.
In a chain of nails hanging from a magnet, why do the nails fall when the top nail is pulled away?
Answer: The nails were only temporary magnets; they lose their magnetism when they are no longer touching the magnet.
Mugisha keeps dropping his bar magnet on the concrete floor. What advice would you give him?
Answer: Handle it gently: dropping a magnet again and again makes it lose its magnetism. Store it with a keeper.
What you learned today
Sources and credits
Quick check
Put the steps for making a magnet by stroking an iron nail in order.
Tap the cards in the right order.
