What it shows
A magnet’s pull passes through paper, cloth, plastic, glass, wood and water, but gets weaker with distance. Only iron, steel and a few other metals block or are pulled by it, and a thick steel sheet shields the pull.
The science
A magnet is surrounded by an invisible region called a magnetic field where its pull can be felt. The field passes straight through most materials, which is why a fridge magnet holds a drawing against the door through the paper. Materials that contain iron, nickel or cobalt are different: they are pulled by the magnet and can also carry the field away, so a steel plate between the magnet and the clip takes the pull for itself and shields the clip. The field grows weaker quickly as you move away from the magnet, so thick layers eventually stop the pull.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A fridge magnet or a bar magnet
- A steel paper clip and a short piece of thread
- Sheets of paper, a cotton cloth, a plastic lid, a glass, a thin wooden board, a steel plate
- A glass of water
- A ruler
Safety
For this project: Keep small magnets and paper clips away from very young children, and never put magnets near a phone or a bank card.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Tie the thread to the paper clip and hold the thread so the clip can be lifted by the magnet without touching it.
Hold one sheet of paper between the magnet and the clip and see whether the clip is still pulled.
Try each material in turn: cloth, plastic lid, glass, wood and finally the steel plate, and tick whether the pull passes through.
Drop the clip into the glass of water and move the magnet along the outside of the glass to drag the clip up the side.
Add sheets of paper one at a time between the magnet and the clip until the pull stops, and count the sheets.
Measure with the ruler how far away the magnet can be before the hanging clip stops swinging towards it.
Test two different magnets and compare the number of sheets and the distance for each.
Draw a chart of materials with a tick for pull passed and a cross for blocked, and write your conclusion.
What you should see
The clip is pulled through paper, cloth, plastic, glass, thin wood and water, but not through the steel plate. The pull fails after a certain number of paper sheets, and a stronger magnet manages more sheets.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1Does a magnet work through water?
Yes, the magnetic pull passes through water just as it does through air.
2Which material stopped the pull?
The steel plate, because steel contains iron and takes the magnet’s pull for itself.
3What happens to the pull as the magnet moves away?
It gets weaker quickly with distance.
4Name three metals a magnet attracts.
Iron, nickel and cobalt; steel is attracted because it is mostly iron.
Take it further
Make a magnet maze: draw a path on a paper plate and guide the clip along it from underneath with the magnet.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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