What it shows
Rubbing some things together gives them an electric charge, called static electricity. A charged comb can pull tiny paper bits and bend a thin water stream.
The science
Rubbing a comb on wool moves tiny charges from the wool to the comb, so the comb becomes charged. A charged object can attract light, uncharged things, such as paper bits and a thin stream of water. This charge stays on the comb and does not flow like current. In a damp climate the charge leaks away, so dry days work best.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A plastic comb (free)
- A dry woollen cloth or your dry hair
- Tiny bits of paper, 1 cm
- A tap with a thin stream of water
- A dry day
Safety
For this project: Do this on a dry day. Never use mains electricity. An adult must help at the tap.
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.
Tear paper into tiny bits about 1 cm wide and spread them on the table.
Hold the comb over the bits and see that nothing happens.
Rub the comb on the wool cloth fast, about twenty strokes.
Bring the comb near the paper bits without touching.
Watch the bits jump up and stick to the comb.
Rub the comb again and hold it near a thin stream of water from the tap.
Look at the stream bend towards the comb.
Write what happens on a dry day and a damp day.
What you should see
The charged comb picks up paper bits and bends the water stream. The effect is weaker on a damp day.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is static electricity?
Charge that stays on an object after rubbing.
2What happens to the comb after rubbing?
It attracts light things.
3Why does it work better on dry days?
Damp air carries the charge away.
4Where do you see static in daily life?
Sparks from clothes or hair standing up after combing.
Take it further
Compare a plastic comb, a steel spoon and a balloon to see which gets charged.
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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