Practical Activity for 14-16
A demonstration of the principle of electrostatic precipitation.
Apparatus and Materials
- Transparent plastic cup (e.g. Perspex picnic cup)
- Drawing pin
- Aluminium foil
- Smoke source (e.g. paper drinking straw)
Health & Safety and Technical Notes
Read this comprehensive safety note:
Drill a hole in the bottom of the cup. Run a bare wire through the hole to make contact with the Van de Graaff’s dome. Place a small piece of foil at the bottom of the cup, to make contact with the wire. Place a metal lid of foil on top of the cup.
- Place the cup on top of the machine's sphere. Connect its lid to earth.
- Place a drawing pin, point upwards, in the cup. This will ensure a strong local electric field, and ‘electric wind’ to stir the smoke.
- Fill the cup with smoke and run the machine.
- The electric field between the top and the bottom of the container clears the container of smoke as the particles are attracted to the top.
- This principle is used in clearing smoke in a factory chimney. There is a wire down the centre of the chimney and a potential difference between the wire and the chimney walls. The smoke particles collect on the walls and so do not escape into the atmosphere.
This experiment was safety-tested in April 2006
- A video showing how to use a Van de Graaff generator: