Static electricity Revise the following How static electricity
- Slides: 9
Static electricity Revise the following: • How static electricity can be created? • Uses of static electricity • Dangers of static electricity
The basics. . . • When 2 insulating materials rub they become electrically charged • Electrons are transferred from one material onto the other making it negatively charged • The material that loses electrons become positively charged • The material that gains electrons become negatively charged
Attract or repel? • When 2 electrically charged bodies are brought together, they exert a force on one another. • Two bodies that carry the same type of charge repel • Two bodies that carry the opposite charges attract
Uses of static electricity 1. Photocopiers and printers 2. Filtering factory smoke (smoke precipitator) 3. Spray painting cars
How does a photocopier use static electricity 1. The copying plate is given a charge. 2. An image of the page to be copied is projected onto the plate. 3. Where light hits the plate, the charge leaks away 4. The charge left on the plate has the same pattern as the black parts of the original page. 5. The charged parts of the plate attract particles of black powder. 6. The black powder is transferred from the plate onto a piece of paper. 7. The paper is heated to make the powder stick 8. This is now a photocopy of the original page.
How does static electricity work in a smoke precipitator? • • • The waste gases and smoke pass through a negatively charged metal grid. The smoke particles are given a negative charge. The smoke particles are repelled from the grid and attracted to the positively charged collecting plates. The smoke particles stick to the positively charged collecting plates. The collecting plates are knocked so the smoke particles fall and can be taken away.
How is static electricity used to spray paint cars? • Spray gun and metal body are attached to a high voltage supply • Car body becomes positively charged and paint in the spray gun becomes negatively charged • Paint droplets are attracted towards the car Remember: It is important to give all droplets a negative charge so that they repel each other (similar charges repel) and so will spread evenly It is important to give the car body a positive charge so that the paint is attracted to it (opposite charges attract)
Dangers of static electricity
The underground storage tanks at petrol stations are filled from tankers. A static electric charge can build up on the tanker as the petrol flows through the pipe to the storage tank. This could be dangerous. • Why is the static electric charge dangerous and what should be done to stop the charge building up? • a spark may cause the petrol vapour to explode/ignite • connect tanker to earth/ground with a conducting wire or earth the tanker