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1 of 20© Boardworks Ltd 2011 Static Electricity. 2 of 20© Boardworks Ltd 2011.

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Presentation on theme: "1 of 20© Boardworks Ltd 2011 Static Electricity. 2 of 20© Boardworks Ltd 2011."— Presentation transcript:

1 1 of 20© Boardworks Ltd 2011 Static Electricity

2 2 of 20© Boardworks Ltd 2011

3 3 of 20© Boardworks Ltd 2011 Static electricity is due to electric charge that builds up on the surface of an insulator, such as a plastic comb. The charge that has built up cannot easily flow away from the insulator, which is why it is called static electricity. What causes static electricity?

4 4 of 20© Boardworks Ltd 2011 All materials are made of atoms, which contain electric charges. An atom has equal numbers of electrons and protons and so has no overall charge. Where does static charge come from? Around the outside of an atom are electrons, which have a negative charge. The nucleus at the centre of an atom contains protons, which have a positive charge. Electrons do not always stay attached to atoms and can sometimes be removed by rubbing. Atoms that have lost or gained electrons are called ions.

5 5 of 20© Boardworks Ltd 2011 Static charge can build up when two insulating materials are rubbed together, such as a plastic comb moving through hair. Friction between the materials causes electrons to be transferred from one material to the other: one material ends up with more electrons, so it now has an overall negative charge one material ends up with fewer electrons, so it now has an overall positive charge. How does static charge build up?

6 6 of 20© Boardworks Ltd 2011 Friction can be used to create a static charge. The insulator ends up with an overall negative charge. The insulator ends up with an overall positive charge. How can static charge be created? If an insulator is rubbed with a cloth, it can become charged in one of two ways: Electrons move from the cloth to the insulator. Electrons move from the insulator to the cloth. OR

7 7 of 20© Boardworks Ltd 2011 Charging materials

8 8 of 20© Boardworks Ltd 2011 Static charge – true or false?

9 9 of 20© Boardworks Ltd 2011 A gold leaf electroscope can be used to detect charge. When the metal plate becomes charged, the charge spreads out through the metal rod and the gold leaf. An electroscope consists of an earthed metal case, inside which a metal rod is connected to a metal plate. The metal rod and the gold leaf gain the same charge, so the thin gold leaf is repelled from the rod and sticks out. A piece of gold leaf is attached to the other end of the metal rod. How can static charge be detected?

10 10 of 20© Boardworks Ltd 2011 A Van de Graaff generator is a machine used to build up static charge. It was invented in 1931 by Robert Jemison Van de Graaff, an American physicist. This machine uses the simple principle of rubbing insulating materials to build up a supply of charged particles. The generator can produce very high voltages and was first used to help scientists study the behaviour of subatomic particles. What is a Van de Graaff generator?

11 11 of 20© Boardworks Ltd 2011 ‘Van de Graaff’ generator

12 12 of 20© Boardworks Ltd 2011

13 13 of 20© Boardworks Ltd 2011 What are the forces between charges? The forces between charges can be investigated using rods made of insulating materials. What happens when two positively-charged acetate rods are placed near each other? The rods repel each other because they have the same overall charge. What will happen if one rod is replaced with a charged polythene rod? rods repel each other acetate rods

14 14 of 20© Boardworks Ltd 2011 How do opposite charges behave? When a charged acetate rod is placed near a charged polythene rod, the rods attract each other. Why does this happen? The polythene rod has an overall negative charge and the acetate rod has an overall positive charge. The overall charges of these rods are opposite and so they attract each other. rods attract each other polythene rod acetate rod

15 15 of 20© Boardworks Ltd 2011 Investigating pairs of charges

16 16 of 20© Boardworks Ltd 2011 Experimenting with static charge

17 17 of 20© Boardworks Ltd 2011 Designing an experiment

18 18 of 20© Boardworks Ltd 2011

19 19 of 20© Boardworks Ltd 2011 Glossary

20 20 of 20© Boardworks Ltd 2011 Multiple-choice quiz


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