Unit 3 Static Electricity

1. Unit 3 Static Electricity Objectives: • Discuss the nature of static electricity. • Use an electroscope to determine unknown charges. • Discuss lightning protection. • List nuisance charges of static electricity. • List useful charges of static electricity.

2. Unit 3 Static Electricity Static charges can cause a painful shock!

3. Unit 3 Static Electricity Charges • Static charges can be a nuisance, or dangerous, or beneficial. • Electric shocks from walking on carpet can be annoying. • Electrostatic discharge can ruin sensitive electronic components. • Copy machines and sandpaper rely on the application of static electricity.

4. Unit 3 Static Electricity Grains of sand receive a charge to help them stand apart when making sandpaper.

5. Unit 3 Static Electricity Charges • Electronic air filters called precipitators use static charges to attract small particles in the air and trap them in the filter. • The word static means not moving. • Electrostatic charges build up on insulators. • A static charge can be positive or negative.

6. Unit 3 Static Electricity Electronic air cleaner or precipitator

7. Unit 3 Static Electricity Producing a static charge.

8. Unit 3 Static Electricity Electroscope • The electroscope was an early device that indicated the polarity of a charged object. • The electroscope uses a metal ball to transfer a known polarity charge to thin metal leaves. • When an object with an unknown charge is brought near the metal ball, the action of the leaves reveals the nature of the object’s charge.

9. Unit 3 Static Electricity Electroscope.

10. Unit 3 Static Electricity Charging the electroscope with a negative static charge.

11. Unit 3 Static Electricity The action of the leaves reveals the polarity of the pen’s charge.

12. Unit 3 Static Electricity Lightning • The best example of static electricity in nature is lightning. • The movement of water droplets in a thundercloud generates a static charge. • Lightning occurs when the positive and negative areas have the potential difference to overcome the air’s resistance.

13. Unit 3 Static Electricity The typical thundercloud contains areas both positively and negatively charged.

14. Unit 3 Static Electricity Lightning Protection • Lightning rods are used to help protect objects from lightning. • Lightning rods provide a safe path to channel the electric discharge. • A lightning arrestor is also used for protection.

15. Unit 3 Static Electricity Lightning travels from negative to positive areas.

16. Unit 3 Static Electricity A lightning rod provides an easy path to ground.

17. Unit 3 Static Electricity Useful static charges are often used in spray painting.

18. Unit 3 Static Electricity The drum of a copy machine is coated with selenium.

19. Unit 3 Static Electricity The drum receives a positive charge.

20. Unit 3 Static Electricity The image is transferred to the selenium drum.

21. Unit 3 Static Electricity Negatively charged powder is applied to the positively charged drum.

22. Unit 3 Static Electricity The negatively charged powder is attracted to the positively charged paper.

23. Unit 3 Static Electricity • Review: • The word static means not moving. • An object is positively charged by removing electrons. • An object is negatively charged by adding electrons. • An electroscope is a device used to determine the polarity of an object.

24. Unit 3 Static Electricity • Review: • Static charges accumulate on insulator materials. • Lightning is an example of a natural static charge.