1. Chapter 7 Static Electricity

2. 7.1: Static Charge/Electricity pp. 228
Refers to electric charges that can be collected and held in one place.
“static” means stationary or not moving
Is the temporary transfer of electrons (e-).

4. Current Electricity (Chapter 8)
Refers to the continuous flow of electrons through a material called a conductor in a pathway called a “circuit”.

5. Examples of Static Electricity
Forgetting to put a bounce sheet in the clothes dryer

7. Thunder and Lightening

8. Rubbing a Balloon on Hair/Wool

10. Combing Hair

11. Effect of Friction

12. Subatomic Particles Remember: Protons have a positive charge (p+)
Electrons have a negative charge (e-)
Neutrons have NO charge (n)
When the # of e- is equal to the # of p+ an atom or material is neutral.

13. Types of Charge
If electrons are removed from a neutral object, the object will become positively charged.
•If electrons are added to a neutral object, the object will become negatively charged.

14. Materials can Change Charge
Neutral objects can develop a positive charge by loosing e- or having them redistributed.
Cheerio was once neutral

15. Neutral objects can develop a negative charge by gaining e-
Cont’d
Neutral objects can develop a negative charge by gaining e-

16. Cont’d
Positively charged objects can become neutral by bombarding them with negatively charged objects.

17. Cont’d… Negatively charged objects can become neutral
Add water to absorb excess electrons

20. Insulators Conductors
Materials that DO NOT allow charges to move through easily
If electrons move location they are not replaced by electrons from another location
Can retain static a static charge
Ex. Glass, wood, rubber, ceramics, plastics
Materials that Allow charges to move through easily and freely
Have “free electrons”
Ex. metals

21. Conductors

22. Insulators

24. Electric Discharge Is the removal of electric charge from an object.
Ex. Lightening
“shocks”

26. Discharge after walking on carpet

27. Lightening
Is where static electricity builds up in a cloud and is eventually discharged to the surface and removed.

28. Lightening pp. 244
Is where static electricity builds up in a cloud and is eventually discharged to the surface and removed.

29. Cont’d…

30. Cont’d

31. Getting A Shock

32. Measuring Charge - The Coulomb (C)
The unit of electric charge.
It takes the addition or removal of 6.25 x 1018 electrons to produce 1 Coulomb of charge.
Early scientists detected static charge using an electroscope pp. 229
In 1929 a “lightening machine” was invented called the Van de Graff Generator. Pp. 233

33. Electroscope
If a negatively charged object is brought close to the knob, e- in knob are pushed down the leaves causing the leaves to separate

34. Van de Graff Generator
Moving belt produces a static charge at the base of the generator due to friction
Belt carries charge to top of dome where it collects

36. Applications of Static Electricity
Plastic sandwich wrap
Swiffers and dusters
Air ionizers
Dust removal systems in chimneys
Painting automobiles
Photocopying
Antistatic floors

37. Chimneys, Smokestacks, Factories

38. Photocopiers

39. Electrostatic Air Filter

40. Car Painting

42. Dangers of Static Electricity
Can build up and cause sparks which may lead to explosions, electrical fires and electrocutions
Is prevented by devices which cause “Grounding” to occur
Grounding occurs when a conductor is used to deliver excess charges to the ground to protect people and equipment
Ex. Lightening rods on buildings
Ex. Round prongs on plugs
Ex. cables

43. Lightening Rods
Are metal rods placed on top of buildings and are grounded to Earth by a conducting wire
If lightening strikes the rod, the charge will travel through the wire instead of the building.

45. Grounding Fuel Pumps

46. Electrical Plugs

47. 7.2: Electrical Force pp. 238 1. Force is a push or a pull
a.Contact Force
are forces that have an effect on the objects they touch
Ex. Pushing a desk across the floor or pulling a chair towards your body
b. Action –At-A-Distance Force
is a force that can act on an object without touching it
ex. Electric force

48. Laws of Static Charge pp. 239
1.Like charges repel
2.Unlike charges attract
3.Charged objects attract some neutral ones.

50. Photocopiers pp. 241