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Do Now: 1.What does the word “charge” make you think of? 2.What is the definition of the word “static”? 3.Describe the parts and structure of an atom.

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Presentation on theme: "Do Now: 1.What does the word “charge” make you think of? 2.What is the definition of the word “static”? 3.Describe the parts and structure of an atom."— Presentation transcript:

1 Do Now: 1.What does the word “charge” make you think of? 2.What is the definition of the word “static”? 3.Describe the parts and structure of an atom.

2 Chapter 20 Static Electricity

3 Electrostatics The study of charges that can be collected and held in one place

4 With your “elbow partner” come up with examples where charge differences build up in nature, and describe the consequences

5 Charge Caused by an electron imbalance as electrons move

6 Atomic Charge In neutral atoms the number of electrons = the number of protons

7 Charge Opposite charges attract & like charges repel

8 charge conservation: electric charge can neither be created nor destroyed. electric charge

9 Millikens Oil Droplet Experiment

10 Electron Charge 1.60 x 10 -19 C C = Coulombs

11 Charge The charge of an object leaks off into water molecules in air

12 Charge Charged objects eventually return to their neutral state

13 Charge Holding a charge is easy on dry days & difficult on humid days

14 Conductors Materials like metals that allow electrons or charges to move

15 Common Conductors Copper, silver, gold, aluminum, & graphite

16 Insulators Materials that will not allow electrons or charges to move easily

17 Common Insulators Glass, dry wood, plastic, rubber, & dry air

18 Electron Sink Anything that can absorb lots of electrons

19 Common Electron Sinks People, Earth, etc

20 Electroscope A device used to detect electrical charge

21 Charge Redistribution Conduction Induction

22 Charge by Conduction Charge by touching a charged body to a neutral body

23 Charge by Induction Charge by moving a charged body near a neutral body

24 Charge Separation on Neutral Objects - - - + - - - + - - - + - + - + - + + + - + + + - + + +

25 Do Now (9/1/11): On half- sheet of paper: #5 is True

26 Electrical Force Force caused by the attraction or repulsion of charges

27 Coulomb’s Law Force between charges is proportional to charge & inversely proportional to distance between charges

28 Coulomb’s Law F  q A q B

29 Coulomb’s Law F  1d21d2

30 Coulomb’s Law F  q A q B d 2

31 F e Formula F e = k q A q B d AB 2

32 Electric Constant k = 9.0 x 10 9 Nm 2 C 2

33 Identify another formula that is very similar to the electrical force formula

34 Gravity Formula F g = G m A m B d AB 2

35 Electrical Force Electrical force must be much greater than gravitational force

36 Do Now (9/2): Complete the half-sheet of paper on your desk. Leave #1 and 2 blank

37 Subatomic Particles 9/2/2011

38 Subatomic particle masses Electron: 9.1093 x10 -31 kg Proton: 1.6726 x 10 -27 kg Neutron: 1.6749 x 10 -27 kg

39 Review: Electron Charge 1.60 x 10 -19 C C = Coulombs

40 Elementary charge e = 1.60 x 10 -19 C

41 Subatomic Particle Charges Electron: -e Proton: e Neutron: 0

42 Working with Coulomb’s Law Algebraically Given q in terms of other q q’s are equal to

43 Do Now: On half-sheet of paper

44 Agenda: Homework questions – 5- 10 min Quiz – 10 – 15 min Work on homework – rest of class

45 Calculate the electrical force occurring when a ball with a charge of 2.0 x 10 -8 C is 12 mm from another ball with a charge of -3.0 x 10 -8 C:

46 Calculate the electrical force occurring when a ball with a charge of 3.0 x 10 -4 C is 12 mm from another ball with a charge of -6.0 x 10 -6 C:

47 Calculate the force between 2 electrons 8.0 x 10 -3 nm apart:

48 Calculate the force between the electron & the nucleus of hydrogen: 4.0 x 10 -2 nm apart:

49 A BC d AB = 4.0 mm d BC = 3.0 mm q A = - 4.0 x 10 -5 C q B = 3.0 x 10 -5 C q C = 9.0 x 10 -5 C Calculate: F e on B

50 A BC d AB = 4.0 mm d BC = 3.0 mm q A = - 4.0 x 10 -5 C q B = 3.0 x 10 -5 C q C = 9.0 x 10 -5 C Calculate: F e on A

51 A BC d AB = 4.0 cm d BC = 3.0 cm q A = 3.0 x 10 -5 C q B = 3.0 x 10 -5 C q C = 6.0 x 10 -5 C Calculate: F e on C

52 Calculate the force between 2 particles 1.2 x 10 -3  m apart: q 1 = 4.0 x 10 -5 C q 2 = - 4.0 x 10 -5 C


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