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Do Now:

Do Now:. What does the word “charge” make you think of? What is the definition of the word “static”? Describe the parts and structure of an atom. Chapter 20. Static Electricity. Electrostatics. The study of charges that can be collected and held in one place.

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Do Now:

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  1. Do Now: What does the word “charge” make you think of? What is the definition of the word “static”? 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.

  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  qAqB

  29. Coulomb’s Law 1 d2 F 

  30. Coulomb’s Law qAqB d2 F 

  31. Fe Formula qAqB dAB2 Fe= k

  32. Electric Constant 9.0 x 109 Nm2 C2 k =

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

  34. Gravity Formula mAmB dAB2 Fg= G

  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 electrons8.0 x 10-3 nm apart:

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

  49. Calculate: Feon B A dAB = 4.0 mm dBC = 3.0 mm B C qA = - 4.0 x 10-5 C qB = 3.0 x 10-5 C qC = 9.0 x 10-5 C

  50. Calculate: Feon A A dAB = 4.0 mm dBC = 3.0 mm B C qA = - 4.0 x 10-5 C qB = 3.0 x 10-5 C qC = 9.0 x 10-5 C

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