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Published byBrian Nash Modified over 9 years ago
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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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Chapter 20 Static Electricity
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Electrostatics The study of charges that can be collected and held in one place
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With your “elbow partner” come up with examples where charge differences build up in nature, and describe the consequences
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Charge Caused by an electron imbalance as electrons move
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Atomic Charge In neutral atoms the number of electrons = the number of protons
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Charge Opposite charges attract & like charges repel
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charge conservation: electric charge can neither be created nor destroyed. electric charge
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Millikens Oil Droplet Experiment
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Electron Charge 1.60 x 10 -19 C C = Coulombs
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Charge The charge of an object leaks off into water molecules in air
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Charge Charged objects eventually return to their neutral state
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Charge Holding a charge is easy on dry days & difficult on humid days
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Conductors Materials like metals that allow electrons or charges to move
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Common Conductors Copper, silver, gold, aluminum, & graphite
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Insulators Materials that will not allow electrons or charges to move easily
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Common Insulators Glass, dry wood, plastic, rubber, & dry air
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Electron Sink Anything that can absorb lots of electrons
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Common Electron Sinks People, Earth, etc
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Electroscope A device used to detect electrical charge
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Charge Redistribution Conduction Induction
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Charge by Conduction Charge by touching a charged body to a neutral body
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Charge by Induction Charge by moving a charged body near a neutral body
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Charge Separation on Neutral Objects - - - + - - - + - - - + - + - + - + + + - + + + - + + +
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Do Now (9/1/11): On half- sheet of paper: #5 is True
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Electrical Force Force caused by the attraction or repulsion of charges
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Coulomb’s Law Force between charges is proportional to charge & inversely proportional to distance between charges
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Coulomb’s Law F q A q B
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Coulomb’s Law F 1d21d2
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Coulomb’s Law F q A q B d 2
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F e Formula F e = k q A q B d AB 2
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Electric Constant k = 9.0 x 10 9 Nm 2 C 2
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Identify another formula that is very similar to the electrical force formula
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Gravity Formula F g = G m A m B d AB 2
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Electrical Force Electrical force must be much greater than gravitational force
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Do Now (9/2): Complete the half-sheet of paper on your desk. Leave #1 and 2 blank
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Subatomic Particles 9/2/2011
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Subatomic particle masses Electron: 9.1093 x10 -31 kg Proton: 1.6726 x 10 -27 kg Neutron: 1.6749 x 10 -27 kg
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Review: Electron Charge 1.60 x 10 -19 C C = Coulombs
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Elementary charge e = 1.60 x 10 -19 C
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Subatomic Particle Charges Electron: -e Proton: e Neutron: 0
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Working with Coulomb’s Law Algebraically Given q in terms of other q q’s are equal to
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Do Now: On half-sheet of paper
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Agenda: Homework questions – 5- 10 min Quiz – 10 – 15 min Work on homework – rest of class
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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:
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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:
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Calculate the force between 2 electrons 8.0 x 10 -3 nm apart:
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Calculate the force between the electron & the nucleus of hydrogen: 4.0 x 10 -2 nm apart:
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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
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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
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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
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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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