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.

Chapter 20 Static Electricity

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

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

Charge Caused by an electron imbalance as electrons move

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

Charge Opposite charges attract & like charges repel

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

Millikens Oil Droplet Experiment

Electron Charge 1.60 x C C = Coulombs

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

Charge Charged objects eventually return to their neutral state

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

Conductors Materials like metals that allow electrons or charges to move

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

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

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

Electron Sink Anything that can absorb lots of electrons

Common Electron Sinks People, Earth, etc

Electroscope A device used to detect electrical charge

Charge Redistribution Conduction Induction

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

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

Charge Separation on Neutral Objects

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

Electrical Force Force caused by the attraction or repulsion of charges

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

Coulomb’s Law F  q A q B

Coulomb’s Law F  1d21d2

Coulomb’s Law F  q A q B d 2

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

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

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

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

Electrical Force Electrical force must be much greater than gravitational force

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

Subatomic Particles 9/2/2011

Subatomic particle masses Electron: x kg Proton: x kg Neutron: x kg

Review: Electron Charge 1.60 x C C = Coulombs

Elementary charge e = 1.60 x C

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

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

Do Now: On half-sheet of paper

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

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

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

Calculate the force between 2 electrons 8.0 x nm apart:

Calculate the force between the electron & the nucleus of hydrogen: 4.0 x nm apart:

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

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

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

Calculate the force between 2 particles 1.2 x  m apart: q 1 = 4.0 x C q 2 = x C