Chapter 20 Static Electricity

Calculate: 6.4 x 10274 x 1.5 x 10-162  8.0 x 10-254  7.5 x 10175 x 2.0 x 10-225 =

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

Come up with examples where charge differences build up in nature, and describe the consequences

Caused by an electron imbalance as electrons move Charge Caused by an electron imbalance as electrons move

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

Opposite charges attract & like charges repel

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

Charged objects eventually return to their neutral state

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

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

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

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

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

Anything that can absorb lots of electrons Electron Sink Anything that can absorb lots of electrons

Common Electron Sinks People, Earth, etc

A device used to detect electrical charge Electroscope A device used to detect electrical charge

Define: Conductor Insulator Electron Sink

Charge Redistribution Conduction Induction

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

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

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

- - - + - - - + - - - + - + - + - + + + - + + + - + + + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

- - - + - - - + - - - + - + - + - + + + - + + + - + + + + + + -+ + +-+ + +-+ - + - + - + - - - + - - - + - - -

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

Electrical force must be much greater than gravitational force

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

Coulomb’s Law F  qAqB

Coulomb’s Law 1 d2 F 

Coulomb’s Law qAqB d2 F 

Fe Formula qAqB dAB2 Fe = K

Electric Constant 9.0 x 109 Nm2 C2 K =

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

Define: Charge by Induction Charge by Conduction

Gravity Formula mAmB dAB2 Fg = G

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:

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:

Millikens Oil Droplet Experiment

+ plate Fup Fup = Fdown Fdown qoqp d2 m1m2 d2 Fdown = G = mg Fup = K

qoqp d2 K = mg mgd2 Kqp qo =

Electron Charge 1.60 x 10-19 C C = Coulombs

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

Calculate the force between the electron & the nucleus of hydrogen: 4 Calculate the force between the electron & the nucleus of hydrogen: 4.0 x 10-2 nm apart:

Calculate: Fe on B dAB = 4.0 mm dBC = 3.0 mm qA = - 4.0 x 10-5 C qB = 3.0 x 10-5 C qC = 9.0 x 10-5 C

Calculate the force between 2 particles 1.2 x 10-3 mm apart: q1 = 4.0 x 10-5C q2 = - 4.0 x 10-4C

Calculate: Fe on A dAB = 4.0 mm dBC = 3.0 mm qA = - 4.0 x 10-5 C qB = 3.0 x 10-5 C qC = 9.0 x 10-5 C

Calculate: Fe on C dAB = 4.0 mm dBC = 3.0 mm qA = -4.0 x 10-2 C qB = 3.0 x 10-2 C qC = 6.0 x 10-2 C

Calculate the charge of a particle 3 Calculate the charge of a particle 3.0 mm away from a magnet that can produce a force of 300.0 N with a charge of 0.020 C.

Calculate: Fe on B dAB = 5.0 mm dBC = 10.0 mm qA = -4.0 x 10-3 C qB = 3.0 x 10-3 C qC = 6.0 x 10-3 C C

Explain, on the atomic level, how any substance can build up an electric charge.

Calculate: Fe on C dAC = 5.0 nm dBC = 3.0 nm qA = 4.0 x 10-3 C qB = 3.0 x 10-3 C qC = 5.0 x 10-3 C

Calculate: Fe on B dAB = 6.0 nm dBC = 5.0 nm qA = 4.0 x 10-3 C g B C qA = 4.0 x 10-3 C = 44o = 37o = 40o Small = 30o qB = 3.0 x 10-3 C qC = 5.0 x 10-3 C

Explain how to attain a charge & the conditions necessary for attaining that charge.