Do Now (8/26/13):

Welcome!

1.Find your seat

2.Write your name on the notecard on your desk.

Brainstorm:

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 20Static

Electricity

Intro

• Syllabus

• Course outline

• BPI webpage

• Vocab

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.

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 (8/27/13):

• Complete the pre-lab

Do Now (8/28/13):

• Complete the Drill sheet

Electrical Force•Force caused by the

attraction or repulsion of charges

Electrical Force•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

F 1d2

Coulomb’s Law

F qAqB

d2

Fe Formula

Fe = KqAqB

dAB2

Electric Constant

K = 9.0 x 109 Nm2

C2

Identify another formula that is very

similar to the electrical force

formula

Gravity Formula

Fg = GmAmB

dAB2

The magnitude of the force is inversely proportional to the square of the distance

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

Electron Charge

1.60 x 10-19 CC = Coulombs

Calculate the force between 2 electrons8.0 x 10-3 nm apart:

Calculate the force between the electron

& the nucleus of hydrogen:

4.0 x 10-2 nm apart:

Do Now (8/29/13):

• Complete the Drill sheet

Do Now (8/30/13):

• Complete the Drill sheet

A

B C

dAB = 4.0 mmdBC = 3.0 mm

qA = - 4.0 x 10-5 CqB = 3.0 x 10-5 CqC = 9.0 x 10-5 C

Calculate: Fe on B

A

B C

dAB = 4.0 mmdBC = 3.0 mm

qA = - 4.0 x 10-5 CqB = 3.0 x 10-5 CqC = 9.0 x 10-5 C

Calculate: Fe on A

A

B C

dAB = 4.0 cmdBC = 3.0 cm

qA = 3.0 x 10-5 CqB = 3.0 x 10-5 CqC = 6.0 x 10-5 C

Calculate: Fe on C

Calculate the force between 2 particles1.2 x 10-3 m apart:

q1 = 4.0 x 10-5Cq2 = - 4.0 x 10-5C