1. STATIC ELECTRICITY: A Particle Model of Electricity

2. Neutral Conservation of Charge Insulator Conductor Polarization
OUTCOME QUESTION(S):
S1-3-04:
How does the Atomic Model help to explain static electricity?
Vocabulary & Concepts 
Neutral Conservation of Charge
Insulator Conductor
Polarization

3. Study of static electricity – static means “at rest.”
Electrostatics:
Study of static electricity – static means “at rest.”
Electricity that is localized, not moving
Greek Philosophers noted:
Amber rubbed with fur attracts bits of paper / dust.
Electric, electricity and electron all come from the Greek word for amber - elektron

4. Knew electric charge came from a transfer of invisible SOMETHING
Benjamin Franklin (1750)
Experimented with friction; causes objects to repel or attract materials – “charged”
Atoms (and subatomic particles) were not discovered yet
– try explaining electricity without electrons…?
Knew electric charge came from a transfer of invisible SOMETHING
First to use words “positive” and “negative” as description

5. Atoms contain 3 subatomic particles (1890)
Neutron – stationary particle with no charge (nucleus)
Proton – stationary particle with a positive charge (nucleus)
Electron – moving particle with a negative charge (orbits)
All atoms start off neutral: no net electric charge
Friction (rubbing) provides enough energy to cause electrons to transfer between materials
We now KNOW:

6. + + + + - - - + + - + - Charged Objects + - + - + - Neutral Object
- + -
Neutral
Object
+ + +
- + +
+ - -
- + -
Positively Charged
Object
Negatively Charged
Object

7. Negative and positive static charges result from the addition and removal of electrons ONLY
(-)
(+)

8. Particle Model of Electricity
- Three states of charge exist : (+), (-) and neutral.
- Neutral objects are charged by friction.
(movement of electrons)
Static: an excess or lack of electrons on a material.
- Creates forces of attraction and repulsion
(+) and (-)
(-) and (-) OR (+) and (+)
Conservation of Charge:
Since no new particles are created (Conservation of Matter)
the total number of (+)/(-) stay the same always.

9. Notice the Conservation of Charge – after the transfer of electrons the net charge (together) still adds to zero

10. +++ + - - - - Most Positive (+) Most Negative (-)
When rubbed together, materials have a different strength of attraction for the electrons
Most Positive (+)
Human Skin
+++  +
Fur
Glass
Human Hair
Wool
Silk
Paper
Cotton
Rubber -
- - -
Copper
Silver
Polyester
Plastic
Most Negative (-)
Easily lose electrons
Easily gain electrons

11. In order to build a charge, we need to move Electrons!
So…how do we move Electrons?
1. Conduction: electrons are transferred by direct contact.
2. Induction: electrons on an object are rearranged without physical contact.

12. Induction
Rod with negative charge

13. Induction Rod with negative charge
Pushes electrons in electroscope down

14. Induction Rod with negative charge
Pushes electrons in electroscope down
Extra negative charge

15. Induction Rod with negative charge
Pushes electrons in electroscope down
Extra negative charge
Leaves move apart

16. Induction
Remove rod everything returns

17. Conduction
Rod with negative charge

18. Conduction
Rod with negative charge

19. Conduction
Rod with negative charge
Transfers electrons

20. Conduction Rod with negative charge Transfers electrons
Extra negative charge

21. Conduction Rod with negative charge Transfers electrons
Extra negative charge Moves leaves apart.

22. Electrical charge is localized - fixed Electrons can’t move around
Since static electricity is stationary charge (stays put) only some materials can maintain a charge
Consider which balloon you can charge by rubbing on your hair and have stick to a wall
Insulators:
Electrical charge is localized - fixed
Electrons can’t move around
Rubber, plastic, cloth, glass, wood
Conductors:
Electrical charge spreads through material
Electrons move around, weakening charge
Most metals are good conductors _ _ _ _ _ _ _ _ _ _ _ _

23. Electrons repel – polarization of paper atoms
Charged objects attract a neutral object by inducing electrons to move over to one side:
Polarization – separation of charges within a neutral material creating (+) and (-) areas
Neutral object
Causes Attraction!
(-) charged object
Electrons repel – polarization of paper atoms

24. Electrons attract – polarization of paper atoms+ + + +
Neutral object + + +
Causes Attraction!
(+) charged object
Electrons attract – polarization of paper atoms
This separation of charges explains why neutral objects attract to both (+) and (-) charged objects

25. Static discharge Eventually static electric charge will move.
Slowly the electrons may move into moisture in the air
Or quickly in a spark.

26. What Causes Lightning?
Lightning is actually just static electricity on a much larger scale.
The rubbing is caused by air moving around
In thunderclouds bottom is usually negative and top is positive.

29. Lightning is (-) charge in the clouds causing polarization in the surface of the Earth followed by a shock of electrons between the two

30. CAN YOU ANSWER THESE QUESTIONS? S1-3-04:
How does the Atomic Model help to explain static electricity?
Vocabulary & Concepts 
Neutral Conservation of Charge
Insulator Conductor
Polarization