1. Static Electricity

2. What Is Static Electricity?
A stationary electrical charge that is built up on the surface of a material

3. Where do charges come from?
Matter is made up of atoms. + –
Proton (positive charge) +
neutron (neutral)
electron (negative charge) –
atom
nucleus

4. Where do charges come from?
If electrons = protons neutral
If electrons > protons  gaining electrons, negative charge
If electrons < protons  losing electrons, positive charge

5. Law of Electric Charges
The law of electric charges states that like charges repel, and opposite charges attract.
Protons are positively charged and electrons are negatively charged, so they are attracted to each other.
Without this attraction, electrons would not be held in atoms.

6. Electro-negativity + + + + + + + + + + + + electro-negativity + +
- -
- - -
Glass
Human Hair
Nylon
Silk
Fur
Aluminum
Paper
Cotton
Copper
Rubber
PVC
Teflon
Relative
electro-negativity
ranking for some
common materials
from electron donating
materials (+, glass) to
electron accepting
materials (-, teflon)

7. Electric Force The force between the charged objects is an
The size of the electric force depends on 2 things:
The amount of charge (the greater the charge, the greater the force)
The distance between charges (the further the distance, the less the force)

8. Insulators and conductors
Insulators: materials that do NOT allow electrons to flow through them easily.
Insulators can be easily charged by friction as the extra electrons gained CANNOT easily escape.

9. Insulators and conductors
Conductors: materials that allow electrons to flow through them easily.
Conductors CANNOT be easily charged by friction as the extra electrons gained can easily escape.

10. How Can You Charge Objects?
There are 3 ways objects can be charged:
Friction
Induction
Conduction

11. Where do charges come from?
Rubbing materials does NOT create electric charges. It just transfers electrons from one material to the other.

12. Where do charges come from?
When a balloon rubs a piece of wool...
electrons are pulled from the wool to the balloon. + – –
The balloon has more electrons than usual.
wool
The balloon: – charged,
The wool: +charged

13. Two kinds of charges
After being rubbed, a plastic ruler can attract paper scraps.
Ruler carries electric charge.
It exerts electric force on paper.
This charging method is called charging by friction.
The interaction between static electric charges is called electrostatics.

14. Induction: The production of a charge in an uncharged body by bringing a charged object close to it
When negatively charged rod is put near a metal can...
electrons of the can are pushed away from the rod. -
induced charges
 top of the can: positive
attraction +
buttom of the can: negative
& attraction > repulsion -
metal can
repulsion

15. Attraction of uncharged objects
Similarly, when charged rod is close to paper scrap...
molecules of paper align. -
 attraction between the rod and + charge > repulsion between the rod and - charge.
attraction + –
paper
repulsion

16. Conduction
Charging by conduction happens when electrons move from one object to another through direct contact (touching).
Ex. Suppose you touch an uncharged piece of metal with a positively charged glass rod. Electrons from the metal will move to the glass rod. The metal loses electrons and becomes positively charged. 

17. Electricity
Static

18. Static Discharge
Human body can not feel less than 2,000 volts of static discharge
Static charge built up by scuffing shoes on a carpet can exceed 20,000 volts?

20. Grounding What is grounding?
An object is grounded when it is connected to the earth through a connecting wire.
If a charged conductor is grounded, it will become neutral.

21. Grounding b How does grounding occur?
When we touch a metal ball of positive charge... + +
electrons flow from the earth to the metal ball to neutralize the metal ball. + + + –
Metal ball becomes neutral.

22. Grounding How does grounding occur?
Similarly, if the metal ball is of negative charge... – –
extra electrons flow from the metal ball to the earth and the ball becomes neutral. – – – –

23. Lightning kills more than 60 people and
injures more than 400 people a year in the US
one mile every five seconds
about 20,000 C
Voltage of up to 1.2x108 volts

25. How Lightning Forms