1. Electricity and Electrical Charges
What is electricity?
All the phenomena caused by positive and negative charges.
Where do these charges come from?

2. Electrons: Nucleus: Located outside nucleus
Contains protons (+) & neutrons (no charge)
Overall positive charge (+)
Contains nearly all mass (dense)
Electrons:
Located outside nucleus
Easily moved, lost or gained
Negative charge (-)

3. Electrical Charges: - All matter has electrical charges
There are two types of charges:
Positive
Negative + -

4. Negatively charged objects: contain more electrons (-) than protons (+).
Positively charged objects: contain fewer electrons (-) than protons (+).
Only negatively charged electrons can move from one object to another and if you have an equal number of protons and electrons, the object is neutral.

5. Law of Charges Attraction Repulsion
There are 2 forces between charged objects:
Attraction
Repulsion
Opposite charges
“Opposites Attract”
Same charges
“Like repel”
Law of Charges

6. - + Ex #1 A B A POSITIVE Opposites Attract!
Sphere A is negatively charged.
When placed beside sphere B, they attract.
What is the charge on B?
POSITIVE
Opposites
Attract! A B A - +

7. - + + + - + Ex #2 Attract A C A B B C
Three charged spheres are suspended next to each other.
If sphere A is negatively charged, what will happen when sphere A & C are suspended beside each other?
Attract A C A B B C - + + + - +

8. + + + - - + Ex #3 A B B C C D Repel
Four charged spheres are suspended next to each other.
What will happen if A & D were suspended next to each other?
Repel A B B C C D + + + - - +

9. What would happen if “B” & “C” were brought together?
You have three charged objects – A, B & C in a lab. You record the following results:
Ex #4
Test
Observation
Bring “A” near “B”
They repel
Bring “A” near “C”
They attract + + + - + -
What would happen if “B” & “C” were brought together?
They would attract!!!

10. How do you measure “charge”
The unit of measure for electrical charge is the Coulomb (C). In equations it is symbolized by a “q”
Eg: q = 900C
One Coulomb is equal to the charge of 6.25 X 1018 electrons (-) or protons (+).

11. Charging Objects
Most objects start out electrically neutral, but by CHARGING an object you create an imbalance in the number of electrons and protons; the object is then charged and is either positive or negative.

12. How do you charge an object?
There are three ways to charge an object:
1. Charge by Friction
2. Charge by Conduction
3. Charge by Induction

13. Charging by Friction
When two neutral objects are rubbed against each other, one object may pull electrons away from the other creating one positive object and one negative object.

14. Triboelectric Series:
All objects begin neutral & can become positively or negatively charged
A positively charged object has more positives than negatives
A negatively charged object has more negatives than positives

15. Triboelectric Series:
Triboelectric series is a list that ranks objects’ ability to take negative charges
Rubber
Items at top
take negatives
Ebonite
Polyethylene
Cotton
Silk
Wool
Items at bottom
lose negatives
Glass
Acetate
Fur / Hair

16. Items at top
take negatives
Ex #1
Your cat rubs against a rubber balloon. What will be the charge on the balloon? Your cat’s fur?
Rubber balloon becomes negative
Rubber
Rubber Ebonite Polyethylene Cotton Silk Wool Glass Acetate Fur / Hair
Cat’s fur becomes positive
Fur / Hair
Negatives

17. Polyethylene balloon becomes negative
Items at top
take negatives
Ex #2
In a lab, you take a piece of neutral wool & neutral polyethylene & rub them together. What will be their charges?
Polyethylene balloon becomes negative
Rubber Ebonite Polyethylene Cotton Silk Wool Glass Acetate Fur / Hair
Polyethylene
Negatives
Wool
Wool becomes positive

18. In a lab, you rub a piece of cotton & ebonite together
In a lab, you rub a piece of cotton & ebonite together. Then you rub a piece of silk & glass together.
Ex #3
You then bring the charged piece of cotton & the charged piece of silk together. What will happen?
Rubber Ebonite Polyethylene Cotton Silk Wool Glass Acetate Fur / Hair -
Cotton is + Silk is - + -
They would ATTRACT +

19. Ex #4
You rub your hair with a balloon. Explain using words & pictures, why your hair “sticks up”.
1st Hair & balloon are both neutral _ + _ _ + +
2nd Rubber balloon takes negative charges from the hair. So, balloon becomes negatively charged & hair becomes positively charged + _ + _
3rd Since hair is positive & like charges repel, hair sticks up!!!

20. Charging by Conduction
An object can be charged by touching it with another object that already has a charge. The resulting object will then have the same charge but weaker in strength than the original object.
See figure 5.11 pg 145 in textbook

21. Charging by Conduction
This image shows how a positive charged object alters the charge on the globe via conduction.

22. Charging by Conduction
This image shows how a negative charged object alters the charge on the globe via conduction

23. Charging by Induction
Objects do not touch (one is charged, one is neutral)
Proximity of the charged object causes (induces) the charges in the neutral object to separate.
See Fig pg 147 in textbook.

24. Charging by Induction
This image shows how a negative charged object alters the charge on the globe via induction.

25. Charging by Induction
This image shows how a positive charged object alters the charge on the globe via induction.

26. Key Points to Remember
Two types of charges – positive (+) & negative (-)
“Opposites Attract”
“Like Repel”
Items at the top of the electrostatic series list take negative charges
Only negative charges move
Three methods to charge an object: friction, conduction, induction. These three methods are what cause static electricity.