1. Static Electricity

2. What is Static Electricity
The buildup of electrical charges in one place.
Static = charge does not move or flow
(usually a temporary condition).
Can be detected by an electroscope.

3. Examples of static electricity:
Rubbing a balloon on your hair
Walking across carpet
Clothes tumbling in dryer
What do these have in common?
Friction!!!!

4. Creating Static Charges
Static charges result when some charges are transferred from one object to another by friction
Which charges are easily removed?
Recall structure of the atom.

5. Recall from Chemistry
Electrons (-) are on the outside of the atom so they can be easily removed, while protons (+) are held firmly in the nucleus
Protons & Neutrons
Electrons

6. Two Types of Charge
Electrons can be transferred by friction, but protons cannot
Transferring protons would create a new element!
LOSING electrons gives an object a POSITIVE charge
GAINING electrons gives an object a NEGATIVE charge
NOTE: When one object loses, another must gain - electrons can’t be created or destroyed

7. BEFORE
Combing transfers electrons from the hair to the comb by friction, resulting in a negative charge on the comb and a positive charge on the hair.
AFTER

8. Induced charge
Charged and neutral objects (not touching) are attracted because electrons move in the neutral object.
Electrons move toward a +ve charged object and away from a –ve charged one.
This is called “induced charge”

9. Conduction Conduction = direct transfer of charge
Eg: walk across carpet and touch a doorknob  shocking!
Electrons are stripped from the carpet and you gain a net –ve charge
When you touch the doorknob, electrons jump onto it  electrical discharge

11. Attract Repel Neither Place an “X” in the appropriate box: +ve and -ve
+ve and neutral
+ve and +ve
-ve and neutral
-ve and –ve
Neutral and neutral

12. Attract Repel Neither X Place an “X” in the appropriate box:
+ve and -ve X
+ve and neutral
+ve and +ve
-ve and neutral
-ve and –ve
Neutral and neutral

13. Rules of static electricity
Objects with like charges repel, but objects with unlike charges attract
Charged objects attract neutral objects

14. Does friction always create static charge?
Different materials have different strength of attraction for electrons
If two objects of the same material are rubbed, no static charge forms
(equal number of electrons transfer each way)

15. If two different objects are rubbed, they have different attractions to the e-
The stronger one will take e- away from weaker one and static charges build up

16. Uses of static electricity
Trapping particles in smokestacks of factories
Applying grit to sandpaper
Spray painting mesh (e.g. chain link fence)
Powder coating

17. The leaves are repelled by the like charge upon them.

18. 7.2 Electric Force--Summary
Force is a push or pull - electric force can do both, without touching the object - it is an action-at-a-distance force.
Laws of Static Charge
Like charges repel
Opposite charges attract
Neutral objects are attracted to charged objects
See pages

19. Charging Objects Charging By Conduction Charging By Induction
Charging through direct contact
Extra electrons will move to a location where there is less of them
Charging By Induction
Bringing a charged object nearby a neutral object will cause charge movement and separation in the in the neutral object
(like charges repel!)
See pages