2. Static Electricity
• What is Electricity ?
• What is Static Electricity
?
• difference between them ?
3. Static Electricity
• What is Electricity
Electricity is a form of energy. Electricity is the flow of electrons.
All matter is made up of atoms, and an atom has a center, called a
nucleus. The nucleus contains positively charged particles called
protons and uncharged particles called neutron
+
+
+
–
––
Atom Nucleus
4. Static Electricity
• What is Static Electricity
Static electricity occurs when there is a build up of electric
charge on the surface of a material.
It is called static electricity because the charges don’t move.
The electricity we use everyday involves moving charges.
Static = Charge does not move or flow
5. 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
Static Electricity
6. Static Electricity
Where do charges come from?.
If electrons = protons ⇒ neutral
If electrons > protons ⇒ gaining electrons, negative charge
If electrons < protons ⇒ losing electrons, positive charge
7. Static Electricity
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.
The balloon: – charged,
The wool: +chargedwool
– +
+
+
+
+
–
–
–
–
–
8. Static Electricity
Where do charges come from?
Rubbing materials does NOT create
electric charges.
It just transfers electrons from one
material to the other.
9. Static Electricity
Examples of static electricity:
Rubbing a balloon on your hair
Walking across carpet
Clothes tumbling in dryer
What do these have in common?
Friction!!!!
11. Static Electricity
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”
12. Static Electricity
Conduction
Conduction = direct transfer of charge
Example : walk across carpet and touch a doorknob shocking!
Electrons are stripped from the carpet and we gain a –ve charge
When you touch the doorknob, electrons jump onto it :
electrical discharge
13. Static Electricity
Rules of static electricity
Objects with like (same) charges repel, but
objects with unlike charges attract.
Charged objects attract neutral objects
14. Static Electricity
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)
If two different objects are rubbed, they will have different
attraction to the electrons. The stronger one will take electrons
away from weaker one and static charges build up
15. Static Electricity
Uses of static electricity
Dust removal (Pollution Control)
Photocopy (Xerography)
Car Painting
16. Static Electricity
Effect of Materials on Static Electricity
Materials are listed below according how well they create static electricity
when rubbed with another material, as well as what charge the material
will possess.
Become positive in charge
Materials that gain a positive (+) electrical charge ( or tend to give up
electrons)
Dry human skin Greatest tendency to giving up electrons and
becoming highly positive (+) in charge
Leather
Glass The glass on your TV screen gets charged and
collects dust
17. Static Electricity
Effect of Materials on Static Electricity
Human hair "Flyaway hair" is a good example of having a moderate
positive (+) charge
Nylon
Wool
Lead A surprise that lead would collect as much static
electricity as cat fur
Cat fur
Silk
Aluminium Gives up some electrons
Paper
18. Static Electricity
Effect of Materials on Static Electricity
Neutral
There are very few materials that do not tend to readily attract or give up
electrons when brought in contact or rubbed with other materials.
Materials that are relatively neutral
Cotton Best for non-static clothes
Steel Not useful for static electricity
19. Static Electricity
Effect of Materials on Static Electricity
Become negative in charge
Materials that gain a negative (−) electrical charge
Wood Attracts some electrons, but is almost neutral
Nickel, Copper Copper brushes used in Wimshurst electrostatic generator
Gold, Platinum Attract electrons almost as much as polyester
Polyethylene
(Scotch Tape)
Pull Scotch Tape off surface and it will become charged
