1. Static Electricity Ms. Petrauskas

2. Static Electricity
An imbalance of electric charge on the surface of an object
Static means stationary or non-moving

3. Electric charge
A form of charge either positive or negative that exerts an electric force
Ex. When an atom is not neutral
A ‘+’ symbol represents a large number of protons an a ‘-’ symbol represents a large number of electrons
Shows the distribution of charges in an object

4. Law of Electric Charges
Like charges repel
Opposites attract
Any charge attracts neutral + + + -
+ - +

5. Laws continued
The strength of the electric force is directly related to the strength of the charges on each object
Decreases with distance between objects

6. Pithball electroscope
Detects charge
Pithball is neutral and if the object is charged then the pithball will be attracted to it.

7. Neutral Attraction
As a charged object is brought close to a neutral object it causes (induces) a rearranging of electrons
Inducing a movement of electrons is called induced charge separation
Charge not permanent!

8. Metal Leaf Electroscope
More sensitive than pith ball when detecting electrical charge
When a charge is transferred (by contact or by induction) the leaves receive the same charge and therefore repel each other

9. Charging by friction
When two objects of different materials rub against each other, they produce a net static charge

10. Electrostatic Charges
One material has a stronger attraction to electrons than another material, and therefore pulls those electrons away resulting in a negative charge
The material that loses electrons becomes positively charged
Most object are electrically neutral

11. Electrostatic Series
A list of materials arranged by their likelihood to attract electrons
Used to predict resulting charges from contact

12. Examples: see page 473
What is the resulting charge when ebonite and rabbit fur are rubbed together?
Nylon and wool?
Which would have a stronger resulting charge?

13. Insulators and Conductors
Insulator: electrons do not move freely between atoms in this material
Wood, rubber, wax
Conductor: electrons move freely from atom to atom in this material
Metal, tap water
Semi- conducter: electrons can move fairly well in these non-metal materials
Silicone, mixtures of arsenic, selenium and tellurium

14. Charging by Contact Aka charging by conduction
When two objects with different amounts of charge come into contact and electrons move from one object to another
“ electrons distribute”
The neutral object takes the charge of the charged object
SO when a + touches a neutral object the object become + and when - touches neutral it becomes -

15. Neutral Object becomes negative
Negatively charged

16. Neutral becomes positive

17. Grounding
Removing a net static charge by putting it into contact with the ground
Has a large number of electrons and can either supply or remove
Earth is so huge, it can do this without affecting its overall charge

18. Grounding = Neutralizes
Electrons move toward the earth
Electrons move up to neutralize

19. Shocks & Sparks
When a large number of electrons flow rapidly between objects (more often with a conductor)
Ex. When wearing cotton socks and you walk across a polyester carpet and then touch a doorknob= SHOCK!.
What charge do your socks become? Positive
When you touch a conductor like a doorknob, electrons quickly flow into you, to neutralize your charge, causing a shock or spark
Avoid by slowly releasing electrons with a insulator “ground”
Grounding is used in the following situations
Operating rooms
Fuel trucks
Lightning
Appliances

20. Applications Dryer sheets Higher humidity Grounding electronics
waxy coating equals charges so there is no transfer of electrons, no static
Higher humidity
more water in air and charges removed quickly through collisions because of the close proximity with water vapour
Grounding electronics
Third prong is a ground. Shocks and sparks can damage equipment and/or cause fires

21. Precipitator- remove pollution particles from air in power plants
Precipitator- remove pollution particles from air in power plants. Particles pass by negatively charged plates and become negative by contact. They then pass positive plates and stick.
Electrostatic duster- sweep across the ground, creates a build-up of charge, dust “jumps” from dusty surface to duster