1. It’s Electrifying!
E-Mag

2. Electrostatics Stored electricity, or electricity at rest
it involves the charges, forces between the charges and their behavior in various materials.

3. Electrical Forces Comes from particles within the atom
unlike charges cause attraction, like charges cause repulsion

4. Properties of Charge
The metric standard unit of charge is the coulomb (C).
It is equal to the charge of 6.24 x 1018 electrons
or the charge that passes through a 100 watt bulb in one sec.
Charge is always conserved!

5. Rub a balloon on your hair, the balloon attracts you hair
Rub a balloon on your hair, the balloon attracts you hair. Is the amount of charge in the balloon and your hair
A: more than before rubbing?
B: the same as before?
C: less than before?

6. The role that charge plays in electricity is similar to the role of mass when dealing with gravity.
As charge increases or distance between objects decreases, the force of attraction increases.

7. Electrostatic Force
Coulomb’s law -- the force (either attraction or repulsion) between two charged particles is a function of the amount of charge on each particle and the distance between them.

8. Coulomb’s Law
Calculated very similarly to Force, using Newton’s gravitational constant.
K = Nm2/C2 or 8.99 x 109 Nm2/C2

9. Like gravity, electrostatic force is an inverse square function.
What has more effect on the force, amount of charge or distance? How do you know?

10. Think about it
Recall the value of G from Newton’s law of universal gravitation and compare it to the value of k (Coulomb’s constant).
Which is stronger, gravity or electrical force?
Explain!

11. Attraction/Repulsion
If an electron at distance X from a charged particle is attracted with force X, how big is the force at distance 2X?
Is the charged particle positive or negative?

12. Coulomb’s Law simplified

13. q is the symbol used to represent charge, while n is a positive or negative integer, and e is the electronic charge, 1.60 x Coulombs.

14. “Watts” of Force!

15. Conductors allow charges to flow through them easily
electrons are not tightly anchored to the nucleus

16. Electrical Conductor
Not this kind of conductor!

17. Insulators
Electrons are tightly bound to the nucleus and cannot easily move.
Charges cannot easily flow through them.
Ex: plastic, styrofoam

18. Different Types of Material
Within a conductor charge can move freely
Charges in insulators do not move [much]
Conducting properties vary dramatically in semi-conductors depending on impurities and charge present

19. Static Electricity
A build up of electric charges in an object or in an area of an object.
Rubbing your feet on the carpet so that you can “shock” someone
Phet simulation:
4.5 min, video:

20. How Do Refueling Fires Happen?
Static charge picked up when re-entering vehicle
Touching nozzle without discharging static electricity
A spark ignites fumes
Static electricity flash fires at gasoline stations are more common than they used to be. The percentage of fires is small, (there are approximately 12 billion fill-ups annually and perhaps 15 or 20 flash fires that are reported each year) but they can be catastrophic. Most of the fires occur November through February when the air is cooler and drier, but they can happen any time of the year. As of March 2004, thirty-nine states had reported fires to the Petroleum Equipment Institute (PEI).
When a person first gets out of the vehicle at a gas station, he/she may close the car door, touch the pay-at-the-pump area, open the fill pipe cover on their vehicle, remove the cap, and touch the gas pump nozzle and the octane pad – any or all of those instances of touching metal will discharge the static electricity buildup the person may have accumulated from being in the vehicle.
When a person re-enters the vehicle, there is contact between the person’s clothing and the car seat. This is where a static charge can be picked up. If the person gets out of the car but doesn’t touch metal before touching the nozzle again, there can be a static spark that will ignite the fumes and cause a flash fire.
Show video of flash fires.

21. Fires are reported to the Petroleum Equipment Institute Web site
How Often Do They Occur?
Fires are reported to the Petroleum Equipment Institute Web site
Most static fires have been reported since 1998
No one knows how many – 175 have been reported since 1992
The Petroleum Equipment Institute (PEI) has a report form on its Web site. People have to know to report the fire to PEI. The first static electricity gasoline fire reported was in About 175 have been reported, most since No one knows how many there actually are. The industry feels that the problem isn’t going away. The fires continue to occur.

22. Three Causes of Static Fires
50% happen when the refueler returns to the vehicle during refueling and doesn’t shut the car door
29% happen when the refueler unscrews the gas cap
21% happen for unknown reasons
When the refueler returns to the car during the refueling process, he/she can pick up a static charge from coming in contact with the seat material. Often the person doesn’t close the door, then slides out of the car without touching anything. As a result, any static buildup that occurs isn’t discharged because the person hasn’t touched anything that is metal.
Flash fires that erupt as the refueler first unscrews the gas cap may occur when there is a lever inside the car to release the cover over the fuel intake area. The refueler goes directly to remove the cap without discharging the static first, causing a flash. There is no additional fire, since there is no fuel going into the fill pipe.
Something else happens – the causes of these static electricity fires haven’t been determined. The source of ignition isn’t known.

23. More Safety Guidelines
DO NOT get back into your car when refueling
DO NOT top off your tank
If a flash fire occurs, back away, contact attendant, and most important:
LEAVE NOZZLE IN VEHICLE!
If you must get back into your car during the refueling process, be sure to discharge static buildup when you exit the vehicle by touching metal away from the refueling area. When you first get out of your car at a gas station, you probably touch the door, the pump, the cover over the fill pipe, the credit card area on the pump, and the nozzle handle. Consequently, the static is discharged before you begin pumping fuel into the tank.
Do not top off your tank. As gasoline warms, it expands. Without an air space available, expansion can force liquid out of the tank.
In the unlikely event of a flash fire, leave the nozzle in the vehicle and contact the attendant. If the nozzle is pulled out without turning off the fuel, the flames will follow the gas and cause much more serious damage and possible injury. Damage and injury are more likely to occur when the nozzle is removed from the vehicle.

24. Charging by Friction
Transfer of electrons by friction between two objects
rubbing a balloon so that it will “stick” to a wall
Travolta simulation:

25. Charging by Direct Contact
Conduction… transfer of electrons when one object touches another.
touching someone and “shocking” them

26. Charging by Induction
Transfer of electrons when objects are brought near each other, but do NOT touch.

27. How does Lightning start and end?

28. Induction: Balloon on wall Wall is neutral and an insulator
+ move slightly towards balloon
- move slightly away from balloon
Wall is neutral but has small surface charge, sufficient to hold balloon

29. Induction to Charge Object

30. Van De Graaff Generator
Robert Jemison Van de Graaff invented the Van de Graaff generator in 1931.
The device has the ability to produce extremely high voltages -- as high as 20 million volts.

31. 1) hollow metallic sphere (with positive charges) 2) electrode connected to the sphere, a mesh in close proximity (but not contacting) the electrode and the belt 3) upper roller
4) side of the belt with positive charges 5) opposite side of the belt with negative charges 6) lower roller (metal) 7) lower electrode (ground) 8) spherical device with negative charges, used to discharge the main sphere 9) spark produced by the difference of potentials

32. Electroscope
When a negatively charged object is close to another object, electrons will be repelled from the first object.
Therefore, that end will have a negative charge. This process is called charging by induction.  

33. When a negatively charged object touches a neutral body, electrons will spread on both objects and make both objects negatively charged. This process is called charging by conduction.
What happens if you touch the top of the electroscope?

34. Electric Fields
The space around every electric charge. This is similar to the gravitational field located around every mass.
Vectors point away from a positive test charge and toward a negative test charge.
Field line simulation:

35. Field Lines