1. Static Electricity
Created by Craig Smiley (Harrison HS, West Lafayette, IN)
Supported by grant PHY
from the National Science Foundation
and by Purdue University

2. Lesson 1 – Ways of Charging

3. Interaction of Charged Objects
A neutral object made of a conductive material is by itself, and the model of the arrangement of electrons and protons in the crystal lattice looks like this.

4. Interaction of Charged Objects
If a negatively charged object was brought near the neutral object made of a conductive material, what would it look like?

5. Interaction of Charged Objects
If a negatively charged object was brought near the neutral object made of a conductive material, what would it look like? A. B. C. D.

6. Interaction of Charged Objects
If a negatively charged object was brought near a neutral object made of an insulative material, what would it look like? A. B. C. D.

7. Interaction of Charged Objects
Will a neutral object be attracted to a positively charged object that is brought close to it?
Yes
No, it will repel
No, it will do nothing
Depends on the material

8. Interaction of Charged Objects
Two socks are taken out of the dryer and they stick together due to static cling. Which of the following statement(s) describe(s) why this occurs?
The socks have the same type of charge
The socks have opposite type of charges
One sock is positively charged and the other is neutral
One sock is negatively charged and the other is neutral
A, C, and D are possibilities
B, C, and D are possibilities

9. Charging by Friction
If you charged a metal sphere by friction, where on the sphere would it be charged?
Throughout the entire volume of the sphere and the charge would be equally dispersed.
Throughout the entire volume of the sphere but the charge would be more concentrated where it was rubbed.
Over the entire surface area of the sphere (nothing in the middle) and the charge would be equally dispersed.
Over the entire surface area of the sphere (nothing in the middle) but the charge would be more concentrated where it was rubbed.
Only where it was rubbed.
Depends if it was positively or negatively charged.

10. Charging by Friction
If you charged a rubber sphere by friction, where on the sphere would it be charged?
Throughout the entire volume of the sphere and the charge would be equally dispersed.
Throughout the entire volume of the sphere but the charge would be more concentrated where it was rubbed.
Over the entire surface area of the sphere (nothing in the middle) and the charge would be equally dispersed.
Over the entire surface area of the sphere (nothing in the middle) but the charge would be more concentrated where it was rubbed.
Only where it was rubbed
Depends if it was positively or negatively charged.

11. Charging by Conduction
What happens when a positively charged object touches a neutral conductor?
Extra protons from the charged object jump over to the neutral conductor making the conductor positively charged.
Electrons from the positively charged object jump over to the neutral conductor making the conductor negatively charged.
Electrons from the neutral conductor jump over to the positively charged object making the conductor positively charged.
The charged particles polarize, but the conductor does not become charged.
None of these

12. Charging by Induction
What happens when a neutral conductor is charged by induction by a negatively charged object?
Electrons from the charged object jump over to the neutral conductor making the conductor negatively charged.
Electrons from the neutral conductor jump over to the charged object making the conductor positively charged.
Electrons from the conductor go to ground leaving the conductor positively charged.
Electrons from the ground go to the conductor making it negatively charged.
Protons from the ground go to the conductor making it positively charged.

13. Charging by Induction
You are standing under an thundercloud, which has strong negative charge. You touch a metal fence post with your knee and experience a little shock. Assuming the fence post was neutral b/c it is in the ground and your feet are not in contact with the ground b/c you are wearing tennis shoes, what is the charge on you after the shock?
Positive
Negative
Neutral
Can’t be determined

14. Coke can & rubber rod After hmwk: VdG gen & hair
Lesson 2 – Coulomb’s Law
Coke can & rubber rod
After hmwk: VdG gen & hair

15. Charge on an object
What does it mean if an object has a charge of -1C ?
It has 1 electron
It has 1 more electron than it has protons
It has 6.25x1018 electrons
It has 6.25x1018 more electron than it has protons
None of these

16. Charge on an object
In chemistry you would say that Magnesium (Mg) would like to lose two electrons to be stable, which could be written like Mg+2 How many Coulombs of charge would that be on the Magnesium atom?
+2C
+2μC
+1.25x10-18 C
Can’t be determined

17. Coulomb’s Law
Two equal packaging peanuts are charged, and hang on strings as shown. What can you conclude about the signs of the charges q1 and q2 on the two packaging peanuts?
Both are +
Both are –
One is + and the other is –
Both must be the same charge (but if they are both + or both – can’t be determined)
Can’t be determined

18. Newton’s 3rd Law Which is experiencing a greater gravitational force?
Earth
Moon
The same

19. Coulomb’s Law
Two identical uniformly charged spheres, and the charge on sphere 2 is three times the charge on sphere 1. Which force diagram correctly shows the magnitude and direction of the electrostatic forces? A. B. C. D. E.

20. Coulomb’s Law
Two equal packaging peanuts are charged, and hang on strings as shown. What can you say about the magnitudes of the charges q1 and q2 on the two packaging peanuts?
q1 = q2
q1 ≠ q2
Can’t be determined

21. Coulomb’s Law
There are three charged objects in a line that indicate the sign of their charges but not their magnitudes. The net force on charged object 2 is directed to the:
Right
Left
Can’t be determined

22. Coulomb’s Law
There are three charged objects in a line that indicate the sign of their charges but not their magnitudes. The net force on charged object 3 is directed to the:
Right
Left
Can’t be determined

23. Coulomb’s Law
There are three charged objects in a line that indicate the sign of their charges but not their magnitudes. The net force on charged object 1 is directed to the:
Right
Left
Can’t be determined

24. Coulomb’s Law
Object A has a charge of +4C and is near Object B, which has a charge of -3C. Object B is then replaced with Object C, which has a charge of +6C. What happened to the electrical force on Object A?
Doubled and same direction
Doubled and opposite direction
Tripled and opposite direction
Quadrupled and same direction
E. None of these A B C A

25. Coulomb’s Law
Two charged objects are a certain distance apart. If you move them away from each other so they are now 4x the distance as they were originally, what happened to the electrical force between them?
Increased by 16x
Increased by 4x
Decreased to 1/2
Decreased to 1/4th
Decreased to 1/16th
None of these A B A B

26. Lesson 3 – Electric Field
Van de Graff & peanut
After hmwk:
VdG gen & pie tins

27. Electric Field What is always present around a charged object?
An electrical force
An electric field
Both of these
None of these

28. Electric Field
What happens to the strength of the electric field created by an object with a charge of –Q as you move away from it? -Q
Increases linearly
Increases more than linearly
Stays constant
Decreases linearly
Decreases more than linearly

29. Electric Field Lines
What is the correct diagram for the electric field lines illustrating the electric field around a negatively charged object? A. B. C. D.

30. Electric Field
Which is the correct direction of the electric field at the location x in space created by an object with a charge of +Q? A. B. C. D. E. +Q . x

31. Electric Field
A negatively charged peanut is repelled from an object with an unknown charged object. What is the direction of the electric field created by this unknown charged object.
Inward, towards the charged object
Outward, away from the charged object
Can’t be determined

32. Electric Field
What is the direction of the Electric field at the midpoint between the two identically charged objects? ↑ ↓  
No Electric field

33. Electric Field
Which sketch best shows the Electric field around two oppositely charged objects? A B D C

34. Capacitor
If there are two oppositely charged plates made of a conducting material, then a uniform Electric field is created between them. What is the charge on each plate?
Left: + Right: –
Left: – Right: +
Left: + Right: +
Left: – Right: –

35. Capacitor
If an electron is initially released from rest in the Electric field made by the capacitor, which way will it be forced? ↑ ↓  
It will stay at rest

36. Electric Field
If a proton is initially released from rest in the Electric field, which way will it be forced? ↑ ↓  
It will stay at rest

37. Electric Field
If a proton is initially released from rest in the uniform Electric field, how will it move?
at a constant velocity
at a constant acceleration
C. neither of these
D. can’t be determined

38. Lesson 4 – Electric Potential
Van de Graaff Generator in a line
Steel Wool & Cord

39. Disclaimer!
In this class we are going to simplify things and just worry about the interaction between electrons. Because of this electric potential energy will always be considered to be a positive value, and negatively charged objects will want to go from a high electric potential to a lower electric potential. This is different than what you will learn in college! But I believe this will give you a better conceptual understanding of electricity.

40. Electric Potential Energy
There are two electrons separated by a certain distance . In which arrangement is there more electric potential energy? A. B. C. Same D. can’t be determined

41. Electric Potential Energy vs Electric Potential
The two objects shown have the same electron density. The dots represent electrons. Which object has a more electric potential energy? 1 2
Both have the same
Can’t be determined 2 1

42. Electric Potential Energy vs Electric Potential
The two objects shown have the same electron density. (The dots represent electrons.)
Which object has a higher Electric Potential? 1 2
Both have the same
Can’t be determined 2 1

43. Electric Potential Energy vs Electric Potential
Which object has a higher Electric Potential? 3 4
Both have the same
Can’t be determined 4 3

44. Electric Potential Energy vs Electric Potential
Is it possible for Object 4 to have more electric potential energy (PE)?
Yes, it has to have more PE
Yes, it is possible
No, they have the same PE
No, it has to have less PE 4 3

45. Electric Potential Difference
Which pair of objects has a greater
Electric Potential Difference?
(Objects 1 & 2 have the same
electron “crowdedness”)
1 & 4
2 & 4
3 & 4
Can’t be determined 3 4 4 1 2 4

46. Electric Potential Difference
Which pair of objects has a greater
Electric Potential Difference?
(Objects 1, 2 & 3 have the same electron “crowdedness”)
1 & 4
2 & 4
3 & 4
All the same
Can’t be determined 4 1 2 4 4 3

47. Shocking 3 1 2 4 4 4 Which pair is most likely to get shocked?
(Objects 1 & 2 have the same
electron “crowdedness”)
1 & 4
2 & 4
3 & 4
Can’t be determined 3 4 4 1 2 4

48. Shocking Electrons continue to transfer until when?
Each object has the same number of electrons
Each object has the same electron density
When ALL the electrons have transferred
When the Electric Potential is equal to zero
None of these

49. Shocking
Which pair will experience a more painful shock? (Objects 1 and 2 have the same electron “crowdedness”.)
1 & 4
2 & 4
Both the same
Can’t be determined 2 4 4 1

50. Is in a car a safe place to be during a lightning storm?
Yes, b/c of the rubber tires
Yes, b/c of the metal frame
No, b/c of the rubber tires
No, b/c of the metal frame
No, it doesn’t matter, you’re just as at risk inside your car as you are outside

51. Lightning Rods What is the point of a lightning rod?
To give lightning an attractive place to strike and send the bolt along the cable along the outside of the building to the ground, rather than the building.
To prevent lightning from striking.
Both of these
Neither of these