1. Electrostatics

2. http://www.nearingzero.net (nz192.jpg)

3. A Bit of History Ancient Greeks
Observed electric and magnetic phenomena as early as 700 BC
Found that amber, when rubbed, became electrified and attracted pieces of straw or feathers
Magnetic forces were discovered by observing magnetite attracting iron

4. A Bit More History William Gilbert Charles Coulomb 1600
Found that electrification was not limited to amber
Charles Coulomb
1785
Confirmed the inverse square relationship of electrical forces

5. History Final Hans Oersted Michael Faraday 1820
Compass needle deflects when placed near an electrical current
Michael Faraday
A wire moved near a magnet, an electric current is observed in the wire

6. Properties of Electric Charges
Two types of charges exist
They are called positive and negative
Named by Benjamin Franklin
Like charges repel and unlike charges attract one another

7. Question #2
The charge on sphere 2 is three times the charge on sphere 1. Which force diagram is correct? (e) is none of the others.

8. Answer #2: (d)
The charge on sphere 2 is three times the charge on sphere 1. Which force diagram is correct? (e) is none of the others.

9. More Properties of Charge
Nature’s basic carrier of positive charge is the proton
Protons do not move from one material to another because they are held firmly in the nucleus
Nature’s basic carrier of negative charge is the electron
Gaining or losing electrons is how an object becomes charged
Electrons are found in the electron cloud outside of the nucleus
Neutrons are electrically neutral and have no charge and are found inside the nucleus

10. Bohr Model of the Atom

11. More Properties of Charge
Electric charge is always conserved
Charge is not created, only exchanged
Objects become charged because negative charge is transferred from one object to another

12. Properties of Charge, final
Charge is quantized
All charge is a multiple of a fundamental unit of charge, symbolized by e
Electrons have a charge of –e
Protons have a charge of +e
The SI unit of charge is the Coulomb (C)
e = x C

13. Conductors
Conductors are materials in which the electric charges move freely
Copper, aluminum and silver are good conductors
When a conductor is charged in a small region, the charge readily distributes itself over the entire surface of the material

14. Insulators
Insulators are materials in which electric charges do not move freely
Glass and rubber are examples of insulators
When insulators are charged by rubbing, only the rubbed area becomes charged
There is no tendency for the charge to move into other regions of the material

15. Semiconductors
The characteristics of semiconductors are between those of insulators and conductors
Silicon and germanium are examples of semiconductors

16. Charging…
Two ways
Electrification by Contact (EBC)
Induction

17. Charging by Friction
Self-explanatory…
(demo)

18. Charging by EBC
A charged object (the rod) is physically touches the other uncharged, object (the sphere)
The same type of charge is CONDUCTED from the rod to the sphere

19. Charging by Induction

20. Charging by Induction

21. Charging by Induction
NO physical contact between between charged & uncharged object
OPPOSITE charged is INDUCED

22. Question #3
An alpha particle with two positive charges and a less-massive electron with a single negative charge are attracted to each other.
The force on the electron is:
Greater than that on the alpha particle
Less than that on the alpha particle
Same as that on the alpha particle
I haven’t a clue…

23. Answer #3: (c) Same
The force on the electron the same as that on the alpha particle - Newton’s Third Law.

24. Question #4
An alpha particle with two positive charges and a less-massive electron with a single negative charge are attracted to each other.
The particle with the most acceleration is the
Alpha particle
Electron
Neither - they have the same acceleration
I haven’t a clue…

25. Answer #4: (b) Electron
The particle with the most acceleration is the ELECTRON. Newton’s Second Law (F=ma)

26. Question #5
An alpha particle with two positive charges and a less-massive electron with a single negative charge are attracted to each other. As the particles get closer to each other, each experiences an increase in:
force
speed
acceleration
All of these
None of these

27. Answer #5: (d) ALL
As the particles get closer, the FORCE  and thus the ACCELERATION  and also the SPEED 

28. Coulomb’s Law Governs forces and charges,
ke is called the Coulomb Constant
ke = 8.99 x 109 N m2/C2
Typical charges can be in the µC range
Remember that force is a vector quantity

29. Question #6
If q1 = +20 C and q2 = +10 C and the two charges are 3 meters apart, what is the MAGNITUDE of the force between them?
0.2 N
0.6 N
22.22 N
2.0 x N
I don’t have a clue

30. Answer #6: (a) 0.2 N

31. Vector Nature of Electric Forces
Two point charges are separated by a distance r
The like charges produce a repulsive force between them
The force on q1 is equal in magnitude and opposite in direction to the force on q2

32. Vector Nature of Forces, cont.
Two point charges are separated by a distance r
The unlike charges produce a attractive force between them
The force on q1 is equal in magnitude and opposite in direction to the force on q2

33. Question #7
If q1 = +20 C and q2 = +10 C and the two charges are 3 meters apart, what is the DIRECTION of the force between them?
Away from each other
Towards each other
One chases the other
Nothing - they don’t move at all
I don’t have a clue

34. Answer #7: (a) Away Like charges repel
If q1 = +20 C and q2 = +10 C and the two charges are 3 meters apart, what is the DIRECTION of the force between them?
Like charges repel

35. Electrical Field
An electric field is said to exist in the region of space around a charged object
When another charged object enters this electric field, the field exerts a force on the second charged object

36. Electric Field, cont.
A charged particle, with charge Q, produces an electric field in the region of space around it
A small test charge, qo, placed in the field, will experience a force

37. Electric Field
Mathematically,
The electric field is a vector quantity

38. Question #9
What is the magnitude of the electric field 0.50 meters away from a -3C point charge?
1.08 x 105 N/C
-1.08 x 105 N/C
5.4 x 104 N/C
-5.4 x 104 N/C
I don’t have a clue…

39. Answer #9: (a) 1.08x105 N/C
What is the magnitude of the electric field 0.50 meters away from a -3C point charge?
1.08 x 105 N/C
-1.08 x 105 N/C
5.4 x 104 N/C
-5.4 x 104 N/C
I don’t have a clue…

40. Question #9
What is the magnitude of the electric field 0.50 meters away from a -3C point charge?
1.08 x 105 N/C
-1.08 x 105 N/C
5.4 x 104 N/C
-5.4 x 104 N/C
I don’t have a clue…

41. Direction of Electric Field
The electric field produced by a negative charge is directed toward the charge
A positive test charge would be attracted to the negative source charge

42. Direction of Electric Field, cont
The electric field produced by a positive charge is directed away from the charge
A positive test charge would be repelled from the positive source charge

43. Question #10
What is the electrostatic force acting on a 2 nC charge placed in a 335 N/C electric field?
0 N
6.7 x 10-4 N
6.7 x 10-7 N
6.7 N
I don’t have a clue…

44. Answer #10: (c) 6.7 x 10-7 N
What is the electrostatic force acting on a 2 nC charge placed in a 335 N/C electric field?

45. Electric Field Lines
A convenient aid for visualizing electric field patterns is to draw lines pointing in the direction of the field vector at any point
These are called electric field lines and were introduced by Michael Faraday

46. Electric Field Lines, cont.
The field lines are related to the field by
The electric field vector, E, is tangent to the electric field lines at each point
The number of lines per unit area through a surface perpendicular to the lines is proportional to the strength of the electric field in a given region

47. Electric Field Line Patterns
Point charge
The lines radiate equally in all directions
For a positive source charge, the lines will radiate outward

48. Electric Field Line Patterns
For a negative source charge, the lines will point inward

49. Electric Field Line Patterns
An electric dipole consists of two equal and opposite charges
The high density of lines between the charges indicates the strong electric field in this region

50. Electric Field Line Patterns
Two equal but like point charges
At a great distance from the charges, the field would be approximately that of a single charge of 2q
The bulging out of the field lines between the charges indicates the repulsion between the charges
The low field lines between the charges indicates a weak field in this region

51. Electric Field Patterns
Unequal and unlike charges
Note that two lines leave the +2q charge for each line that terminates on -q

52. Electric Field Lines

53. Electric Field Lines

54. Electric Field Lines

55. Electrostatics
The End…