1. Section 1 Electric Potential
Chapter 17
Objectives
Distinguish between electrical potential energy, electric potential, and potential difference.
Solve problems involving electrical energy and potential difference.
Describe the energy conversions that occur in a battery.

2. Electrical Potential Energy
Section 1 Electric Potential
Chapter 17
Electrical Potential Energy
Electrical potential energy -energy associated with a charge due to its position in an electric field.
Magnitude of charge in field plays a role!
ME = KE + PEgrav + PEelastic + PEelectric

3. Electrical Potential Energy, continued
Section 1 Electric Potential
Chapter 17
Electrical Potential Energy, continued
Electrical Potential Energy in a Uniform Electric Field
PEelectric = –qEd
PE =electrical potential energy
q=charge
E=electric field strength
d=distance
- PE increases in – charge and decreases if + charge

4. PE Charge and Direction
Toward E
Lose pe -
Gain pe +
Opposite E

5. Electrical Potential Energy
Section 1 Electric Potential
Chapter 17
Electrical Potential Energy

6. Section 1 Electric Potential
Chapter 17
Potential Difference
Electric Potential = work done against electric force to move a test charge a distance in an electric field.
V=volts= J/C

7. Potential difference is a change in electric potential.
Section 1 Electric Potential
Chapter 17
Potential difference is a change in electric potential.

8. Section 1 Electric Potential
Chapter 17
Potential Difference

9. Electric Potential
The potential difference in a uniform field varies with distance from a reference point.
Chapter 17
Test charge quantity is irrelevant!
Related to field strength only
Potential Difference in a Uniform Electric Field
∆V = –Ed
∆V= potential difference
E=magnitude of the electric field
d=displacement

10. Sample Problem Potential Energy and Potential Difference Chapter 17
Section 1 Electric Potential
Chapter 17
Sample Problem
Potential Energy and Potential Difference
A charge moves a distance of 2.0 cm in the direction of a uniform electric field whose magnitude is 215 N/C.As the charge moves, its electrical potential energy decreases by 6.9  J. Find the charge on the moving particle. What is the potential difference between the two locations?

11. Sample Problem, continued
Section 1 Electric Potential
Chapter 17
Sample Problem, continued
Potential Energy and Potential Difference
Given:
∆PEelectric = –6.9  10–19 J
d = m
E = 215 N/C
Unknown:
q = ?
∆V = ?

12. Sample Problem, continued
Section 1 Electric Potential
Chapter 17
Sample Problem, continued
Potential Energy and Potential Difference PEelectric = –qEd

13. Sample Problem, continued
Section 1 Electric Potential
Chapter 17
Sample Problem, continued
Potential Energy and Potential Difference

14. Potential Difference, continued
Section 1 Electric Potential
Chapter 17
Potential Difference, continued
At right, the electric potential at point A depends on the charge at point B and the distance r.
An electric potential exists at some point in an electric field regardless of whether there is a charge at that point.

15. Superposition Principle and Electric Potential
Section 1 Electric Potential
Chapter 17
Superposition Principle and Electric Potential

16. reference point for potential difference is infinity.
Section 1 Electric Potential
Chapter 17
reference point for potential difference is infinity.
Equation is

17. Section 2 Capacitance
Chapter 17
Objectives
Relate capacitance to the storage of electrical potential energy in the form of separated charges.
Calculate the capacitance of various devices.
Calculate the energy stored in a capacitor.

18. A capacitor stores electrical potential energy.
Section 2 Capacitance
Chapter 17 `
A capacitor stores electrical potential energy.
units for capacitance is the farad, F = (C/V)

19. Capacitors and Charge Storage, continued
Section 2 Capacitance
Chapter 17
Capacitors and Charge Storage, continued
Capacitance= charge/volts

20. Section 2 Capacitance
Chapter 17
Capacitance

21. Capacitance for a Parallel-Plate Capacitor in a Vacuum
Section 2 Capacitance
Chapter 17
Capacitance for a Parallel-Plate Capacitor in a Vacuum
Capacitance depends on size and material of a capacitor.
Ε=permitivity constant 8.85X10-12C2/N*m
D= distance
A=area

22. Capacitors and Charge Storage
Section 2 Capacitance
Chapter 17
Capacitors and Charge Storage
The material between a capacitor’s plates can change its capacitance.
Computer chips in essence act as 1 E6th tiny capacitors

23. Parallel-Plate Capacitor
Section 2 Capacitance
Chapter 17
Parallel-Plate Capacitor

24. Energy and Capacitors PE=1/2CV2
Section 2 Capacitance
Chapter 17
Energy and Capacitors
The potential energy stored in a charged capacitor depends on the charge and the potential difference between the capacitor’s two plates.
PE=1/2CV2

25. C= ε̧ A/d Honors Where ε = permitivity (from table) A=area
D=distance of plates

26. Summing up equations

27. Sample Problem Capacitance Given: Unknown: Chapter 17
Section 2 Capacitance
Chapter 17
Sample Problem
Capacitance
A capacitor, connected to a 12 V battery, holds 36 µC of charge on each plate. What is the capacitance of the capacitor? How much electrical potential energy is stored in the capacitor?
Given:
Q = 36 µC = 3.6  10–5 C
∆V = 12 V
Unknown:
C = ? PEelectric = ?

28. Sample Problem, continued
Section 2 Capacitance
Chapter 17
Sample Problem, continued
Capacitance
To determine the capacitance, use the definition of capacitance.

29. Sample Problem, continued
Section 2 Capacitance
Chapter 17
Sample Problem, continued
Capacitance
To determine the potential energy, use the alternative form of the equation for the potential energy of a charged capacitor:

30. Section 3 Current and Resistance
Chapter 17
Objectives
Describe the basic properties of electric current, and solve problems relating current, charge, and time.
Distinguish between the drift speed of a charge carrier and the average speed of the charge carrier between collisions.
Calculate resistance, current, and potential difference by using the definition of resistance.
Distinguish between ohmic and non-ohmic materials, and learn what factors affect resistance.

31. Current and Charge Movement
Section 3 Current and Resistance
Chapter 17
Current and Charge Movement
Electric current =rate at which electric charges pass through a circuit.
I=current measured in amperes or (amps) given area.

32. Section 3 Current and Resistance
Chapter 17
Conventional Current

33. Section 3 Current and Resistance
Chapter 17
Drift Velocity
Drift velocity is the the net velocity of a charge in an electric field.
Drift speeds are small

34. Ohm’s Law Resistance =opposition =to electric current .
Section 3 Current and Resistance
Chapter 17
Ohm’s Law
Resistance =opposition =to electric current .
units =ohm (Ω) volt / ampere.
R=Resistance
V=volts

35. Section 3 Current and Resistance
Chapter 17
Resistance to Current
Ohmic materials=resistance is constant over a range of voltage.
not true for all materials.
Resistance depends on
length,
cross-sectional area,
temperature, and material.

36. Factors that Affect Resistance
Section 3 Current and Resistance
Chapter 17
Factors that Affect Resistance

37. Section 3 Current and Resistance
Chapter 17
Resistance to Current
Resistors can be used to control the amount of current in a conductor.
Potentiometers (rheostats, variable resistors) have variable resistance.

38. Sources and Types of Current
Section 4 Electric Power
Chapter 17
Sources and Types of Current
Batteries and generators supply energy to charge carriers.
Current can be direct or alternating.
In direct current, charges move in a single direction.
In alternating current, the direction of charge movement continually alternates.

39. Section 4 Electric Power
Chapter 17
Energy Transfer
Electric power is the rate of conversion of electrical energy.
Electric companies measure energy consumed in kilowatt-hours. A kilowatt hour is equal to J.
Electrical energy is transferred at high voltage to minimize energy loss. Reduce current increase pressure.

40. Section 4 Electric Power
Chapter 17
Energy Transfer

41. Relating Kilowatt-Hours to Joules
Section 4 Electric Power
Chapter 17
Relating Kilowatt-Hours to Joules

43. Multiple Choice Chapter 17 Standardized Test Prep
1. What changes would take place if the electron moved from point A to point B in the uniform electric field?
A. The electron’s electrical potential energy would increase; its electric potential would increase.
B. The electron’s electrical potential energy would increase; its electric potential would decrease.
C. The electron’s electrical potential energy would decrease; its electric potential would decrease.
D. Neither the electron’s electrical potential energy nor its electric potential would change.

44. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
1. What changes would take place if the electron moved from point A to point B in the uniform electric field?
A. The electron’s electrical potential energy would increase; its electric potential would increase.
B. The electron’s electrical potential energy would increase; its electric potential would decrease.
C. The electron’s electrical potential energy would decrease; its electric potential would decrease.
D. Neither the electron’s electrical potential energy nor its electric potential would change.

45. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
2. What changes would take place if the electron moved from point A to point C in the uniform electric field?
F. The electron’s electrical potential energy would increase; its electric potential would increase.
G. The electron’s electrical potential energy would increase; its electric potential would decrease.
H. The electron’s electrical potential energy would decrease; its electric potential would decrease.
J. Neither the electron’s electrical potential energy nor its electric potential would change.

46. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
2. What changes would take place if the electron moved from point A to point C in the uniform electric field?
F. The electron’s electrical potential energy would increase; its electric potential would increase.
G. The electron’s electrical potential energy would increase; its electric potential would decrease.
H. The electron’s electrical potential energy would decrease; its electric potential would decrease.
J. Neither the electron’s electrical potential energy nor its electric potential would change.

47. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 3–4. A proton (q = 1.6  10–19 C) moves 2.0  10–6 m in the direction of an electric field that has a magnitude of 2.0 N/C. 3. What is the change in the electrical potential energy associated with the proton? A. –6.4  10–25 J B. –4.0  10–6 V C  10–25 J D  10–6 V

48. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 3–4. A proton (q = 1.6  10–19 C) moves 2.0  10–6 m in the direction of an electric field that has a magnitude of 2.0 N/C. 3. What is the change in the electrical potential energy associated with the proton? A. –6.4  10–25 J B. –4.0  10–6 V C  10–25 J D  10–6 V

49. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 3–4. A proton (q = 1.6  10–19 C) moves 2.0  10–6 m in the direction of an electric field that has a magnitude of 2.0 N/C. 4. What is the potential difference between the proton’s starting point and ending point? F. –6.4  10–25 J G. –4.0  10–6 V H  10–25 J J  10–6 V

50. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 3–4. A proton (q = 1.6  10–19 C) moves 2.0  10–6 m in the direction of an electric field that has a magnitude of 2.0 N/C. 4. What is the potential difference between the proton’s starting point and ending point? F. –6.4  10–25 J G. –4.0  10–6 V H  10–25 J J  10–6 V

51. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
5. If the negative terminal of a 12 V battery is grounded, what is the potential of the positive terminal? A. –12 V B. +0 V C. +6 V D. +12 V

52. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
5. If the negative terminal of a 12 V battery is grounded, what is the potential of the positive terminal? A. –12 V B. +0 V C. +6 V D. +12 V

53. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
6. If the area of the plates of a parallel-plate capacitor is doubled while the spacing between the plates is halved, how is the capacitance affected? F. C is doubled G. C is increased by four times H. C is decreased by 1/4 J. C does not change

54. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
6. If the area of the plates of a parallel-plate capacitor is doubled while the spacing between the plates is halved, how is the capacitance affected? F. C is doubled G. C is increased by four times H. C is decreased by 1/4 J. C does not change

55. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 7–8. A potential difference of 10.0 V exists across the plates of a capacitor when the charge on each plate is 40.0 µC. 7. What is the capacitance of the capacitor? A  10–4 F B  10–4 F C  10–6 F D  10–6 F

56. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 7–8. A potential difference of 10.0 V exists across the plates of a capacitor when the charge on each plate is 40.0 µC. 7. What is the capacitance of the capacitor? A  10–4 F B  10–4 F C  10–6 F D  10–6 F

57. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 7–8. A potential difference of 10.0 V exists across the plates of a capacitor when the charge on each plate is 40.0 µC. 8. How much electrical potential energy is stored in the capacitor? F  10–4 J G  10–4 J H  10–6 J J  10–6 J

58. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
Use the following passage to answer questions 7–8. A potential difference of 10.0 V exists across the plates of a capacitor when the charge on each plate is 40.0 µC. 8. How much electrical potential energy is stored in the capacitor? F  10–4 J G  10–4 J H  10–6 J J  10–6 J

59. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
9. How long does it take 5.0 C of charge to pass through a given cross section of a copper wire if I = 5.0 A? A s B. 1.0 s C. 5.0 s D. 25 s

60. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
9. How long does it take 5.0 C of charge to pass through a given cross section of a copper wire if I = 5.0 A? A s B. 1.0 s C. 5.0 s D. 25 s

61. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
10. A potential difference of 12 V produces a current of 0.40 A in a piece of copper wire. What is the resistance of the wire? F. 4.8 Ω G. 12 Ω H. 30 Ω J. 36 Ω

62. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
10. A potential difference of 12 V produces a current of 0.40 A in a piece of copper wire. What is the resistance of the wire? F. 4.8 Ω G. 12 Ω H. 30 Ω J. 36 Ω

63. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
11. How many joules of energy are dissipated by a 50.0 W light bulb in 2.00 s? A J B J C. 100 J D. 200 J

64. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
11. How many joules of energy are dissipated by a 50.0 W light bulb in 2.00 s? A J B J C. 100 J D. 200 J

65. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
12. How much power is needed to operate a radio that draws 7.0 A of current when a potential difference of 115 V is applied across it? F. 6.1  10–2 W G. 2.3  100 W H. 1.6  101 W J. 8.0  102 W

66. Multiple Choice, continued
Chapter 17
Standardized Test Prep
Multiple Choice, continued
12. How much power is needed to operate a radio that draws 7.0 A of current when a potential difference of 115 V is applied across it? F. 6.1  10–2 W G. 2.3  100 W H. 1.6  101 W J. 8.0  102 W

67. Chapter 17
Standardized Test Prep
Short Response
13. Electrons are moving from left to right in a wire. No other charged particles are moving in the wire. In what direction is the conventional current?

68. Short Response, continued
Chapter 17
Standardized Test Prep
Short Response, continued
13. Electrons are moving from left to right in a wire. No other charged particles are moving in the wire. In what direction is the conventional current? Answer: right to left

69. Short Response, continued
Chapter 17
Standardized Test Prep
Short Response, continued
14. What is drift velocity, and how does it compare with the speed at which an electric field travels through a wire?

70. Short Response, continued
Chapter 17
Standardized Test Prep
Short Response, continued
14. What is drift velocity, and how does it compare with the speed at which an electric field travels through a wire? Answer: Drift velocity is the net velocity of a charge carrier moving in an electric field. Drift velocities in a wire are typically much smaller than the speeds at which changes in the electric field propagate through the wire.

71. Short Response, continued
Chapter 17
Standardized Test Prep
Short Response, continued
15. List four factors that can affect the resistance of a wire.

72. Short Response, continued
Chapter 17
Standardized Test Prep
Short Response, continued
15. List four factors that can affect the resistance of a wire. Answer: length, cross-sectional area (thickness), temperature, and material

73. Chapter 17
Standardized Test Prep
Extended Response
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. a. Assuming that the capacitor is operating in a vacuum and that the permittivity of a vacuum (e0 = 8.85  10–12 C2/N•m2) can be used, determine the capacitance of the capacitor.

74. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. a. Assuming that the capacitor is operating in a vacuum and that the permittivity of a vacuum (e0 = 8.85  10–12 C2/N•m2) can be used, determine the capacitance of the capacitor. Answer: 3.10  10–13 F

75. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. b. How much charge will be stored on each plate of the capacitor when the capacitor’s plates are connected across a potential difference of 0.12 V?

76. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. b. How much charge will be stored on each plate of the capacitor when the capacitor’s plates are connected across a potential difference of 0.12 V? Answer: 3.7  10–14 C

77. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. c. What is the electrical potential energy stored in the capacitor when fully charged by the potential difference of 0.12 V?

78. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. c. What is the electrical potential energy stored in the capacitor when fully charged by the potential difference of 0.12 V? Answer: 2.2  10–15 J

79. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. d. What is the potential difference between a point midway between the plates and a point that is 1.10  10–4 m from one of the plates?

80. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. d. What is the potential difference between a point midway between the plates and a point that is 1.10  10–4 m from one of the plates? Answer: 3.4  10–2 V

81. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. e. If the potential difference of 0.12 V is removed from the circuit and the circuit is allowed to discharge until the charge on the plates has decreased to 70.7 percent of its fully charged value, what will the potential difference across the capacitor be?

82. Extended Response, continued
Chapter 17
Standardized Test Prep
Extended Response, continued
16. A parallel-plate capacitor is made of two circular plates, each of which has a diameter of 2.50  10–3 m. The plates of the capacitor are separated by a space of 1.40  10–4 m. e. If the potential difference of 0.12 V is removed from the circuit and the circuit is allowed to discharge until the charge on the plates has decreased to 70.7 percent of its fully charged value, what will the potential difference across the capacitor be? Answer: 8.5  10–2 V

83. Section 2 Capacitance
Chapter 17
Charging a Capacitor

84. A Capacitor With a Dielectric
Section 2 Capacitance
Chapter 17
A Capacitor With a Dielectric

85. Factors That Affect Resistance
Section 2 Capacitance
Chapter 17
Factors That Affect Resistance