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2. Standardized Test Prep
Resources
Chapter Presentation
Visual Concepts
Transparencies
Sample Problems
Standardized Test Prep

3. Chapter 17 Table of Contents Section 1 Electric Potential
Electrical Energy and Current
Table of Contents
Section 1 Electric Potential
Section 2 Capacitance
Section 3 Current and Resistance
Section 4 Electric Power

4. 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.

5. Electrical Potential Energy
Section 1 Electric Potential
Chapter 17
Electrical Potential Energy
Electrical potential energy is potential energy associated with a charge due to its position in an electric field.
Electrical potential energy is a component of mechanical energy.
ME = KE + PEgrav + PEelastic + PEelectric

6. Electrical Potential Energy, continued
Section 1 Electric Potential
Chapter 17
Electrical Potential Energy, continued
Electrical potential energy can be associated with a charge in a uniform field.
Electrical Potential Energy in a Uniform Electric Field
PEelectric = –qEd
electrical potential energy = –(charge)  (electric field strength)  (displacement from the reference point in the direction of the field)

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

8. Chapter 17 Potential Difference
Section 1 Electric Potential
Chapter 17
Potential Difference
Electric Potential equals the work that must be performed against electric forces to move a charge from a reference point to the point in question, divided by the charge.
The electric potential associated with a charge is the electric energy divided by the charge:

9. Potential Difference, continued
Section 1 Electric Potential
Chapter 17
Potential Difference, continued
Potential Difference equals the work that must be performed against electric forces to move a charge between the two points in question, divided by the charge.
Potential difference is a change in electric potential.

10. Section 1 Electric Potential
Chapter 17
Potential Difference

11. Potential Difference, continued
Section 1 Electric Potential
Chapter 17
Potential Difference, continued
The potential difference in a uniform field varies with the displacement from a reference point.
Potential Difference in a Uniform Electric Field
∆V = –Ed
potential difference = –(magnitude of the electric field  displacement)

12. Chapter 17 Sample Problem Potential Energy and Potential Difference
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?

13. 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 = ?

14. Sample Problem, continued
Section 1 Electric Potential
Chapter 17
Sample Problem, continued
Potential Energy and Potential Difference
Use the equation for the change in electrical potential energy.
PEelectric = –qEd
Rearrange to solve for q, and insert values.

15. Sample Problem, continued
Section 1 Electric Potential
Chapter 17
Sample Problem, continued
Potential Energy and Potential Difference
The potential difference is the magnitude of E times the displacement.

16. Potential Difference, continued
Section 1 Electric Potential
Chapter 17
Potential Difference, continued
At right, the electric poten-tial 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.

17. Potential Difference, continued
Section 1 Electric Potential
Chapter 17
Potential Difference, continued
The reference point for potential difference near a point charge is often at infinity.
Potential Difference Between a Point at Infinity and a Point Near a Point Charge
The superposition principle can be used to calculate the electric potential for a group of charges.

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

19. 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.

20. Capacitors and Charge Storage
Section 2 Capacitance
Chapter 17
Capacitors and Charge Storage
A capacitor is a device that is used to store electrical potential energy.
Capacitance is the ability of a conductor to store energy in the form of electrically separated charges.
The SI units for capacitance is the farad, F, which equals a coulomb per volt (C/V)

21. Capacitors and Charge Storage, continued
Section 2 Capacitance
Chapter 17
Capacitors and Charge Storage, continued
Capacitance is the ratio of charge to potential difference.

22. Section 2 Capacitance
Chapter 17
Capacitance

23. Capacitors and Charge Storage, continued
Section 2 Capacitance
Chapter 17
Capacitors and Charge Storage, continued
Capacitance depends on the size and shape of a capacitor.
Capacitance for a Parallel-Plate Capacitor in a Vacuum

24. Capacitors and Charge Storage, continued
Section 2 Capacitance
Chapter 17
Capacitors and Charge Storage, continued
The material between a capacitor’s plates can change its capacitance.
The effect of a dielectric is to reduce the strength of the electric field in a capacitor.

25. Capacitors in Keyboards
Section 2 Capacitance
Chapter 17
Capacitors in Keyboards

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

27. Chapter 17 Energy and Capacitors
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.

28. Chapter 17 Sample Problem Capacitance
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 = ?

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

30. 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:

31. 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.

32. Current and Charge Movement
Section 3 Current and Resistance
Chapter 17
Current and Charge Movement
Electric current is the rate at which electric charges pass through a given area.

33. Section 3 Current and Resistance
Chapter 17
Conventional Current

34. Chapter 17 Drift Velocity
Section 3 Current and Resistance
Chapter 17
Drift Velocity
Drift velocity is the the net velocity of a charge carrier moving in an electric field.
Drift speeds are relatively small because of the many collisions that occur when an electron moves through a conductor.

35. Section 3 Current and Resistance
Chapter 17
Drift Velocity

36. Chapter 17 Resistance to Current
Section 3 Current and Resistance
Chapter 17
Resistance to Current
Resistance is the opposition presented to electric current by a material or device.
The SI units for resistance is the ohm (Ω) and is equal to one volt per ampere.
Resistance

37. Resistance to Current, continued
Section 3 Current and Resistance
Chapter 17
Resistance to Current, continued
For many materials resistance is constant over a range of potential differences. These materials obey Ohm’s Law and are called ohmic materials.
Ohm’s low does not hold for all materials. Such materials are called non-ohmic.
Resistance depends on length, cross-sectional area, temperature, and material.

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

39. Resistance to Current, continued
Section 3 Current and Resistance
Chapter 17
Resistance to Current, continued
Resistors can be used to control the amount of current in a conductor.
Salt water and perspiration lower the body's resistance.
Potentiometers have variable resistance.

40. Section 4 Electric Power
Chapter 17
Objectives
Differentiate between direct current and alternating current.
Relate electric power to the rate at which electrical energy is converted to other forms of energy.
Calculate electric power and the cost of running electrical appliances.

41. 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.

42. Electric power = current  potential difference
Section 4 Electric Power
Chapter 17
Energy Transfer
Electric power is the rate of conversion of electrical energy.
Electric power
P = I∆V
Electric power = current  potential difference

43. Section 4 Electric Power
Chapter 17
Energy Transfer

44. Energy Transfer, continued
Section 4 Electric Power
Chapter 17
Energy Transfer, continued
Power dissipated by a resistor
Electric companies measure energy consumed in kilowatt-hours.
Electrical energy is transferred at high potential differences to minimize energy loss.

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

46. Chapter 17 Multiple Choice 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.

47. 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.

48. 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.

49. 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.

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.
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

51. 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

52. 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

53. 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

54. 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

55. 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

56. 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

57. 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

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.
7. What is the capacitance of the capacitor?
A  10–4 F
B  10–4 F
C  10–6 F
D  10–6 F

59. 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

60. 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

61. 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

62. 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

63. 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

64. 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

65. 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

66. 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

67. 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

68. 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

69. 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

70. Chapter 17 Short Response
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?

71. 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

72. 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?

73. 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.

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

75. 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

76. Chapter 17 Extended Response
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.

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.
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

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.
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?

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.
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

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.
c. What is the electrical potential energy stored in the capacitor when fully charged by the potential difference of 0.12 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.
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

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.
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?

83. 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

84. 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?

85. 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

86. Section 2 Capacitance
Chapter 17
Charging a Capacitor

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

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