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2. Standardized Test Prep
Resources
Chapter Presentation
Bellringers
Transparencies
Standardized Test Prep
Math Skills
Visual Concepts

3. Chapter 16 Table of Contents Section 1 Electrical Charge and Force
Electricity
Table of Contents
Section 1 Electrical Charge and Force
Section 2 Current
Section 3 Circuits

4. Section 1 Electrical Charge and Force
Chapter 16
Objectives
Indicate which pairs of charges will repel and which will attract.
Explain what factors affect the strength of the electric force.
Describe the characteristics of the electric field due to a charge.

5. Section 1 Electrical Charge and Force
Chapter 16
Bellringer
Static electricity is a part of life. Can you name at least five examples of static electricity that occur in your home?
Fabric softeners are commonly used today because they eliminate static cling.
Explain why clothes in the dryer get static cling.
Why can walking across a carpeted room be a shocking experience?

6. Chapter 16 Electric Charge
Section 1 Electrical Charge and Force
Chapter 16
Electric Charge
Electric charge is an electrical property of matter that creates electric and magnetic forces and interactions.
Like charges repel, and opposite charges attract.
The two types of charges are called positive and negative.
An object’s electric charge depends on the imbalance of its protons and electrons.
Electrons are negatively charged, protons are positively charged, and neutrons are neutral (no charge).

7. Section 1 Electrical Charge and Force
Chapter 16
Electric Charge

8. Electric Charge, continued
Section 1 Electrical Charge and Force
Chapter 16
Electric Charge, continued
Negatively charged objects have more electrons than protons.
Positively charged objects have fewer electrons than protons.
The SI unit of electric charge is the coulomb, C.
A proton has a charge of 1.6  10–19 C
An electron has a charge of 1.6  10–19 C.
The net electric charge of a charged object is always a multiple of 1.6  10–19 C.

9. Characteristics of Electric Charge
Section 1 Electrical Charge and Force
Chapter 16
Characteristics of Electric Charge

10. Electric Charge, continued
Section 1 Electrical Charge and Force
Chapter 16
Electric Charge, continued
Conductors allow charges to flow; insulators do not.
An electrical conductor is a material in which charges can move freely and that can carry an electric current.
An electrical insulator is a material that does not transfer current easily.
Objects can be charged by the transfer of electrons.
The outermost electrons can be easily transferred from one atom to another.
Charging by friction is when one material gains electrons and becomes negatively charged, and the other loses electrons and becomes positively charged.

11. Electrical Conductors and Insulators
Section 1 Electrical Charge and Force
Chapter 16
Electrical Conductors and Insulators

12. Section 1 Electrical Charge and Force
Chapter 16
Friction

13. Electric Charge, continued
Section 1 Electrical Charge and Force
Chapter 16
Electric Charge, continued
Objects can also be charged without friction.
One way to charge a neutral object without friction is by touching it with a charged object.
Objects charged in this manner are said to be charged by contact.
Charges move within uncharged objects.
The charges in a neutral conductor can be redistributed without contacting a charged object.
Although the total charge on the conductor will be zero, the opposite sides will have an induced charge.
This polarization of the atoms or molecules of an insulator produces an induced charge on the surface of the insulator.

14. Chapter 16 Charging by Contact Section 1 Electrical Charge and Force
When a negative rod touches a neutral doorknob, electrons move from the rod to the doorknob.
The transfer of electrons to the metal doorknob gives the doorknob a net negative charge.

15. Section 1 Electrical Charge and Force
Chapter 16
Charging by Contact

16. Section 1 Electrical Charge and Force
Chapter 16
Induced Charges

17. Chapter 16 Electric Force
Section 1 Electrical Charge and Force
Chapter 16
Electric Force
Electric force is the force of attraction or repulsion between objects due to charge.
The electric force at the atomic and molecular level is responsible for most of the common forces we can observe.
The electric force is also responsible for effects that we can’t see.
Electric force depends on charge and distance.
The electric force between two objects is proportional to the product of the charges on the objects.
The electric force is inversely proportional to the square of the distance between two objects.

18. Electric Force, continued
Section 1 Electrical Charge and Force
Chapter 16
Electric Force, continued
Electric force acts through a field.
An electric field is a region in space around a charged object that causes a stationary charged object to experience an electric force.
One way to show an electric field is by drawing electric field lines.
Electric field lines point in the direction of the electric force on a positive charge.
The electric field lines around a positive charge point outward.
The electric field lines around a negative charge point inward.

19. Section 1 Electrical Charge and Force
Chapter 16
Electric Field Lines

20. Section 1 Electrical Charge and Force
Chapter 16
Electric Field Lines

21. Electric Force, continued
Section 1 Electrical Charge and Force
Chapter 16
Electric Force, continued
Electric field lines never cross one another.
Field lines show both the direction of an electric field and the relative strength due to a given charge.
More lines are drawn for greater charges to indicate greater force.

22. Electric Fields and Test Charges
Section 1 Electrical Charge and Force
Chapter 16
Electric Fields and Test Charges

23. Chapter 16 Objectives Describe how batteries are sources of voltage.
Section 2 Current
Objectives
Describe how batteries are sources of voltage.
Explain how a potential difference produces a current in a conductor.
Define resistance.
Calculate the resistance, current, or voltage, given the other two quantities.
Distinguish between conductors, superconductors, semiconductors, and insulators.

24. Chapter 16
Section 2 Current
Bellringer
Dry cell batteries are a source of mobile electrical power. Name five devices that use dry cell batteries.
Give reasons why copper is normally used to wire a home for electricity.
Why is it important to unplug a device by pulling the plug instead of by yanking it out of the socket by pulling on the electrical cord?
Why are electrical appliances, such as razors, hair dryers, and curling irons, not to be used in the bathtub or shower?

25. Chapter 16 Voltage and Current
Section 2 Current
Voltage and Current
Electrical potential energy is the ability to move an electric charge from one point to another.
The electrical potential energy of the moving charge decreases because the electric field does work on the charge.
The electrical potential energy depends on the distance between two charged objects for both an attractive and a repulsive electric force.

26. Electrical Potential Energy
Chapter 16
Section 2 Current
Electrical Potential Energy
The electrical potential energy between two negative charges decreases as the distance between them increases.

27. Electrical Potential Energy and Relative Position
Chapter 16
Section 2 Current
Electrical Potential Energy and Relative Position
The electrical potential energy of a charge depends on its position in an electric field.

28. Electrical Potential Energy
Chapter 16
Section 2 Current
Electrical Potential Energy

29. Voltage and Current, continued
Chapter 16
Section 2 Current
Voltage and Current, continued
Potential difference is measured in volts.
The potential difference between any two points, is the work that must be done against electric forces to move a unit charge from one point to the other.
The volt, V, is equivalent to one joule per coulomb (1 J/C).
Potential difference is often called voltage.

30. Chapter 16
Section 2 Current
Potential Difference

31. Chapter 16
Section 2 Current
Voltage

32. Voltage and Current, continued
Chapter 16
Section 2 Current
Voltage and Current, continued
There is a voltage across the terminals of a battery.
A cell is a device that is a source of electric current because of a potential difference, or voltage, between the terminals.
One terminal is positive, and the other is negative.
Batteries convert chemical energy into electrical energy.

33. Chapter 16
Section 2 Current
Battery

34. Chapter 16
Section 2 Current
Electric Cell

35. Voltage and Current, continued
Chapter 16
Section 2 Current
Voltage and Current, continued
A voltage sets charges in motion.
Current is the rate that electric charges move through a conductor.
The SI unit of current is the ampere, A.
1 amp = 1 C/s
A battery is a direct current source because the charges always move from one terminal to the other in the same direction.
Conventional current is defined as movement of positive charge.
The direction of current in a wire is opposite the direction that electrons move in that wire.

36. Comparing Direct and Alternating Current
Chapter 16
Section 2 Current
Comparing Direct and Alternating Current

37. Chapter 16
Section 2 Current
Conventional Current

38. Electrical Resistance
Chapter 16
Section 2 Current
Electrical Resistance
Resistance is the opposition posed by a material or a device to the flow of current.
Resistance is caused by internal friction, which slows the movement of charges through a conducting material.
Resistance can be calculated from current and voltage.
The SI unit of resistance is the ohm, Ω. 1 Ω = 1 V/A
A resistor is a special type of conductor used to control current.

39. Chapter 16
Section 2 Current
Math Skills
Resistance The headlights of a typical car are powered by a 12 V battery. What is the resistance of the headlights if they draw 3.0 A of current when turned on?
1. List the given and unknown values.
Given: current, I = 3.0 A
voltage, V = 12 V
Unknown: resistance, R = ? Ω

40. Chapter 16 Math Skills, continued
Section 2 Current
Math Skills, continued
2. Write the equation for resistance.
3. Insert the known values into the equation, and solve.
R = 4.0 

41. Electrical Resistance, continued
Chapter 16
Section 2 Current
Electrical Resistance, continued
Conductors have low resistances.
Some materials become superconductors below a certain temperature.
Certain metals and compounds have zero resistance when their temperature falls below a certain temperature called the critical temperature.
Semiconductors are intermediate to conductors and insulators.
The controlled addition of specific atoms of other materials as impurities dramatically increases a semiconductor’s ability to conduct electric charge.

42. Chapter 16 Objectives Use schematic diagrams to represent circuits.
Section 3 Circuits
Objectives
Use schematic diagrams to represent circuits.
Distinguish between series and parallel circuits.
Calculate electric power using voltage and current.
Explain how fuses and circuit breakers are used to prevent circuit overload.

43. Chapter 16 Bellringer Section 3 Circuits
1. Inexpensive electrical power is essential. List at least ten electrical devices that you have used today.
2. In some strings of Christmas lights, none of the lights work if one light is burned out. What is a possible explanation for this?
3. A big feast is being prepared for several people in a home. The cooks are using a turkey roaster, the oven, an electric mixer, the blender, and the toaster. Every light is on and so is the refrigerator. All at once the power in the kitchen goes out. What is an explanation for this, and how can it be corrected?

44. Chapter 16 What Are Circuits?
Section 3 Circuits
What Are Circuits?
An electric circuit is a path through which charges can be conducted.
An electric circuit is a set of electrical components connected such that they provide one or more complete paths for the movement of charges.
The conducting path produced when a light bulb is connected across the battery’s terminals is called a closed circuit.
Without a complete path, there is no charge flow and therefore no current. This is called an open circuit.

45. Chapter 16
Section 3 Circuits
Electric Circuit

46. What Are Circuits?, continued
Chapter 16
Section 3 Circuits
What Are Circuits?, continued
Switches interrupt the flow of charges in a circuit.
You can use a switch to open and close a circuit.
Schematic diagrams are used to represent circuits.
A schematic diagram is a graphical representation of a circuit that uses lines to represent wires and different symbols to represent components.
Each element used in a piece of electrical equipment is represented by a symbol that reflects the element’s construction or function.

47. Schematic Diagram and Common Symbols
Chapter 16
Section 3 Circuits
Schematic Diagram and Common Symbols

48. Series and Parallel Circuits
Chapter 16
Section 3 Circuits
Series and Parallel Circuits
Series circuits have a single path for current.
When appliances or other devices are connected in a series circuit, they form a single pathway for charges to flow.
In a series circuit, the components of a circuit form a single path for current.
The current in each device is the same.
The resistances may be different.
The voltage across each device in a series circuit can be different.
If one element along the path in a series circuit is removed, the circuit will not work.

49. Chapter 16
Section 3 Circuits
Resistors in Series

50. Series and Parallel Circuits, continued
Chapter 16
Section 3 Circuits
Series and Parallel Circuits, continued
Parallel circuits have multiple paths for current.
A parallel circuit is a circuit in which all of the components are connected to each other side by side.
The voltage across each device is the same.
The current in each device does not have to be the same.
A break in any one path in a parallel circuit does not interrupt the flow of electric charge in the other paths.

51. Chapter 16
Section 3 Circuits
Resistors in Parallel

52. Chapter 16 Series and Parallel Section 3 Circuits
When bulbs are connected in series, charges must pass through both light bulbs to complete the circuit.
When devices are connected in parallel, charges have more than one path to follow. The circuit can be complete even if one light bulb burns out.

53. Electric Power and Electrical Energy
Chapter 16
Section 3 Circuits
Electric Power and Electrical Energy
Electrical energy is the energy that is associated with charged particles because of their positions.
Electric power is the rate at which electrical energy is used in a circuit.
The rate at which electrical work is done is called electric power.
The SI unit for power is the watt (W).
1 W = 1 A  1 V

54. Electric Power and Electrical Energy, continued
Chapter 16
Section 3 Circuits
Electric Power and Electrical Energy, continued
If you combine the electric power equation above with the equation V = IR, the power lost, or dissipated, by a resistor can be calculated.
Electric companies measure energy consumed in kilowatt-hours.
1 kW•h = 3.6  106 J.

55. Equation for Electric Power
Chapter 16
Section 3 Circuits
Equation for Electric Power

56. Chapter 16
Section 3 Circuits
Math Skills
Electric Power When a hair dryer is plugged into a 120 V outlet, it has a 9.1 A current in it. What is the hair dryer’s power rating?
1. List the given and unknown values.
Given: voltage, V = 120 V
current, I = 9.1 A
Unknown: electric power, P = ? W

57. Chapter 16 Math Skills, continued
Section 3 Circuits
Math Skills, continued
2. Write the equation for electric power.
power = current × voltage
P = IV
3. Insert the known values into the equation, and solve.
P = (9.1 A)(120 V)
P = 1.1 × 103 W

58. Fuses and Circuit Breakers
Chapter 16
Section 3 Circuits
Fuses and Circuit Breakers
When electrical wires carry more than a safe level of current, the circuit is said to be overloaded.
A short circuit can happen if a wire’s insulation wears down, two wires may touch, creating an alternative pathway for current.
Fuses melt to prevent circuit overloads.
A fuse an electrical device that contains a metal strip that melts when current in the circuit becomes too great.

59. Fuses and Circuit Breakers
Chapter 16
Section 3 Circuits
Fuses and Circuit Breakers
Circuit breakers open circuits with high current.
A circuit breaker a switch that opens a circuit automatically when the current exceeds a certain value.
The circuit breaker acts as a switch.
Unlike fuses, circuit breakers can be reset by turning the switch back on.

60. Chapter 16
Section 3 Circuits
Fuse

61. Chapter 16
Section 3 Circuits
Concept Mapping

62. Understanding Concepts
Chapter 16
Standardized Test Prep
Understanding Concepts
1. A 12-volt battery is connected to a light bulb that has a resistance of 240 ohms. Calculate the amount of current in amperes drawn by the circuit.
A A
B. 0.5 A
C. 2.0 A
D A

63. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
1. A 12-volt battery is connected to a light bulb that has a resistance of 240 ohms. Calculate the amount of current in amperes drawn by the circuit.
A A
B. 0.5 A
C. 2.0 A
D A

64. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
2. Which of the following statements is true?
F. Electrical forces exist between any two neutral particles.
G. Electrical forces exist between any two charged particles.
H. Electrical forces exist only between particles with the same charge.
I. Electrical forces exist only between particles with opposite charges.

65. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
2. Which of the following statements is true?
F. Electrical forces exist between any two neutral particles.
G. Electrical forces exist between any two charged particles.
H. Electrical forces exist only between particles with the same charge.
I. Electrical forces exist only between particles with opposite charges.

66. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
3. What happens to an object that is charged by induction?
A. It acquires excess electrons.
B. It remains electrically neutral.
C. It acquires a net charge from the object that is inducing the charge.
D. A current exists between it and the object that is inducing the charge.

67. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
3. What happens to an object that is charged by induction?
A. It acquires excess electrons.
B. It remains electrically neutral.
C. It acquires a net charge from the object that is inducing the charge.
D. A current exists between it and the object that is inducing the charge.

68. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
4. A stream of water is deflected when a negatively charged rod is held close to it. Use the concept of induced charge to explain what happens.

69. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
4. A stream of water is deflected when a negatively charged rod is held close to it. Use the concept of induced charge to explain what happens.
Answer: A charge is induced on the water by the charged rod. Attraction between the charged part of the stream and the rod deflects the flow.

70. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
5. How does a fuse protect a circuit from overloading?

71. Understanding Concepts, continued
Chapter 16
Standardized Test Prep
Understanding Concepts, continued
5. How does a fuse protect a circuit from overloading?
Answer: The fuse has a thin wire with a low melting point. When electrical resistance increases the temperature too high, it melts and breaks the circuit.

72. Chapter 16 Reading Skills
Standardized Test Prep
Reading Skills
In 1909 Robert Millikan measured the charge on an electron in what is known as the oil-drop experiment. He sprayed oil droplets into a chamber. Two plates with opposite charges produced an electric field. Some of the drops acquired a negative charge. The field was adjusted so there was an upward force equal to the downward pull of gravity. From the strength of this force, Millikan could calculate the amount of the electric charge on the drop.
6. Analyze how the electric field could cause an oil drop to float inside the chamber.

73. Reading Skills, continued
Chapter 16
Standardized Test Prep
Reading Skills, continued
6. Analyze how the electric field could cause an oil drop to float inside the chamber.
Answer: Electrical forces between the charged particle an the charged plates balance the downward pull of gravity.

74. Interpreting Graphics
Chapter 16
Standardized Test Prep
Interpreting Graphics
7. Which metal would be the best choice for a power line, based on electrical resistance?
F. aluminum
G. iron
H. lead
I. silver

75. Interpreting Graphics
Chapter 16
Standardized Test Prep
Interpreting Graphics
7. Which metal would be the best choice for a power line, based on electrical resistance?
F. aluminum
G. iron
H. lead
I. silver

76. Interpreting Graphics
Chapter 16
Standardized Test Prep
Interpreting Graphics
8. Which metal would most likely be then best substitute for the tungsten filament in an incandescent light bulb based on resistance?
A. aluminum
B. iron
C. lead
D. silver

77. Interpreting Graphics
Chapter 16
Standardized Test Prep
Interpreting Graphics
8. Which metal would most likely be then best substitute for the tungsten filament in an incandescent light bulb based on resistance?
A. aluminum
B. iron
C. lead
D. silver