1. Chapter 7 Section 1 Electric Charge
Electricity
Chapter 7 Section 1
Electric Charge

2. Sections 1. Electric Charge slides 3 - 35
2. Electric Current slides
3. Electrical Energy slides

3. Electric Charge
The center of an atom is made of protons (+) and neutrons (no charge).

4. Electric Charge
The center of an atom is made of protons (+) and neutrons (no charge).
Electrons (-) move around the center of the atom.

5. Electric Charge The amount of + Charge on a proton = The amount of –
Charge on an electron.

6. Electric Charge The amount of + Charge on a proton = The amount of –
Charge on an electron.
Each atom has the same number of protons & electrons making them electrically neutral.

7. Electricity
Atoms have no charge.

8. Electricity
Atoms have no charge.
- ion if it gains electrons

9. Electricity Atoms have no charge. - ion if it gains electrons
+ ion if it loses electrons

10. Electricity Atoms have no charge. - ion if it gains electrons
+ ion if it loses electrons
Electrons can move from atom to atom or from object to object.

11. Static Electricity
Is the buildup of charges on an object.

12. Static Electricity Is the buildup of charges on an object.
When there is static electricity, the electric charges are not balanced.

13. Static Electricity Is the buildup of charges on an object.
When there is static electricity, the electric charges are not balanced.
The Law of Conservation of charge states that charge can be transferred from object to object but it cannot be created or destroyed.

14. Electricity
Opposite charges attract
Like charges repel + - + + - -

15. Electricity
The electric force between charged objects depends on how far apart they are.

16. Electricity
The electric force between charged objects depends on how far apart they are.
The force decreases the farther apart the charges are.

17. Electricity
The electric force between charged objects depends on how far apart they are.
The force decreases the farther apart the charges are.
The electric force also depends upon the amount of charge on the objects.

18. Electricity
The electric force between charged objects depends on how far apart they are.
The force decreases the farther apart the charges are.
The electric force also depends upon the amount of charge on the objects.
More charge = More force

19. Electric Field Area around every electric charge that exerts a force.
Movement of a positive charge in electric fields. + -

20. Electric & Gravitational Force
Electric forces are stronger than gravity.

21. Electric & Gravitational Force
Electric forces are stronger than gravity.
Atoms are held together by electric forces.

22. Electric & Gravitational Force
Electric forces are stronger than gravity.
Atoms are held together by electric forces.
These forces cause chemical bonds to make a new substance.

23. Electric & Gravitational Force
Electric forces are stronger than gravity.
Atoms are held together by electric forces.
These forces cause chemical bonds to make a new substance.
Electric forces between atoms are greater than the gravitational forces between atoms.

24. Electric & Gravitational Force
Electric forces are stronger than gravity.
Atoms are held together by electric forces.
These forces cause chemical bonds to make a new substance.
Electric forces between atoms are greater than the gravitational forces between atoms.
Electric forces between most objects are less than the gravitational forces between them because most objects are elec. neutral.

25. Conductors & Insulators
Electrons move more easily in conductors.

26. Conductors & Insulators
Electrons move more easily in conductors. Ex. Metals such as copper
Insulators do not allow electrons to move as easily. Ex. Plastic, wood rubber and glass

27. Charging Objects
Charging by contact- transferring charges by touching or rubbing ex. Clothes in a dryer

28. Charging Objects
Charging by contact- transferring charges by touching or rubbing ex. Clothes in a dryer
Charging by induction- charged object rearranges the electrons on a nearby neutral object.

29. Lightning
Large static discharge between clouds and the ground that causes atoms & molecules to light up.

30. Lightning
Large static discharge between clouds and the ground that causes atoms & molecules to light up.
Thunder- Electric energy in a lightning bolt rips electrons off atoms in the air causing great amounts of heat, up to 25,000 °C.

31. Lightning
Large static discharge between clouds and the ground that causes atoms & molecules to light up.
Thunder- Electric energy in a lightning bolt rips electrons off atoms in the air causing great amounts of heat, up to 25,000 °C.
The heat makes the air around the lightning bolt move faster creating sound waves.

32. Grounding
Grounding avoids damage by providing a path for electric charge to move to earth.

33. Electroscope Can detect when an object has an electric charge.
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34. Electroscope Can detect when an object has an electric charge.
The metal rod is a conductor.

35. Electroscope Can detect when an object has an electric charge.
The metal rod is a conductor.
When the leaves have a charge they repel each other and spread apart.

36. Electric Current
Chp 7 Section 2

37. Electric Current
The net movement of electric charges in one direction.

38. Electric Current
The net movement of electric charges in one direction.
Measured in units called amperes or amps.

39. Electric Current
The net movement of electric charges in one direction.
Measured in units called amperes or amps.
Symbol for amperes is A.

40. Electric Current
The net movement of electric charges in one direction.
Measured in units called amperes or amps.
Symbol for amperes is A.
Measures the electrons that flow past one point.

41. Electric Current
The net movement of electric charges in one direction.
Measured in units called amperes or amps.
Symbol for amperes is A.
Measures the electrons that flow past one point.
1 A = 6,250 million billion electrons moving past a point every second.

42. Voltage
The electric force that makes charges move.

43. Voltage The electric force that makes charges move.
Voltage is like the force that acts on water in a pipe.

44. Voltage The electric force that makes charges move.
Voltage is like the force that acts on water in a pipe.
Water flows from higher pressure to lower; likewise, electric charge flows from higher voltage to lower voltage.

45. Voltage difference
Related to the force that makes electric charges flow.

46. Voltage difference
Related to the force that makes electric charges flow.
Measured in units called volts (V).

47. Electric Circuit Closed loop-like path that current must follow.
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48. Electric Circuit Closed loop-like path that current must follow.
If the circuit is broken, current will not flow & bulb will not light.

49. Batteries
Provide the voltage difference that keeps electric current flowing in a circuit.

50. Batteries
Provide the voltage difference that keeps electric current flowing in a circuit.
The positive & negative ends are called terminals.

51. Batteries
Provide the voltage difference that keeps electric current flowing in a circuit.
The positive & negative ends are called terminals.
When a closed path connects the terminals, current will flow.

52. Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution
A. dry cell - use paste – flashlight battery
B. wet cell – use liquid – car battery

53. Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution
A. dry cell - use paste – flashlight battery
B. wet cell – use liquid – car battery
Photovoltaic – electrons move when light hits a material – calculators, solar panels

54. Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution
A. dry cell - use paste – flashlight battery
B. wet cell – use liquid – car battery
Photovoltaic – electrons move when light hits a material – calculators, solar panels
Thermoelectric – electrons move across two metals joined together & held at different temperatures – thermostats for ovens

55. Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution
A. dry cell - use paste – flashlight battery
B. wet cell – use liquid – car battery
Photovoltaic – electrons move when light hits a material – calculators, solar panels
Thermoelectric – electrons move across two metals joined together & held at different temperatures – thermostats for ovens
Piezoelectric – electrons move when opposite surfaces of crystals become charged under pressure – mikes, keyboards

56. Electrical outlets
Also give a voltage difference, usually higher than a battery, such as 120 V or 240 V for large appliances.

57. Resistance
The tendency for a material to oppose the flow of electrons, changing electric energy into heat and light

58. Resistance
The tendency for a material to oppose the flow of electrons, changing electric energy into heat and light.
Electrons flowing through the wire filament of a light bulb bump into metal atoms heating the filament until it glows lighting up…electric to thermal to radiant energy.

59. Resistance
The tendency for a material to oppose the flow of electrons, changing electric energy into heat and light.
Electrons flowing through the wire filament of a light bulb bump into metal atoms heating the filament until it glows lighting up.
Resistance turns electric energy into heat & light.

60. Resistance
is measured in units called ohms (Ω) or the Greek letter omega.

61. Resistance
is measured in units called ohms (Ω) or the Greek letter omega.
Temperature, length, & thickness of a material can affect its electrical resistance.

62. Resistance
is measured in units called ohms (Ω) or the Greek letter omega.
Temperature, length, & thickness of a material can affect its electrical resistance.
Hotter, longer & thinner – more Ω

63. a simple circuit requires
1. Source of voltage difference i.e. Battery
2. Device with resistance i.e. light bulb
3. Conductors i.e. wires connecting all three so that current can flow.

64. Ohm’s law
States that the current in a circuit equals the voltage difference divided by the resistance.

65. Ohm’s law
States that the current in a circuit equals the voltage difference divided by the resistance.
If I stands for electric current, Ohm’s law can be written as :
current (in amps) = voltage difference
resistance (in Ω)
I = V/ R or R = V/I

66. Problem
Suppose a current of 0.5 A flows in a 75-W light bulb. The voltage difference b/w the ends of the filament is 120 V. Find the resistance of the filament.

67. Problem
Suppose a current of 0.5 A flows in a 75-W light bulb. The voltage difference b/w the ends of the filament is 120 V. Find the resistance of the filament.
R = V/I = 120/0.5 = 240
The resistance is 240 Ω.

68. Electrical Energy
Chapter 7 section 3

69. Electrical energy
When you turn a hair dryer on, you close a circuit. EE turns into thermal energy & ME.
Voltage difference –
Resistance –
Conductor -

70. Electrical energy
When you turn a hair dryer on, you close a circuit. EE turns into thermal energy & ME.
Voltage difference – outlet
Resistance – hair dryer
Conductor - wires

71. Kinds of Circuits
Series –
Parallel -

72. Kinds of Circuits
Series – current has only one loop to flow through i.e. flashlights
Parallel -

73. Kinds of Circuits
Series – current has only one loop to flow through i.e. flashlights, some Christmas lights
Parallel – have at least two circuits for current to move through i.e. houses

74. Circuits
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75. Circuits
SERIES
PARALLEL

76. Parallel Circuits
Break up current lowering resistance.

77. Parallel Circuits Break up current lowering resistance.
More current flows through paths with less resistance.

78. Parallel Circuits Break up current lowering resistance.
More current flows through paths with less resistance.
Houses, cars and most electrical systems use parallel systems.

79. Household Circuits

80. Household Circuits
There is a main switch & a circuit breaker or fuse box.

81. Household Circuits
There is a main switch & a circuit breaker or fuse box.
Parallel circuits branch out from the circuit breaker or fuse box.

82. Household Circuits
There is a main switch & a circuit breaker or fuse box.
Parallel circuits branch out from the circuit breaker or fuse box.
The circuits run to wall outlets, appliances, & lights.

83. Fuses
Many appliances use current from the same circuit causing more heat in the wires.

84. Fuses
Many appliances use current from the same circuit causing more heat in the wires. To keep wires from causing a fire, household circuit include a fuse or circuit breaker.

85. Fuses
Many appliances use current from the same circuit causing more heat in the wires. To keep wires from causing a fire, household circuit include a fuse or circuit breaker.
A fuse is a small glass tube with a piece of metal inside that melts if the current is too high breaking the circuit.

86. Fuses
Many appliances use current from the same circuit causing more heat in the wires. To keep wires from causing a fire, household circuit include a fuse or circuit breaker.
A fuse is a small glass tube with a piece of metal inside that melts if the current is too high breaking the circuit.
To restore current, the fuse must be replaced.

87. Fuses
Using too many appliances at once is the main cause for a blown fuse.
You should turn off or unplug some appliances before changing the fuse.

88. Circuit Breaker
Switching device that prevents circuits from overheating by opening the circuit if the current is too high.

89. Circuit Breaker
Switching device that prevents circuits from overheating by opening the circuit if the current is too high.
You can reset the breaker by flipping the breaker box back to its original position but you should turn off or unplug some of the appliances first.

90. Electric Power
Rate at which electrical energy is changed into another form of energy.

91. Electric Power
Rate at which electrical energy is changed into another form of energy.
Different appliances use different amounts of energy and are usually marked with a power rating.

92. Electric Power
Rate at which electrical energy is changed into another form of energy.
Different appliances use different amounts of energy and are usually marked with a power rating.
Electric power (watts) = current (amps) X voltage difference (V) or P = IV
Power is usually measured in kilowatts (kW)

93. Electric energy calculation
Electrical energy (kW) =
electric power (kW) X time (hours)
or E = Pt
A 100 W light bulb left on for 5 h uses:
E = Pt = (0.1kW) (5h) = 0.5 kWh
If the power company charges 10 cents per kW, the cost of using the light would be 5 cents.

94. Cost of using Home Appliances
Hair dryer Stereo Color TV
Power rating 1,
Hours/day
Kwh /month
Cost / kWh $0.09 $0.09 $0.09
Monthly cost $0.68 $0.54 $2.16

95. Electric Fuse
Circuit Breaker
contains
contains
that
that
when
when
And makes the current

96. A piece of metal Electric Fuse Circuit Breaker contains contains that
Switches the circuit off
Can melt
when
when
It gets too hot
And makes the current
STOP