1 Unit C: Characteristics of Electricity(Physical Science: Physics) Sunday, December 03, 2017Sunday, December 03, 2017

2 Chapter 6 - Static electric charges collect on surfaces until given a path to escapeOutcomes Demonstrate and analyze characteristics of static electric charges and current electricity, including historical and cultural understandings Sunday, December 03, 2017Sunday, December 03, 2017

3 Static Electric ChargeA charge on a substance that stays in the same place

4 Examples of Static ChargeLightning- Static cling-

5 Examples of Static ChargeStatic shock-

6 6.1 The Characteristics of Static Electric Charges Solid materials are charged by the transfer of electrons Rubbing a balloon with your hair does not create electrical charges. All matter has electrical charges they are just normally neutral (equal protons/positive and electrons/negative). The rubbing transfers the electric charges from one object to another this phenomenon is called static electricity the study of static electricity is called electrostatics. Sunday, December 03, 2017Sunday, December 03, 2017

7 There are two types of electrical charges: positive and negative Electric Charge There are two types of electrical charges: positive and negative If something is positive it has lost electrons. If something is negative it has gained electrons. Charging an item by “rubbing” transfers electrons making something electronically charged. Sunday, December 03, 2017Sunday, December 03, 2017

8

9 Laws of Electric ChargeUnlike charges attract one another Like charges repel one another Charged objects attract neutral objects

10 The Law of Electric Charges A Model for the Electrical Nature of Matter Model of the Atom Sunday, December 03, 2017Sunday, December 03, 2017

11 There are three ways for something to be electronically chargedFriction Contact Induction Sunday, December 03, 2017Sunday, December 03, 2017

12 Producing Static ElectricityCharge by Friction Electric charge is transferred by rubbing object together Friction can remove electrons from an object

13 Producing Static ElectricityWe know which object will cause which charge when caused by friction using the Electrostatic Series Table 6.2 p. 208 (Items above become negatives) Rubber Ebonite Polyethylene cotton silk wool glass acetate fur/hair (Items below become positives)

14 Insulators An electrical insulator is a substance in which electrons cannot move freely from atom to atom. Conductors A conductor is a substance in which electrons can move freely from one atom to another. Sunday, December 03, 2017Sunday, December 03, 2017

15 Static Electricity and WinterStatic electricity is much worse in the winter because the air is so dry and dry air is a very good insulator. Water droplets transfer electrons very easily and do not allow large charges to build up. Read Pages Learning Checkpoint p. 209 # 1 - 5 6.1 Check and Reflect # 1 – 7 (p. 211) Sunday, December 03, 2017Sunday, December 03, 2017

16 6.2 The Transfer of Static Electric ChargesIn charging by contact, a neutral object gains the same type of charge as the charged object touching it. In charging by induction, a neutral object gains the opposite charge as the charged object DIAGRAM Sunday, December 03, 2017Sunday, December 03, 2017

17 Charging By Contact A charged item can transfer its charge by touching a charged or even an uncharged item. Sunday, December 03, 2017Sunday, December 03, 2017

18 Removing Static ElectricityDischarge (neutralize)- When excess electric charge is removed from an object. Discharge can be quick and explosive (lightning) Discharge can be unnoticed (fabric softener sheet)

19 Removing Static ElectricityGrounding Connecting the object to the earth The charge is shared with the entire earth Discharge at a point Objects made into a point have electrons pushed off the end.

20 Induction - something is made to happen without contactInduced Charge Separation A slight shift in position of electrons that produces opposite charges on the two sides of a particle Sunday, December 03, 2017Sunday, December 03, 2017

21 Producing Static ElectricityCharge by Induction Neutral object becomes charged when a charged object is brought near it. Induced charge can become more permanent if a ground wire is attached to it.

22 Charging Conductors by InductionIt is possible to induce a charge on a conductor and even give it a permanent charge. Sunday, December 03, 2017Sunday, December 03, 2017

23 Read Pages 213 - 219 6.2 Check and Reflect # 1 – 9 (p. 219) Sunday, December 03, 2017Sunday, December 03, 2017

24 Detecting Static ChargeElectroscope -a device used to detect the presence of charge. usually constructed with a metal plate or sphere at the top of a metal post with thin foil leaves hanging from the bottom of the post

25

26 6.3 Electrostatics in Our LivesSome First Nations and Métis peoples have an intimate spiritual understanding of lightning in terms of Thunderbird Lightning rods are used to prevent damage to buildings Sunday, December 03, 2017Sunday, December 03, 2017

27 Dangers of Static ElectricityCause fires https://www.youtube.com/watch?v=tuZxFL9cGkI Can wreck electronics (need grounding wire) Can hurt (shock) or cause death (10-9)

28 Uses of Static ElectricityElectrostatic air cleaners Removes dust and other particles by the attraction of unlike charges Electrostatic spray painting The paint and the object to be painted are given opposite charges

29 Uses of Static ElectricityFabric softener sheets Allows electric charge to move in between clothes instead of building up. Photocopiers Cell phones and car radios

30 Electrostatic precipitators work by creating charged waste particles and using electrostatic attraction to remove particles Sunday, December 03, 2017Sunday, December 03, 2017

31 Discharge at a Point For items that are not attached to the earth like an air plane grounding will not work. Airplanes use a method of discharging at a point of a rod which effectively discharges a charge very quickly. Sunday, December 03, 2017Sunday, December 03, 2017

32 6.3 Check and Reflect # 1 – 11 (p. 228) Read Pages 6.3 Check and Reflect # 1 – 11 (p. 228) Chapter 6 Review p. 232 – 233 # Sunday, December 03, 2017Sunday, December 03, 2017

33 Chapter 7 – Current electrical energy is the flow of electrons in a closed circuitOutcomes Demonstrate and analyze characteristics of static electric charge and current electricity, including historical and cultural understanding Analyze the relationships that exist among voltage, current, and resistance in series and parallel circuits Sunday, December 03, 2017Sunday, December 03, 2017

34 7.1 Voltage, Current, and Resistance Static Electricity is the build up of electrons and the transfer of an electrical charge. The flow or movement of electric charges from one place to another is called electric current. Sunday, December 03, 2017Sunday, December 03, 2017

35 Current Electricity The movement of electric charge from one place to another.

36 Electric current is the rate of movement of electric charge through a conductor.The electric current passing through your house is different than static electricity it is flowing through a controlled path called an electric circuit. Electric circuits are used to convert electrical energy into other forms of energy we need. Sunday, December 03, 2017Sunday, December 03, 2017

37 Voltage Potential (Voltage)-IS THE ELECTRIC POTENTIAL PER CHARGE MOVING BETWEEN TERMINALS. THIS IS LIKE THE ELECTRIC PRESSURE PUSHING THE ELECTRONS. VOLTAGE DOES NOT MOVE, IT PUSHES THE ELECTRONS.

38 Electric Potential (Voltage) Voltage is the difference in electric charge between two points The energy each electron has is called the electric potential of the electron. The unit used to measure electric potential is the volt. Pump Analogy Voltage can be compared to the pressure of water in a hose. The higher the pressure, the faster the water will flow through the hose. Similarly, the higher the voltage of the electricity, the faster it will flow from a source of electricity to an end use. Sunday, December 03, 2017Sunday, December 03, 2017

39 High Voltage Low Voltage

40 High Voltage Low Voltage

41 Voltage Potential (Voltage) cont’d- Measured in volts (V)Measured using a voltmeter.

42 Electric Current Electric current is a measure of the rate at which electric charges move past a given point in a circuit. The unit used to measure electric current is ampere. Sunday, December 03, 2017Sunday, December 03, 2017

43 Current Current- The measure of the rate at which electric charges move past a given point in a circuit. Measures the amount of electricity passing a point. Measured in amperes (A) Measured using an: Ammeter- larger currents Galvanometer- smaller currents

44 Amps can be compared to the volume of water that flows through a hoseAmps can be compared to the volume of water that flows through a hose. The volume of water that flows past a certain point in a specific amount of time can be measured. The rate of the electric current is dependent upon the voltage and resistance. A circuit with high voltage and low resistance will have more amps (greater number of electrons passing through the circuit) than a circuit with low voltage and higher resistance. Sunday, December 03, 2017Sunday, December 03, 2017

45 High Current Low Current

46 High Current Low Current

47 Resistance ResistanceThe measure of an objects opposition to the passage of a steady electrical current Measured in ohm’s (Ω) Measured using an ohmmeter

48 Electrical Resistance and Ohm’s Law The ability to impede the flow of electrons is called electrical resistance. A resistor is used for this purpose. Electrical resistance R is measured in ohms. Sunday, December 03, 2017Sunday, December 03, 2017

49 Low Resistance Low Resistance High Resistance

50 Electrochemical Cell An electrochemical cell generates electricity by creating an imbalance of charges between terminals Primary Cells Primary cells use materials in a chemical reaction to create electricity. Sunday, December 03, 2017Sunday, December 03, 2017

51 Primary cells- Disposable cellsSecondary cell- reusable cells All cells contain: Electrodes- Metal plates that are placed in the electrolyte Electrolytes- Chemicals that conduct electric current Positive terminal- Place where positive charges collect Negative terminal- Place where negative charges collect

52 A primary wet cell or voltaic cell use two metals (usually copper and zinc) as electrodes and use a liquid (sulphuric acid) as an electrolyte. Copper gives its electrons to zinc and when connected the electrons are allowed to flow. Sunday, December 03, 2017Sunday, December 03, 2017

53 Electrical Sources Cells can be: Wet cells- electrolyte is a liquidEasy to make with available chemicals Hard to transport and quite large Electrodes Electrolyte

54 Electrical Sources Dry cells- Electrolyte is a pasteEasy to transport and very compact; sealed Special and sometimes more dangerous chemicals are required.

55 Learning Checkpoint p. 242 # 1 - 5 Secondary Cells A secondary cell can be discharged and recharged because it does not use chemicals. Models can be mental, mathematical, or a combination. Scientific models can help you communicate your ideas. Read Pages Learning Checkpoint p. 242 # 1 - 5 7.1 Check and Reflect # 1 – 14 (p. 244) Sunday, December 03, 2017Sunday, December 03, 2017

56 7.2 Series Circuits and Parallel CircuitsSunday, December 03, 2017Sunday, December 03, 2017

57 Electrical circuits Electrical circuit- Contain 4 partsControlled path of flowing electricity in a complete circle Contain 4 parts Source- Where electricity comes from. Load- Where the electrical energy is transferred. Control- What starts and stops the electricity. Connectors- The path where the electricity runs.

58 Load Source Control Connector

59 Electrical circuit- SourceCells- Converts chemical energy into electrical energy. Batteries- combination of 2 or more cells Generators-a device that converts movement into electrical energy Photoelectric cells- a cell that converts light directly into electrical energy

60 Cell Battery Generator Photoelectric Cell

61 Lamp/bulb – An electrically energized source of light Electrical Load An electrical load is anything that converts electrical energy into any form of energy we need. Resistor – circuit component designed to provide a specific amount of resistance to current flow. Lamp/bulb – An electrically energized source of light Motor – A device or machine that converts other forms of energy into mechanical energy. Electric to mechanical Sunday, December 03, 2017Sunday, December 03, 2017

62 Electric circuit- LoadAnything that converts electrical energy into the form of energy required Light bulb (light energy) Toaster (heat energy) Television (light and sound energy) Computer (light and sound energy) Fan (mechanical energy) Music player (sound energy) Motor (mechanical energy)

63 Fuse – A safety device with a metal wire or strip that melts when the current gets too strong, cutting off the flow of the electrical current. Circuit Breaker – an additional safety device with a metal that does not melt but instead bends which triggers a mechanism that that turns of the flow of electrical energy In a short circuit, the current does not take the intended path back to its source Sunday, December 03, 2017Sunday, December 03, 2017

64 Electric Circuit Control Device Switch – used to open or close a circuit Timer and Thermostat Ammeter – measures current flow An ammeter is hooked up in series to measure current. Voltmeter – measures current pressure A voltmeter is hooked up in parallel to measure voltage Sunday, December 03, 2017Sunday, December 03, 2017

65 Electrical circuits-ConnectorsA conducting wire that provides a controlled path for electric current to flow to each part of the circuit Conductor- A substance where electrons can move freely from one atom to another. (electric current) Insulator- A substance where electrons cannot move freely from one atom to another. (Static electricity) Superconductor- Ceramics that conduct electricity with no resistance at low temperatures. (bullet trains)

66 Conductor e e e e Insulator e e e e e Superconductor e e e e

67 Electrical circuits Open circuit- circuit is not connected, switch is open, no electricity is flowing Closed circuit- circuit is connected, switch is closed, electricity is flowing Short Circuit- Circuit where there is not a load attached to the circuit, no resistance. Can be very dangerous, connectors can become overheated and burn, cells will use up the potential very rapidly.

68 Closed Circuit Open Circuit

69 Short Circuit

70 Electric Circuit Diagrams A circuit diagram is a model of an electric circuit Using the known symbols for some common electrical components a schematic circuit diagram can be used to illustrate a circuit. Example: Simple Circuit Four basic parts – load / conducting wire / electrical source / control (switch) Sunday, December 03, 2017Sunday, December 03, 2017

71 Electrical circuits Electrical circuits can be made in two different ways. Series circuit- One path of electric charge

72 Electrical circuits Parallel circuit- 2 or more paths for electric charge to follow (branches)

73 - Voltmeter - Cell V - Battery (2 cells) - Ammeter A - Light - Switch (1 pole) - Motor M

74 Making a Circuit Schematic DiagramCreate a circuit that has one cell powering 1 light that is controlled by a switch.

75 Create a circuit with a 3 cell battery that has 2 lights connected in series all controlled by one switch.

76 Create a circuit with a 3 cell battery that has 2 lights connected in parallel all controlled by one switch, with another switch controlling just one of the lights.

77 Cells in Series and Parallel Cells in series are connected end-to-end and have an additive voltage. Pump Analogy Series Circuit – all components are connected end-to-end, forming a single path for electrons to flow. In a series circuit, the current is constant and the voltages across resistors adds up to the total voltage supplied by the energy source Sunday, December 03, 2017Sunday, December 03, 2017

78 Electrical circuits Connecting cells in:Series- the potentials of the cells are added together ie. Three 1.5V cells connected end to end has a potential of 4.5V + + + - - - = 4.5 V

79

80 Adding resistance increases the total resistance and lowers current Current is the same throughout the circuit The total resistance is the sum of the resistances in the circuit Example Three 1.5V cells an ammeter and three resistors (R1= 4 Ω, R2= 5 Ω, and R3=6 Ω) in series What is the total resistance? What is the total voltage? Sunday, December 03, 2017Sunday, December 03, 2017

81

82 Cells in parallel are not connected end-to-end and thus do not have an additive voltage instead they are connected beside each other and have twice as many electron doing one cells work. Pump Analogy Parallel Circuit – all components are connected across each other, forming exactly two sets of electrically common points. In a parallel circuit, the voltages across loads are constant and the currents on each path add up to the total current leaving the energy source Sunday, December 03, 2017Sunday, December 03, 2017

83 Electrical Circuits Parallel- the cells will last longer + + + - - -Potential remains the same + + + - - - = 1.5V

84

85 Adding resistance decreases the total resistance and increases current The more branches there are the smaller the resistance in each branch, the more the total circuit current will be (additive) Voltage remains constant and is equal to the source Sunday, December 03, 2017Sunday, December 03, 2017

86 Example Three 9 V cells in parallel attached to a switch and an ammeter in series attached to three resistors and a voltmeter in parallel (R1= 4 Ω, R2= 5 Ω, and R3=6 Ω) What is the total voltage? Sunday, December 03, 2017Sunday, December 03, 2017

87

88 Each load uses a portion of the total energy supplied by the battery Circuit Voltage (volts) Current (amps) Resistance (ohms) Series Circuit Each load uses a portion of the total energy supplied by the battery The current is the same throughout the circuit The current decreases when more resistors are added if the energy remains the same Parallel Circuit Each load uses all the energy supplied by the battery The current divides into different paths. A pathway with less resistance will have a greater current Adding resistors in parallel decreases the total resistance of the circuit if the energy remains the same Sunday, December 03, 2017Sunday, December 03, 2017

89 Electrical circuits Pro’s and cons of series and parallel circuits.Simple to make and easy to follow. Con’s Limited control over the circuit and when one load is broken, the entire circuit won’t work.

90 Electrical circuits Pro’s and cons of series and parallel circuits.Lots of control over the circuit and not all loads have to be working at the same time Con’s Much more complex and difficult to follow.

91 7.2 Check and Reflect # 1 – 9 (p. 253)Read Pages 7.2 Check and Reflect # 1 – 9 (p. 253) Sunday, December 03, 2017Sunday, December 03, 2017

92 7.3 Ohm’s Law Ohms (Ω) measure resistance and can be compared to the diameter measurement of a hose. A smaller diameter hose will allow less water to flow through than a larger diameter hose. Similarly, a thinner wire increases resistance, causing a lesser amount of electricity to be transmitted because it is encountering resistance in the wire. To reduce resistance, certain metals are used to conduct electricity, such as copper, which allows electrons to flow easily. Sunday, December 03, 2017Sunday, December 03, 2017

93 When electrons flow through a conductor electrical resistance causes a loss of electrical potential (volts). This loss is referred to as potential difference. Sunday, December 03, 2017Sunday, December 03, 2017

94 Ohm’s Law “the potential difference between two points on a conductor is proportional (directly related) to the electric current flowing through the conductor” We refer to potential difference as voltage drop b/c voltage is lost or “dropped” across a conductor. Sunday, December 03, 2017Sunday, December 03, 2017

95 We can calculate voltage drop by:Potential difference (voltage drop) = electric current x Electrical Resistance V = I x R Potential difference (V) is measured in volts (V) Electric current (I) is measured in amperes (A) Electrical Resistance (R) is measured in ohms (Ω) Ohm’s Law V = I x R, describes the relationship between voltage, current and resistance Sunday, December 03, 2017Sunday, December 03, 2017

96 Solving Science Problems Involving Formulas 5 step process Data – record the given and required data Formula – write the required formula Substitute – place the data in the formula Calculate – do the math (calculator) Statement – write a sentence to paraphrase your work Sunday, December 03, 2017Sunday, December 03, 2017

97 Example Problem 7. 1 A current of 4Example Problem 7.1 A current of 4.0 A flows through a 40 Ω resistor in a circuit. Calculate the voltage. Example Problem 7.2 A 30 V battery generates a current through a 15 Ω resistor. How much current does the battery generate? Example Problem 7.3 An electric stove is connected to a 240 V outlet. If the current flowing through the stove in 20 A, what is the resistance of the heating element? Sunday, December 03, 2017Sunday, December 03, 2017

98 What is the total resistance? What is the total voltage? Example Three 1.5V cells, a switch, an ammeter and three resistors (R1= 4 Ω, R2= 5 Ω, and R3=6 Ω) in series What is the total resistance? What is the total voltage? What is the current for this circuit? What is the voltage drop for each resistor? Sunday, December 03, 2017Sunday, December 03, 2017

99 What is the total voltage? What is the current through each resistor? Example Three 9 V cells in parallel attached to a switch and an ammeter in series attached to three resistors and a voltmeter in parallel (R1= 4 Ω, R2= 5 Ω, and R3=6 Ω) What is the total voltage? What is the current through each resistor? What is the total current? What is the total circuit resistance? Sunday, December 03, 2017Sunday, December 03, 2017

100 Practice problems p. 260 – 261 (3) Read Pages 258 - 264 7.3 Check and Reflect # 1 – 6 (p. 264) Chapter 7 Review p. 266 – 267 # Sunday, December 03, 2017Sunday, December 03, 2017

101 Chapter 8 – We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy Outcomes Assess operating principles, costs, and efficiencies of devices that produce or use electrical energy Critique impacts of past, current, and possible future methods of small and large scale electrical energy production and distribution in Saskatchewan Sunday, December 03, 2017Sunday, December 03, 2017

102 Energy Energy- The ability to do work. There are many forms of energyLight Sound Movement (mechanical) Heat Electricity Nuclear Chemical

103 Thermodynamics Thermodynamics is the study of moving energy.The first law of Thermodynamics says that: Energy cannot be created or destroyed. Energy can only be transformed from one form to another.

104 Electricity Light

105 Energy TransformationsToaster- Electrical energy is converted to heat energy. The heat is produced by resistance inside the toaster (friction) Electricity Heat

106 Energy TransformationsLight Bulb- Electrical energy is converted to light energy Light is produced by the resistance inside the light bulb. Electricity Light

107 Energy TransformationsSpeaker- Electrical energy is converted into sound energy. Sound is produced by having electricity turn a magnet on and off. (electromagnet) Electricity Sound

108 Energy TransformationsElectric motor- Electrical energy is converted into motion (mechanical) energy. Motion is produced by creating an alternating magnetic field. (electromagnet) Electricity Motion

109 Electromagnets A coiled wire carrying electrical current produces a magnetic field around it. It acts like a magnet. N S

110 Electromagnets If a piece of metal is inserted into the coil, the metal will become magnetized. The magnetism will only last when electricity is running through the circuit.

111 N S With an open circuit, there is no magnetic field.With a closed circuit, there is an electric field. N S

112 Electromagnet Metal plate

113 N S Running electricity through a wire coil produces a magnetic fieldPermanent Magnet Brushes N The similar poles ‘repel’ each other causing the wire coil to rotate. When the gap in the wire coil reaches the brushes, the magnetic field disappears. The wire coil will continue to rotate in the same direction, which will produce a new magnetic field in the same direction. S Wire coil This process continues producing a continuously rotating coil.

114 Thermodynamics The second law of thermodynamics tells us that every time energy is transformed from one type of energy to the next type, some of the energy is transformed into an unusable form. Not all the energy is converted.

115 Electricity Light Sound Heat

116 Electricity Heat Energy LossToaster- Electrical energy is converted to heat energy. Energy is lost in the production of light and sound. Light Electricity Heat Sound

117 Electricity Light Energy LossLight Bulb- Electrical energy is converted to light energy Energy is lost as heat Heat Electricity Light

118 Electricity Sound Energy LossSpeaker- Electrical energy is converted into sound energy. Energy is lost as heat and motion. Heat Electricity Sound Motion

119 Electricity Motion Energy LossElectric motor- Electrical energy is converted into motion (mechanical) energy. Energy is lost as heat and sound. Heat Electricity Motion Sound

120 Generating electricityWe have discussed several sources of electrical energy; Cells Batteries Photoelectric cell Generator

121 Generating electricityThe majority of our daily electricity comes from electricity generating stations. All generating stations work on the same principals. We discussed earlier how current electricity in a coil produces a magnetic field. The reverse process is used to produce current electricity. A moving magnetic field produces current electricity.

122 S N In the presence of a magnet, the electrons are drawn in by the magnetic field. e e e e e e e e e e e e e e e e When the magnet moves, the electrons will be pulled along with it. The electrons are now moving, this is current electricity.

123 Generating electricityA generator uses the same materials as an electric motor, but everything happens in reverse. Electric motor- current electricity produces the spinning coil. Generator- a spinning coil produces current electricity

124 The electrons are drawn to one side of the magnet so the electrons flow in one direction to that side of the magnet. N As the coil rotates, the electrons are again drawn to the one side of the magnet so the electrons make the trip again e e e e e e e e e e e e e e e e As the coil continues to rotate, current electricity continues to flow. S

125 Generating ElectricityThere are two types of electricity that can be created: Direct current (DC)- Electricity flows in one direction (cells, generator shown) Alternating current (AC)- Electricity switches directions as the coil rotates.

126 Alternating Current (AC)Direct Current (DC) e e e e Alternating Current (AC) e e e e e e e e

127 Generating ElectricityThere are many different ways to turn the wire coil inside the generator. The coil is attached to a turbine, and the turbine is rotated by: Steam (coal, nuclear, natural gas, biomass) Water Wind

128 Transporting ElectricityElectricity has to be moved from the generating stations to peoples houses.

129 From these substations, electricity in different power levels is used to run factories, streetcars and mass transit, light street lights and stop lights, and is sent to your neighborhood. The high voltage electricity is then carries by thick transmission cables made of copper or aluminum. Copper and aluminum are used because of their low resistance. In your neighborhood, another small transformer mounted on pole or in a utility box converts the power to even lower levels to be used in your house. The power lines go into substations near businesses, factories and homes. Here transformers change the very high voltage electricity back into lower voltage electricity. The electricity is then moved to a transformer at the power plant which boosts the voltage to V. Electricity travels more efficiently at higher voltages. Most large scale generators produce around V of electricity.

130 Electricity that comes into our homes has been reduced to around 240 V.Older homes have the electricity brought in by overhead lines, newer homes have underground lines. After passing through the power meter it enters the house through the breaker box. There is one main breaker switch that controls all the electricity in the house. A breaker is a safety device that shuts the power off if the current becomes to high. Inside the breaker box, the electricity can be kept at 240 V for some appliances (Oven, Furnace, etc.) or reduced to 120 V for lights and plugs. Each circuit in the house is controlled by a separate cicuit breaker. Before the electricity is brought into your house, it is passed through a power meter to record the amount of electricity being consumed. Main breaker switch Individual circuit breakers

131 E.g. Solar, wind, biomass, hydroelectric, geothermal, tidal8.1 Renewable and Non-Renewable Energy Resources for Generating Electrical Energy Renewable Energy Resources – resources that constantly replenish themselves E.g. Solar, wind, biomass, hydroelectric, geothermal, tidal Non-renewable Energy Resources – resources that cannot be replaced in a reasonable amount of time E.g. Fossil fuels (oil/coal) and nuclear Sunday, December 03, 2017Sunday, December 03, 2017

132 We need to move toward sustainability in our resources Sustainability – with respect to electrical energy refers to a consideration of social, economic, and environmental aspects of its production and use now and in the future We need to move toward sustainability in our resources Electrical energy generators transform the energy of motion into electric current Read Pages Learning Checkpoint p. 276 # 1 – 3 Learning Checkpoint p. 277 # 1 – 3 8.1 Check and Reflect # 1 – 9 (p. 280) Sunday, December 03, 2017Sunday, December 03, 2017

133 8.2 Reducing Our Electrical Energy ConsumptionMaking the Most of Energy Resources Input energy – chemical energy used to make electricity Output energy – actual electric energy produced Efficiency = useful energy output / energy input % efficiency = useful energy output / energy input x 100% Sunday, December 03, 2017Sunday, December 03, 2017

134 Efficiency Efficiency is the comparison between the amount of useful energy produced (output energy) and the original amount of energy used (input energy). % efficiency = Useful Output Energy x 100% Input Energy

135 Example Determine the percent efficiency of a bulb that uses 2000 J of electrical energy to produce 400 J of light energy. Sunday, December 03, 2017Sunday, December 03, 2017

136 Can you ever have an appliance than is 100% efficient?No

137 Electrical Energy Use in the Home Electrical Energy = Electrical Power x time interval E = P x Δt E = kW∙h (Electrical energy consumption is usually measured in kilowatt-hours) P = kW Δt = h Sunday, December 03, 2017Sunday, December 03, 2017

138 Example How many kilowatt hours of electrical energy are used in one month by a clothes dryer that has a power rating of 5 kW and is operated for 4.5 h? Sunday, December 03, 2017Sunday, December 03, 2017

139 Cost = Electrical Energy (kW∙h) x rate (cost per kW∙h)Example Calculate the cost of the electricity needed to operate a refrigerator/freezer (500 W) for one month if it uses 75 kW∙h of energy. The rate charged for electricity is $0.08 / kW∙h. Sunday, December 03, 2017Sunday, December 03, 2017

140 Learning Checkpoint p. 286 # 1 Practice Problems # 1 – 3 p. 287 The EnerGuide label shows how much energy an appliance will use in a month of average use Energy Star appliances are the most efficient appliances in their class Read Pages Learning Checkpoint p. 286 # 1 Practice Problems # 1 – 3 p. 287 8.2 Check and Reflect # 1 – 13 (p. 290) Sunday, December 03, 2017Sunday, December 03, 2017

141 Measuring Electrical Energy Energy – the ability to do work Electrical energy (E) – energy transferred to any electrical load by moving electric charges Electrical energy is measured in joules. A joule is a small amount ~ light a 100 W bulb for 1 / 100th of a second Also measured in Watt hour which is 3600 times as much as a joule or kilowatt (1000 W) Sunday, December 03, 2017Sunday, December 03, 2017

142 Calculating Electrical Energy E = V x I x Δt where E – electrical energy measured in Joules (J) for seconds or Watt hours (W∙h) for hours V – voltage drop measured in volts (V) I – electric current measured in amps (A) Δt – time interval measured in seconds or hours Sunday, December 03, 2017Sunday, December 03, 2017

143 Example Calculate the energy released from a battery in a flash light that was on for 4.5h with a voltage of 6V and a current of 0.35 amps. Sunday, December 03, 2017Sunday, December 03, 2017

144 The Rate at Which Energy is Used Electrical Power (P) – measure at which electrical energy is used measured in watts Electrical power = electrical energy / time interval P = E / Δt Sunday, December 03, 2017Sunday, December 03, 2017

145 P = E / Δt = V x I x Δt / Δt = V x IExample Calculate the power of a toaster that uses J of energy for 50s Or P = E / Δt = V x I x Δt / Δt = V x I Calculate the power of a vacuum cleaner if the operating voltage is 120 V, and the current flowing through it is 7.90 amps Sunday, December 03, 2017Sunday, December 03, 2017

146 Hand-Out – Electricity Calculations Chapter 8 Review P. 294 – 295 # 1 – 21 Unit C Review P. 299 – 301 # Sunday, December 03, 2017Sunday, December 03, 2017