1 Electrical Principles and TechnologiesScience 9 Unit D

2 Electrical Energy can be Transferred & StoredElectrical Charges can be described as ‘Unbalanced charges’ because there is a build up and than it is discharged

3 To understand electricity we must start with the atom. Static Electricity To understand electricity we must start with the atom. All matter is composed of atoms.

4 The Atom The atom consists of three particles:Electrons have a negative charge Neutrons carry no charge Protons have a positive charge These charges cause either an attractive or repulsive force between particles

5 Sub Atomic Particles Protons and Neutrons are found in the nucleus of the atom Electrons orbit the nucleus and are free to be removed

6 Electrical Charge 1. Neutral or Uncharged: 2. Positively ChargedMost matter exists in this state The number of protons (+) and electrons (-) are equal (balanced) so there is not a charge 2. Positively Charged There are more protons (+) than electrons (-) so the charge is unbalanced and positive Electrons have left 3. Negatively Charged There are more electrons (-) than protons (+) so the charge is unbalanced and negative Electrons have been added

7 Static Electricity Most objects are neutral – equal positive and negative charge Charged objects have more or less electrons than neutral objects

8 Static Electricity Forces of attractionOpposite charges attract Like charges repel A charge separation occurs when a charged object is brought near to a neutral object

9 Charge Separation When a charged object is brought near a neutral object, the law of charges will determine what will happen Example: A negatively charged balloon approaching a wall Electrons in the wall will be repelled by the negative balloon An area of positive charge will be created The balloon and wall will be attracted

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11 Static Electricity Electrical discharge (release) can occur when a charge experiences a force great enough to “jump” across a gap

12 Lightning – static electricity in the air discharges to the Earth’s surfaceNova Video – Lightning [Lightning H/O]  Tesla

13 The Laws of Electrical ChargeThese laws describe what happens when two charged particles or objects are brought close together. 1. Opposite charges attract each other 2. Like charges repel each other 3. Charged objects attract uncharged (neutral) charges

14 Neutralizing Unbalanced ChargesNeutralizing is the balancing of a charge This can be seen as electrical discharge A shock or spark that results in a gaining or loss of electrons to become balanced or neutral Grounding is another way to balance charges A wire is attracted to a large object (many times the Earth) as an easy way to neutralize a charged object

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17 Your Task Check & Reflect p 278 # 1 - 9

18 If You Are Having Difficulties… zU&feature=related el

19 Current Electricity Electricity in motion

20 So What Does It All Mean? Current Electricity: is a continuous flow of electrons from an energy source Circuit: Uninterrupted flow of electrons in a complete path

21 Introduction to CircuitsCircuits generally consist of four main components: Power Supply Conductor Load Switch *Note that all circuits DO NOT have to have ALL of these components

22 Conductor – a material that will let electrons flowCurrent Electricity Conductor – a material that will let electrons flow Most metals are conductors Insulator – a material that resists the flow of electrons Most non-metals are insulators

23 Current Electricity Electricity can flow when it has a complete circuit and an energy source

24 Current Electricity Measuring Current Ampere (A) – measure of the number of electrons passing a point each second

25 Larger currents are measured with an ammeter.An instrument used to measure very weak electric current is called a galvanometer. Larger currents are measured with an ammeter.

26 Ammeter An ammeter is connected in series (all current must flow through the device)

27 Current Electricity aka potential differenceElectrical energy is measured in volts (V) aka potential difference Voltage is a measure of how much electrical energy each charged particle carries.

28 Voltmeter – a device to measure potential difference (voltage)Current Electricity Voltmeter – a device to measure potential difference (voltage)

29 Voltmeter A voltmeter is connected in parallel (to either side of a load to measure potential difference drop)

30 Did You Know? A current with an amperage as little as 0.1A is felt as a shock but a current of 1.0A is deadly.  Voltage jolts, but amperage kills

31 Resistance Resistance: Limits the flow of electricityExpressed in Ohms ( Ω )

32 Affected by voltage and amperageHigh voltage means high resistance voltage = resistance Direct Relationship High amperage means low resistance amperage (I) = resistance Indirect Relationship High temperature means more resistance Temperature= resistance

33 Your Task Check & Reflect p 283 #

34 Electrical Safety PROTECT YOURSELF!

35 Voltage and amperage both play a role in whether electricity can killA significant electric shock, that is not fatal, can still cause serious and long term damage or injury to your body and nervous system

36 Electrical Safety Short Circuit: Current bypasses normal circuit and takes the shortest route Downed power lines will allow the electricity to move outside the circuit

37 Insulators vs. ConductorsRubber soled shoes or car tires may provide some protection from a shock Other substances may come into play, wet or damp soil will conduct better than dry soil Example if you touch an electric fence on a dry day, the shock will be less than the same fence on a damp day with muddy ground Current flow (A) is what makes electricity dangerous

38 Protect Yourself Never handle electrical devices when you are wet or around water Don’t use any power cord that is frayed Always unplug before tampering Don’t stick items in power outlets Don’t overload circuits Stay away from power lines Don’t bypass safety features Pull on the plug not the cord Never remove the third prong

39 Electrical Safety Fuses & Breakers – devices that will break a circuit if it becomes overloaded (ie. too much current flowing) [Read p 286]

40 Fuses A device with a metal strip having a lower melting point than the wire it is connected to The metal strip melts before the wire overheats This causes a break in the flow of electricity A fuse cannot be reused

41 Circuit Breaker Have a special metal that triggers a spring if too much electricity passes through The surge produces heat that causes the strip to bend (Flips the breaker and breaks the circuit)

42 3 Prong Plugs 3-prong plugs provide an alternative way for the electricity if there is a short 3rd prong is a ground wire  carries an overload of current away from the circuit Ground Wire

43 Your Task Check & Reflect p 287 #

44 Cells & Batteries Wet Cells & Dry Cells

45 A cell or battery converts chemical energy into electrical energyCells and Batteries Cells or Electrochemical cells are made up of several chemicals to produce a steady supply of electricity A battery is made when one or more cells are connected together A cell or battery converts chemical energy into electrical energy IMPORTANT: One is ALWAYS a CELL. A BATTERY is made up of TWO or MORE CELLS

46 Electrochemical CellsTwo metal electrodes (2 different metals) are surrounded by an electrolyte (paste or liquid) Anode/Cathode

47 Cells & Batteries Dry Cells – chemicals in a paste transfer electrons from the negative terminal through the conductor and load then back to the positive terminal

48 Cells & Batteries Remember that electrons leave from the negative electrode and return to the positive electrode

49 Cells & Batteries Wet Cells – use a liquid electrolyte (acid) to allow transfer of electrons between the positive and negative electrodes

50 Primary Cell – a non-rechargeable battery

51 Cells & Batteries Rechargeable cells (secondary cells) – electrical energy is used to push electrons back to the source electrode

52 Cells & Batteries A cell is a single set of electrodes and an electrolyte while a battery is a series of cells connected together [Note: What we call batteries are not all batteries]

53 Cells & Batteries ElectroplatingUsing a thin coating of a desired metal to coat less expensive metals

54 Your Task Check & Reflect p 294 # 1-10 Section Review p 295 # 1 – 10

55 Technologies to Control the FlowRead Key Concepts p 296 Read p 296

56 Unique Circuits and ConductivityA characteristic of a non-metal is that they do not conduct electricity Neon signs are a glass tube filled with a noble gas The atoms are excited by the current and this causes the electrons to become free. As these excited electrons move back into orbit, energy is released as light

57 Controlling the Flow Conductors – electrons are not tightly bound and thus can flow easily when voltage is applied Example: copper wire or other metals Insulators – electrons are tightly bound to the nucleus and resist movement when voltage is applied Example: Plastic, rubber or glass Note Fig 2.2 p 298

58 Electron Flow Though a ConductorAs soon as electrons are “pushed” into one end of a conductor the electrons already in the conductor begin to move

59 Quiz Time!!!!!

60 What are the three subatomic particleWhat are the three subatomic particle? Include their charge, symbol and where they are located. Like charges while opposite charges Explain what happens when a charged balloon is brought to a wall. You may use a diagram to help you explain. What are the 4 parts of a circuit? Draw an ammeter in a circuit What are the three parts of a cell? What is the difference between a wet and dry cell?

61 Resistance No conductor is a perfect conductor – there is always some resistance to electron flow that results in a loss of energy (heat, light) When electrons meet resistance to flow energy is dissipated by the emission of light or heat Resistors heat up Draw a lightbulb

62 Models of Resistance & Current Read p 305A long thin pipe (wire) will have more resistance than a large or short pipe (wire) Current slows as resistance increases

63 Modeling Current and ResistanceIf the pipe is large, the resistance to flow in the pipe is low The flow of water is greater This models great current If the pipe is small, the resistance to flow in the pipe is high This models less current For any constant voltage, increasing resistance will decrease current. We call this an inverse relationship

64 Factors that affect the resistance of a wire include… 1) Length:As length increases, resistance increases 2) Diameter: -As diameter increases, resistance decreases 3) Temperature: - As temperature increases, resistance increases 4) Material: -A wire that is a better conductor would have less resistance

65 Controlling the Flow Resistors – limit the amount of current Resistance – a measure of the difficulty electrons have passing through a resistor [Units = ohms (Ω) ]

66 Controlling the Flow Solutions can provide resistance to electric current – depends upon the amount of charged particles they contain Make sure that the solution is ionic Low resistance = high conductivity High resistance = low conductivity

67 Polygraph Lie detector – measures skin resistance, bp and respiration rate. Sweat is a salt solution thus is a conductor Resistance of the skin will be less since more sweat (contains salts which are ionic) is produced under stress

68 Variable Resistors or Rheostats SwitchesControlling the Flow Variable Resistors or Rheostats Switches control the flow by “breaking “ the circuit

69 Controlling the Flow Rheostat – a variable resistorTurning the rheostat dial changes how much of the resistor the current must flow through As the resistance is increased, less current flows As the resistance is decreased, more current flows

70 Your Task Check & Reflect # p 303

71 Georg Simon Ohm Found a relationship between potential difference, current and resistance (Ohm’s Law) MATH V = I x R

72 Ohm’s Law Written mathematically is:V= I x R Where: V = voltage (potential difference) (V) I = current (A) R = resistance (Ω) [rearranging equations]

73 Ohm’s Law Example What is the resistance of a light bulb if the batteries supply 3.0V and the current that runs through it is 0.4A?

74 Example Problems: A nine volt battery supplies power to a cordless curling iron with a resistance of 18 ohms. How much current is flowing through the curling iron?

75 Example A CD player with a resistance of 40 ohms has a current of 0.1 amps flowing through it. Sketch the circuit diagram and calculate how many volts supply the CD player? [V = 4 V]

76 Practice Ohm’s Law practice: p 307 “Skill Practice” # 1 – 3[click for - interactive circuit] Answers: A V Ω

77 Measuring ElectricityCheck & Reflect p #

78 Circuit Diagrams (aka schematic) Schematics have four basic parts:Electrical Circuits Circuit Diagrams (aka schematic) Schematics have four basic parts: Source: where electrical energy comes from Conductor: wire through which the current flows Control/Switch: device that can turn the device on or off Load(s): items along the circuit that convert electricity into other forms Note: symbols pg 312 & p 509

79 Circuits can be: Closed:-Charges (electrons) can flow without interruption 2) Open: - The electron flow has been interrupted by a break in the circuit -The circuit is not complete

80 Steps to Drawing a CircuitDraw with a pencil and ruler on graph paper or unlined paper Place components in a square or rectangular arrangement Make conductors straight lines with square corners Arrange diagram so conductors do not cross

81 Types of Circuits Series All charges move through the same pathwayCurrent passes through each load in order If load is interrupted circuit is broken

82 Types of Circuits Parallel Separate current path for each loadResistance decreases as loads are added (more paths added) Advantage: Can turn off one branch of the circuit without affecting the other branches

83 Practice Problems 1) Draw a circuit with a 2-cell battery and a light bulb. 2) Draw a circuit with a 4 – cell battery, 2 light bulbs, and an open switch that runs the light bulb 3) Draw a circuit with a 1.5 V cell, light bulb, and a closed switch that only runs a motor 4) Draw a circuit consisting of a four cell battery connected to two lamps in parallel (each controlled by separate switches) to an ammeter

84 End of Section PracticeRead p Check & Reflect # 1 – 9 & 11 p 316 Section Review # 1 – 5, 7, 8, & 9 p 317 Circuit Diagram Worksheets

85 Question 1 Draw a circuit with a 1.5 V cell, light bulb, and a closed switch that only runs a motor

86 Question 2 Draw a circuit consisting of a four cell battery connected to two lamps in parallel (each controlled by separate switches) and an ammeter

87 Question 3 Draw a diagram of a series circuit that has a four-cell battery, five bulbs and a motor. Add a resistor that impacts two bulbs and the motor.

88 Question 4 Draw a diagram of a parallel circuit that has a two-cell battery, two bulbs and a motor. Add a switch or switches that allow you to turn off all three items at once. The switch or switches must also allow you to turn the motor off while the light bulbs remain on. Be sure to indicate the current flow

89 Question 5 Draw a parallel circuit with a 1.7V cell powering 2 light bulbs and a motor. Include a switch(es) that can turn off 1 light and the motor but leave the rest of the circuit running. As well as a voltmeter.

90 Question 6 Draw a series circuit with a battery, four light bulbs, a resistor and a switch that controls the whole circuit.

91 Question 7 Draw a parallel circuit with a motor, resistor, one light bulb, and a switch that controls one of the loads. All powered by a 6V battery.

92 Question 8 Draw a schematic parallel circuit with a 3 cell battery hooked up to 5 lights, 1 motor and a resistor. With an open switch controlling three of the lights only. And an ammeter.

93 Electrical Devices Energy is ‘the ability to do work’

94 2) Electrical - energy of charged particles, transferred when they The four most common forms of energy are: 1) Chemical - potential or stored energy stored in chemicals, released when the chemicals react. 2) Electrical - energy of charged particles, transferred when they travel from place to place.

95 3) Mechanical - energy possessed by an object because of its motion or its potential to move.Thermal - kinetic energy of a substance

96 Energy can be converted to various forms of energyBatteries convert chemical energy into electrical energy Generators convert mechanical energy into electrical energy Electric motors convert electrical energy into mechanical energy

97 Chemical energy is the energy found in chemicals, including food.Glucose molecules are used in your body cells to produce thermal energy and mechanical energy.

98 Chemical energy can also be transformed into mechanical Chemical energy can also be converted into mechanical and sound energy (a CD player). Chemical energy can also be transformed into mechanical energy, with heat and light (dynamite).

99 Electric energy can be converted into moving energyElectricity and Motion Electric energy can be converted into moving energy Examples: remote control cars, electric motors Motion can also be converted into Electrical Energy Most electricity comes from the conversion of mechanical energy into electrical energy

100 Electricity and Light Electric energy can be converted intolight energy Example: Incandescent light bulbs Has a filament of highly resistant metal (tungsten) which glows brightly when current passes through it.

101 Electric Motors – convert electricity flowing through an electric field into mechanical energy.

102 Electric Motor Basic Parts: Armature: rotating shaft with the coilwrapped around it. 2) Brushes: usually bars of carbon pushed against the metal commutator springs. Make electrical contact with the moving commutator 3) Commuter: split ring that breaks the flow of electricity and then reverses the connection of the coil 4) Magnet

103 Direct and Alternative CurrentAC/DC: Alternating Current – flows forward then backward (60 Hz) Direct Current – flows in one direction

104 Transformers AC transformers Change voltageCan step-up( increases voltage) or step-down (decreases voltage) Read page 329

105 Motors vs. Generators A motor converts electrical energy into mechanical energy A generator converts mechanical energy into electrical energy

106 Your Task Check & Reflect p 331 # 1-8

107 Quiz What are the parts of a motor, in alphabetical order?What is the function of the commutator Motors convert energy into energy. Generators convert energy into energy What are the 4 types of energy Compare Parallel and Series Circuits

108 Measuring Energy Power P = E/t or P = I VRate at which energy is used measured in Watts (W) P = E/t or P = I V Sample Problems p 332 & 333 Time has to be in seconds

109 Power Example A hair dryer has a power rating of 1000W. It is plugged into a 120-V outlet. What is the current flowing through the hair dryer?

110 Power Example 2 A curling iron is plugged into a 110-V outlet. It uses A of current. What is the power rating of the iron?

111 Power is also defined as the energy per unit timeDescribes the amount of electrical energy converted to light, heat, sound and other forms Power= energy ÷ time P = E ÷ t 1 Watt = 1 Joule / 1 second

112 Example A microwave oven has a power rating of 800 W. If you cook a roast in this oven for 30 minutes at high, how many joules of electrical energy are converted to heat by the microwave?

113 Example What is the wattage of a frying pan that uses 300,000 joules of energy to cook bacon for ten minutes?

114 Inefficiency of Energy TransformationLaw of Conservation of Energy – energy cannot be created or destroyed only converted to other forms Input E is always greater than output energy Energy is most commonly lost as: Heat Sound Light

115 Efficiency Efficiency refers to the ratio of the useful energy output to the total energy input Energy efficiency saves money and reduces environmental harm % Eff = useful output E x 100% input E OR

116 Efficiency Example An incandescent light bulb uses 780 J of energy to produce 31 J of light. What is the efficiency of the light bulb?

117 Efficiency Example Calculate the efficiency of an 1000W kettle that takes 4 min to boil water. To heat the water to boiling point, it takes 196,000 J of energy. What is the efficiency of the kettle? Skill Practice p 336 C&R p 338 # 4,6 - 9

118 Energy Wasted by DevicesEnergy costs money Using less energy and reducing waste helps save money and is ecologically responsible.

119 Energuide Provide useful comparative information when shopping for appliances

120 Energy “Loss” Thermal energy is the most common form of energy loss – wasted energy Results from friction which is expelled by exhaust gases and to cooling systems

121 Reducing Friction Lubricants and well designed bearings can increase the efficiency of a motor. Section Review p 343 # 1 - 8

122 Quiz Time!!!!!

123 1) jolt kills 2) Draw an electrochemical cell. Label all parts 3) The positive electrode is called the and the negative electrode is called the 4) Explain electroplating 5) Draw a diagram explaining how protons and electrons interact in an insulator and in a conductor 6) A variable resistor is also known as a 7) A 12V battery supplies power to 3 light bulbs and a motor in parallel, with a resistor with a rating of 18 ohms. Draw a schematic for this as well as calculate how much current is flowing through the circuit.

124 Electrical Energy & Societyp

125 Sources & AlternativesElectrical energy can be generated using a turbine and a generator Various methods can be used to turn turbines: steam wind tides…

126 Sources & AlternativesTurbines can be turned directly by mechanical energy or indirectly by converting the energy source to heat which then converts water to steam which turns the turbine.

127 Steam Generation (Nuclear, fossil fuel, biomass, geothermal …)Any fuel that can boil water can be used to provide the mechanical energy of steam to turn a electrical turbine. (Nuclear, fossil fuel, biomass, geothermal …) [see Fig 4.1]

128 Fossil Fuels: Include coal, oil and natural gas. Sources of Energy Fossil Fuels: Include coal, oil and natural gas. They provide heat energy necessary to change water into steam which then turns a turbine. The turbine shaft rotates to produce electricity. These fossil fuels are non-renewable Coal and natural gas generated power contributes to air pollution Byproducts of Burning Fossil Fuels High carbon dioxide emissions contribute to global warming while sulfur dioxide emissions produce acid rain.

129 Hydroelectric: electricity is generated in areas where large volumes of water are collected behind dams. The collected water has high potential energy (gravitational energy), which when released spins the turbine and generator to produce electricity The initial cost of constructing a hydroelectric power plant is high but once in operation the cost of producing electricity is lower Water is a renewable resource

130 Wind Generators: this energy is harnessed by large propeller-type blades, which turn a shaft - connected to a generator. Renewable resource

131 Nuclear Steam GenerationNuclear reactors use uranium to produce heat energy Chernobyl

132 Geothermal: molten rock beneath Earth’s surface heats the ground water creating steam which is transported through pipes to drive turbines Except for the sulfur smell, geothermal energy does not pollute the environment Iceland has been geothermal energy for years

133 Biomass: refers to organic materials present in garbageOrganic materials decompose to produce methane gas which is collected and used as fuel You can also burn it.

134 Solar Power: Solar cells (made from silicon) enable the energy from the sun to be transformed (photoelectric effect) into electricity. The initial cost is high but the energy produced is inexpensive and pollution free

135 Renewable energy sources include:Alternate Sources Renewable energy sources include: Tides Wind Solar Batteries (chemical) Biomass

136 Electricity and the EnvironmentStrip mining techniques removes all plants and animals from large areas of land resulting in habitat and species destruction. Oil and Gas wells can often give off poisonous gases. Steam turbines often release warm water into nearby lakes and rivers. The increase in water temperature can affect the local marine ecology and can kill fish. Mines and refineries that produce nuclear fuel can also cause damage to the environment, because of the radioactive waste. Dams, wind farms and solar cell arrays can decimate large areas of ecological habitat. Tidal power plants can disrupt the habitat of fish and other marine life.

137 Your Task Check and Reflect p 350 # 1-3, 6-8 & 10

138 4.2 Environmental Concerns p 351 - 353Read 351 – 353 Check & Reflect p 353 # 4, 8, 9

139 4.3 Technology & Society p 354 - 359Read p 354 – 358 Check & Reflect p 358 # 1 – 4 Section Review p 359 # 2, 5, 7 & 9

140 End of Unit Read Unit Summary p 360Read Three Gorges Dam p 361 (no research reqd.) Unit Review p 363 – 365 1 (define), 4,5,7,9,10,12, ,18- 20,25,29