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 What is “green energy”?  What is a “carbon footprint”?  Why should you care?  How can you reduce your carbon footprint? p142.

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Presentation on theme: " What is “green energy”?  What is a “carbon footprint”?  Why should you care?  How can you reduce your carbon footprint? p142."— Presentation transcript:

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3  What is “green energy”?  What is a “carbon footprint”?  Why should you care?  How can you reduce your carbon footprint? p142

4  What do you see in the cartoon?  Turn and tell your partner 2 things  Share out  Record in your notebook p142

5  Record in your notebook  Usually, when you need electricity, all you have to do is plug an appliance into the wall  How is the electricity that you use generated?  Make a list of energy sources  Compare with a partner p142

6 1.) Where does electricity come from? How does it get to your house?  All Sacramento county households get their electricity from SMUD (Sacramento Metropolitan Utility District) and natural gas from PG&E (Pacific Gas and Electricity)  https://www.smud.org/en/about-smud/company- information/power-sources.htm https://www.smud.org/en/about-smud/company- information/power-sources.htm  Ask for a copy of your most recent SMUD bill. Make a copy and bring it to class. p143

7 Basic (world)Basic (USA)Dream house Compare with a partner p143

8 Highest energy user: Air conditioning/heaterHot water heater Clothes dryerRefrigerator freezer Medium energy users: Tv/computersMicrowave DishwasherHair dryer Toaster/oven Low energy users: FansLights Stereo/boom boxcoffee maker

9  Using only the items in the bag, make the light bulb glow.  Draw a picture in your notebook  Explain what you think is happening p144

10 1. Electricity is created when electrons move from one place to another. Electricity can also be created when work is done to move a magnet within a coil of wire (generator) 2. Electrons move to places with less negative charge (opposite charges attract, similar charges repel) 3. Energy can be transferred from one type to another. 4. Power companies (like SMUD) get electricity from different sources (hydro, gas, solar, wind, geothermal) 5. For an electric current to exist in a circuit, the circuit must form a closed loop. Switches are used to open/close a circuit. Metals conduct easily. Other materials do not and act as insulators. 6. A fuse burns out if the current becomes too large 7. As the energy output of a circuit increases, the energy needed also increases p145

11  Equipment in the box on the lab bench  Hand generators can break (and cost $$)  Crank them slowly and gently  Get your notebook stamped when you are finished and put everything back in the box.  Answer CU (p601) 1-3 PtoGo (p604) 1-9 Get your notebook stamped again P144

12  What do you see in the picture? Turn and share 2 things that you see with your neighbor  What do you think? What is electricity and how does it move through a circuit? Record your ideas in your notebook…  Share out P146

13  Volunteer to be the battery:  Volunteer to be the light bulb (how do we know when the bulb is “on”?)  Everyone else is an electric charge (electron)in the circuit  Arrange yourselves into a complete circuit  Round 1

14 ROUND 1 (RECORD IN YOUR NOTEBOOK)ROUND 2: ADD VOCALS  The battery (source of beads) gave each unit of charge (student electron) a certain amount of energy (one bead).The charge then gave that energy to the light bulb (dancing student) who converted the energy into light, The charges (student electrons) continue back to the battery to get more energy and repeat the process.  1 volt battery means…  1 amp means…  The battery announces “the battery voltage is 1 volt which equals one joule of energy for each coulomb of charge”  Any student receiving a block responds “one coulomb of charge receiving one joule of energy”  Teacher says “please move along, one coulomb per second is one ampere (amp) of current”  The light bulb says “I just received one joule of energy from that coulomb of charge” p146

15  Round 3  Voltage=3 volts means… (battery gives each charge 3 joules of energy)  Current=1 amp means… ( coulomb of charge moves by every second)  Record what happens  Round 4  Voltage=1volt means…  Current=2 amps means…  Record what happens p146

16 a.) there is a 5 volt battery b.) current is 3 amps c.) there is a two volt battery d.) the current is increased to 5 amps e.) the two-volt battery is replaced with a four-volt battery f.) the current increases from 2 amps to 3 amps p147

17  Now we need 2 light bulbs. 1a.) Describe what will happen if we put 2 bulbs in our circuit, one right after the other.  In order to have any light in the second bulb, an electron (student) must keep some of the energy from the first bulb (so less energy goes to the first bulb) to give to the second. This is called resistance. How much energy goes to the first bulb depends on the bulb. For now, half of the energy will go to the first bulb, and half to the second bulb. p147

18  2a.) Since the brightness of a bulb depends on how much energy is used up in the bulb during a given time, how would the brightness of each of the 2 bulbs in the series circuit compare with the brightness of a single bulb hooked up to the same battery?  3 A) 4 light bulbs in series result in…  B) two light bulbs and a 3-volt battery  C) two light bulbs, but twice as much current  D) two different kinds of light bulbs in series  Get a stamp P147-8

19 Get a stamp  CU (p610) 1-4 Get a stamp  PtoGo (p ) 1-4 Get a stamp 1 Bulb2 BulbsWhich is brighter? voltagecurrentvoltagecurrent 1111One bulb

20 8. Electrical power is the speed that energy is transferred. Power is measured in Watts (W) 9. Electric potential or voltage is the potential energy per unit of charge, and is measured in volts 1 volt=1 joule/charge 10. Current is the amount of charge per unit of time that flows past a point and is measured in amperes (amps) 1amp=1 charge/second 11. Resistors are electronic devices (like light bulbs) that resist the flow of electric charge 12. In a series circuit there is one path for current to follow. The sum of the voltage dropped at each resistor is equal to the total voltage supplied to the circuit (2 light bulbs in series: each gets ½ the voltage and are therefore ½ the brightness) p145

21  What do you see in the picture? Turn and share 2 things that you see with your neighbor  What do you think? When one light bulb in your house goes out, can the other light bulbs remain on? Can a circuit be set up to allow this? Record your ideas in your notebook…  Share out p149

22  Back to our electron shuffle model…  Round 1: Set up a series circuit. What happens again when we put a second bulb into this series circuit? Draw a picture of this circuit.  Round 2: Now we are going to make a parallel circuit. At a certain point, a junction, electrons will have to choose which light bulb to give their energy to. Draw a picture of this circuit. p149

23  The battery announces “the battery voltage is 1 volt which equals one joule of energy for each coulomb of charge”  Any student receiving a bead responds “one coulomb of charge receiving one joule of energy”  Teacher says “please move along, one coulomb per second is one ampere (amp) of current”  The light bulb says “I just received one joule of energy from that coulomb of charge” Record in your notebook:  1 volt battery means… (battery gives each charge 1 joules of energy)  1 amp means… (1 coulombs of charge move by every second) 3.)Record what happens: The battery: The electrons: The light bulbs: p149

24 Each light bulb receives one joule (bead) for each coulomb of charge (from each student electron) that passes through the light bulb. p149

25 (1)(1)/2=  Because the current divides equally among the light bulbs, each light bulb receives an equal share of the coulomb of charge. 2 bulbs means each bulb gets one half.

26  The battery announces “the battery voltage is 1 volt which equals one joule of energy for each coulomb of charge”  Any student receiving a block responds “one coulomb of charge receiving one joule of energy”  Teacher says “please move along, one coulomb per second is one ampere (amp) of current”  The light bulb says “I just received one joule of energy from that coulomb of charge” Record in your notebook: Draw a picture of this circuit p150

27  Each light bulb receives one joule (bead) for each coulomb of charge (from each student electron) that passes through the light bulb. (same amount as the last round)

28  Three bulbs means each bulb gets 1/3 per second (different amount of current than the last round)

29 Round 4  Voltage=3 volts (battery gives each charge 3 joules of energy)  Current=1 amp (1 coulombs of charge move by every second) Round 5  Voltage=1 volt (means…)  Current=2 amps (means…) p150

30 7a.) 4 bulbs in a parallel circuit (the current passing by each light bulb would be…) (1)(1)/4= One fourth (1/4) coulomb per second or one student passing by every 4 seconds p150

31 7b.) three light bulbs and a 3 volt battery (3)(1)/3= Three times the charge means three times as bright Each light bulb receives 1/3 of a coulomb of charge per second=1 ampere p150

32 7c.) 3 light bulbs and larger current (2 amps) (1)(2)/3= Each light bulb would still get the same amount of energy per charge (student) passing by, and 1/3 the larger current, but there is twice as much current, so each bulb would get 2/3 amps each p150

33 7d.) 4 light bulbs and 6 volts (6)(1)/4 = Each light bulb would receive six joules of energy for every coulomb (student) that passes and each light bulb would receive ¼ the current of 1 amp (one student would pass by every 4 seconds) p150

34 7e.) 3 bulbs that are not identical Each would get the same amount of energy per charge (student), but different amounts of charge because they are not identical (the number of students passing by per second would vary) p150

35  Use Phet: Circuit Construction Kit (DC only)Phet: Circuit Construction Kit (DC only)  Follow directions and answer questions on the handout (Some properties of electric circuits)  Get a stamp when finished  CU (p618) 1-4  PtoGo (p ) 1-9  Get stamps when finished P150 P151

36 PART VI ResistanceCurrent0.60Voltage a) What is the relationship between resistance and current? b) What is the relationship between resistance and voltage? c) Explain PHET: Some Properties of Electric Circuits

37 13. In a series circuit current flows along one path. In a parallel circuit the current flows along parallel paths. 14. The voltage drop across each branch is equal the total voltage 15. The sum of the current in each branch equals the total current p145

38  What do you see in the picture? Turn and share 2 things that you see with your neighbor  What do you think? What determines the brightness of a bulb? What determines how much current flows in a circuit? Record your ideas in your notebook…  Share out p151

39  Today you will use the phet simulation: Circuit Construction Kit (in place of the lab in the text book)  All parts should be completed today (before our next class meeting)  CU (p626)  PtoGo (p ) 1-4  CDP p152

40 16. Voltmeters are used to measure voltage (which is measured in volts or V) 17. Ammeters are used to measure current (which is measured in amps or I) 18. Resistance is directly proportional to the voltage dropped and inversely proportional to the current 19. Resistance is measured in ohms or Ω 20. Ohm’s Law: voltage=(current)(resistance) V=IR and I=V/R and R=V/I p145

41 6. Your hair dryer has a resistance of 9.6 ohms and you plug it into the bathroom outlet. Assume household voltage to be 120 volts, and that different parts of your house are connected in parallel. a.) What current will it draw? I=V/R=120V/9.6=12.5 amps b.)Suppose that your brother has an identical hair dryer and plugs it into a parallel part of the circuit. What current will the two hair dryers draw? Parallel circuits have the same voltage drop and the same current…12.5 amps amps=25 amps total c.) If the maximum current the circuit breaker in the system can handle is 20 amps, what do you think will happen? The circuit breaker will “break” when the current exceeds 20 amps p153

42 8.) A 12 volt battery is hooked up to a 3 ohm resistor. The current through the resistor is I=V/R=12/3=4 amps p153

43 9.) A 2 ohm resistor has 4 amps of current running through it. The voltage drop (or potential drop) across the resistor is V=IR=(4)(2)=8 volts p153

44  What do you SEE in the cartoon?  Use what you see, and your prior experience to answer the questions What Do You Think in your notebook  What do you think is the function of a fuse or circuit breaker?  Exactly what conditions do you think make a fuse blow or a circuit breaker trip? p154

45 1.) Watch the following demonstrations on youtube  Balloon fuse pU pU  Electricity review w&feature=related w&feature=related 1a.) what happens to the light in the video when the fuse blows? p154

46 2a.) Why do you think that the fuse blew? b.) Why did the circuit require multiple appliances to blow out the fuse? c.) Explain why the fuse behaves the way it does. p154

47 ApplianceVoltagePower (Watts)Current (Amps) Hot plate Lamp with 100 Watt bulb heater ) Copy the table into your notebook. 5.) Calculate the current for each appliance I=P/V 6.) Find the total current and total power used above. The current rating on the power strip was 10 A. Did the total current of the appliances exceed that rating? CU (p638) 1-4 PtoGo (p ) 1-13 CDP p155

48 20. Power is the rate at which energy is delivered to an object or a load in a circuit. Power is measured in watts. One Watt is one joule of energy supplied in one second of time (1 W= 1 J/s). For a circuit, the power can be calculated by multiplying current and voltage (P=IV) 21. When the flow of electric charge, or current, occurs easily in a material it is called a good electric conductor. When the material does not allow charge to flow easily (or not at all) it is called an insulator. 22. Fuses and circuit breakers are used as safeguards to protect the circuit from too much current and prevent electrical fires from starting. A fuse consists of a wire that will melt when too much current flows through it, thus opening the circuit. A fuse must be replaced when blown (to make a closed circuit). A circuit breaker is a switch that opens when too much current flows through it. A circuit breaker must be reset when tripped for current to resume flowing. 23. The power (and current) drawn by a circuit depends upon the voltage of the circuit and the resistance of the circuit. Decreasing the resistance of a circuit increases the power (and current) for a fixed voltage. p157

49  What do you see? Many electrical switches are operated manually (by hand), and many others are automatic, turning appliances on and off in response to a variety of conditions.  List at least 3 different kinds of automatic switching devices in the picture.  What are the conditions that cause the on/off action of the switch? p158

50  Today you will use the phet simulation: Circuit Construction Kit (in place of the lab in the text book)  All parts should be completed today (before our next class meeting)  CU (p654) 1-3  PtoGo (p ) 1-13  CDP p158

51 24. Switches are used to control the total circuit or part of a circuit. 25. Energy and charge are conserved in a circuit. Using these principles and Ohm’s Law results in the following relationships for series and parallel circuits: Series:Parallel: V total = V 1 + V 2 + V 3 etc.V total = V 1 = V 2 = V 3 etc. I total = I 1 =I 2 =I 3 etc.Itotal = I 1 + I 2 + I 3 etc. R total = R 1 + R 2 + R 3 etc.1/R total = 1/R 1 + 1/R 2 + 1/R 3 etc. 26. For any junction in a circuit, the current flowing into the junction must equal the current leaving the junction. 27. The energy consumed in the parts of a circuit is equal to the the energy supplied by the power source 28. Adding resistance in parallel decreases the circuit resistance and increases the circuit current and power. p157

52  What is an electromagnet? How does it work?  Draw and label the parts of an electromagnet  What is a simple test to tell if an electromagnet is working?  Video 1:  Video2:  Video 3: p154

53  Use the PHET simulation Magnets and electromagnets s-and-electromagnets Get a stamp when you get to the bottom of each page P154-5

54 1. The direction of a magnetic field outside a magnet is from north to south (that is why a compass points north) 2. The earth’s magnetic field is caused by currents in the earth’s core and changes over time. 3. All magnetic fields are produced by moving electric charges (electromagnets use electricity). The field is perpendicular to the wire. Changing the magnetic field changes both the current and the voltage. 4. A moving charge is deflected when it crosses magnetic field lines. This force can be used to do work. The magnetic field is strongest near the center 5. A generator converts energy into electricity. A motor turns electricity into mechanical energy. 6. Faradays law p155

55  NOVA: Magnetic Storm video (youtube) wkstyoutube  CDP 36-1  Phet: Magnetism and Electromagnets  Last chance for stamps on these wksts!

56 p156

57  Summary Get a stamp at the end of class p159

58  When I hit the table with the hammer, where does the energy come from? Where does it go?  When I hit 2 metal spheres together, where does the energy come from? Where does it go? p160

59  Hot water Observations: Explanation:  Cold water  Observations: P160

60  What is temperature a measure of?  How does a thermometer work?  What temperature scales do you know?  What is absolute zero? p161

61  Explain how the two cups of water are different p162

62 1. Measures the movement (speed) of molecules (more energy=more speed) 2. As the molecule speed increases, the molecules spread out taking up more space. This is what happens in a thermometer. 3. Centigrade (celsius), kelvin, farhenheit 4. Absolute zero is when molecules stop moving and therefore take up zero space (impossible!) p163

63  What do you SEE in the cartoon?  Use what you see, and your prior experience to answer the questions What Do You Think in your notebook  As you add cold milk to hot coffee, you expect that the milk will get warmer, and the coffee will get a bit colder. What determines the final temperature of the coffee and the milk? p164

64  What happens if you mix 50ml of water at 50 o C and 50ml of water at 100 o C?  Explain:  Try it! Heat Mixes Lab (part 1)  Steps 1-4 equal amounts of hot/cold  Steps 5-7 2/3 hot:1/3 cold  Steps 8-9 1/3 hot:2/3 cold  Heat Mixes Lab (part 2)  Steps 1-6 equal amounts hot nails: cold water  Steps 7-11 equal amounts cold nails: hot water  Was your prediction correct? P164

65  Steps 1-4 equal amounts of hot/cold Hot 53.5C: cold 3.4C final 29C  Steps 5-7 2/3 hot:1/3 cold Hot 45.5C: cold 4.0C final 29C  Steps 8-9 1/3 hot:2/3 cold Hot 48.3C: cold 4.5C final 19.9C Heat Mixes Lab (part 2)  Steps 1-6 equal amounts hot nails: cold water Hot 37.7C: cold 21.1C final 22.8C  Steps 7-11 equal amounts cold nails: hot water Hot 48.2C: cold 3.7 final 43.5C

66 1. Describe at least two ways that students made predictions. The evidence supported which method? 2. Equal amounts of hot water (80 o C) are added to cold water (10 o C). Explain how to predict the final temperature (and then do the math!) 3. Students performed the experiment, but only measured a final temp of 40 o C Where did the extra heat go? 4. Predict the final temp of 3 parts 30 o C and 1 part 70 o C water. 5. Did adding equal amounts of metal nails have the same effect as adding equal amounts of water? What does this say about heating metal compared to heating water? Get a stamp when finished P165

67  Follow the directions on the handout.  Answer all the questions and make the graph in your notebook using a graph stamp.  Get your notebook stamped when you are finished.  CU (p672) 1-4  CDP 21-1 p165

68 5. Temperature is a measure of the average kinetic energy of the particles that make up the object. 6. The specific heat of a material is a measure of how much energy is required to heat 1 gram of material 1 degree celcius. 7. Two objects in contact will reach the same temperature (equilibrium) 8. 1 st Law of thermodynamics: heat = energy + work 9. 2 nd Law: Heat is a form of energy and can be transformed from a warmer object to a cooler object. Heat always flows from warmer to colder 10. entropy = disorder when heat flows from warmer to colder entropy (disorder) increases p163

69 11. A conductor allows heat to flow easily. An insulator traps heat and does not allow it to flow. 12. Heat energy (Q) is measured by multiplying the mass (in grams) times the temperature change times a specific heat constant (the constant for water is 1 g/C/cal or 4.17 g/C/Joule) Q=m(T f -T i )c p163

70 Hot nails 37.7C: cold water 21.1C final 22.8C  How much heat was lost by the nails? Q=m(T f -T i )c mass nails =41g c steel =0.12 g/C/cal  Where did that heat go?  How much heat was gained by the water? Q=m(T f -T i )c mass water =41g c water =1.00 g/C/cal p168

71  Energy is transferred by direct contact  Give an example: p168

72  Energy is transferred by the mass motion of molecules  Give an example: p168

73  Energy is transferred by electromagnetic radiation  Give an example: p168

74 The Drinking Bird Lab  So what makes the bird drink?  Video Video  Video explanation Video explanation  What NOT to do! What NOT to do!  Answer all the questions Get a stamp when you finish p169

75  Using only your hands, find the coldest substance around you…  How can we remove enough heat to make ice cream?  Video Video  Follow the directions or your ice cream will not turn out! Get a stamp when you are cleaned up.  Answer all the questions and get another stamp. p171

76  Draw 6 water molecules in each box (remember molecules are always the same size, only the spacing is different  Make a statement about the density of water molecules in each phase solidliquidgas Does it take energy to melt ice? p169

77  Make a line graph to show the temperature vs the heat energy of water. Include these words: solid ice, liquid, water vapor(steam), melting, freezing, boiling, condensing T E M P E R A T U R E HEAT ENERGY

78 Finish CDP p169

79 PhaseHeat constant per gram water Ice (solid) Melting ice to liquid 80 cal/gram (Liquid) water 1 cal/gram /degree 4.18 joules/g/ degree Boiling/evap540 cal/gram Steam (gas) 1.) How much heat is required to melt 5 grams of ice? 2.) How much heat is required to heat 45 g of ice water to 60C? 3.) How much heat is required by your stomach melt 15 grams of ice and raise the water temperature to 40C? p170 Does the water change temperature? If yes….Q=mc If no…..Q=mΔTc

80 1.) How much heat is required to melt 5 grams of ice? (5 grams)(80 cal/gram) = 400 Cal 2.) How much heat is required to heat 45 g of water? (45 grams)(60)(1 cal/gram/degree) = 2700 cal 3.) How much heat is required by your stomach melt 15 grams of ice and raise the water temperature to 40C? (15)(80) = 1200 cal (15)(1)(40) = 600 cal total = 1800 calories

81  What do you SEE in the cartoon?  Use what you see, and your prior experience to answer the questions What Do You Think in your notebook  What do we use hot water for?  Most American homes use more energy to heat water than all the other energy uses combined. There are 2 main types of water heaters. A big tank of water that is heated by a gas flame (and kept hot until you want to use it) and “instant” water heaters that use electricity through an immersion unit to heat water only when you want to use it.  Which type do you have at home?  Which do you think is more efficient? p173

82  Assemble a calorimeter using two styrofoam cups on the base and another as a lid (making holes in the lid for the thermometer and the immersion heater. Follow the directions in the book (p )  Make the water at least 25 degrees hotter before you stop  Answer all the questions and calculations in your notebook  Get your notebook stamped when you are finished. p173

83 13. Efficiency of a system = useful energy output/total energy supplied 14. Electrical energy E = Pt = VIt 15. Electrical energy is measured in kilowatt- hours st Law of Thermodynamics. Energy is conserved. Energy can be transferred, but is neither created or destroyed p163

84  How much energy do you use?  Follow the directions on the handout. Do all work in your notebook. The SMUD handouts stay in this room!  Get a stamp when finished  CU p682) 1-4 Get stamped when finished (you do not have to do the PtoGo questions on the back…you already did them!) P174-5

85  Rank the 3 appliances from most efficient to least efficient.  Rank the 3 appliances from greatest cost to heat 1 beaker of water to least cost.  If high-efficiency appliances cost more, are they worth the extra cost? p176 Heat Coil Hot Plate Microwave

86 Heat coilHot platemicrowave Mass of water250 grams Cold water temp21.9 o C22.7 o C22.3 o C Appliance power250 watts690 watts650 watts Heating time113 sec2 min1 min 11 sec Final water temp45.4 o C51.4 o C65.1 o C 2.) Do you want to change any of your predictions? Give a reason! 3.) Calculate the heat energy for each beaker of water. 4.) Calculate the energy given off by each appliance. 5.) Calculate the efficiency of each appliance. 6.) Which appliance was most efficient? 7.) Assume energy costs $10.40 cents per watt-s and calculate the cost for each appliance to heat the same beaker of water. Does this surprise you? p176

87  Follow the directions in the book (p )  Answer all the questions and do the calculations in your notebook.  Get your notebook stamped when you are finished.  CU (p695) 1-6  PtoGo (p698) 1-9 P176-7

88 17. Heat may be transferred by conduction, convection, or radiation. Conduction occurs when two objects are touching each other. Convection occurs through the movement of a fluid. Radiation occurs when the warmer object emits electromagnetic waves in all directions and the cooler object absorbs some or all of it nd Law of Thermodynamics. Heat flows from hot to cold, increasing the disorder by making molecules move faster (entropy) rd Law of Thermodynamics. We can never reach absolute zero because it is impossible for molecules to stop moving. p163

89  Study your quizzes (Electricity and Heat)  Study your purple model sheets  Practice by playing jeopardy (on my website)

90

91  Build a scale model house  Compare energy costs and present on a poster  Wire your house with simple circuits and light bulbs


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