Ch 6 Electricity for everyone

Green Energy and Home Design

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

Investigation #1 (p598) p142 What do you see in the cartoon? Turn and tell your partner 2 things Share out Record in your notebook

What do you Think? (p598) p142 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

Part A p143 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 Ask for a copy of your most recent SMUD bill. Make a copy and bring it to class.

List what appliances are needed in your house: Basic (world) Basic (USA) Dream house Compare with a partner

Appliances by energy use Highest energy user: Air conditioning/heater Hot water heater Clothes dryer Refrigerator freezer Medium energy users: Tv/computers Microwave Dishwasher Hair dryer Toaster/oven Low energy users: Fans Lights Stereo/boom box coffee maker

How many physics students does it take to light a light bulb? Using only the items in the bag, make the light bulb glow. Draw a picture in your notebook Explain what you think is happening

Electricity model: Section 1 DQ: How does electricity work? p145 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

Part B (p599-600) Steps 1-3 only 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

Section 2 (p606-609) P146 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

Investigation 2: The Electron Shuffle Part A: Modeling a Simple Circuit 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

p146 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”

This is the ELECTRON SHUFFLE This is the ELECTRON SHUFFLE. What are the variables that we could change? p146 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

On your own p608 #9 Record how the electron shuffle would change under the following conditions: 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

Part B: Modeling a series circuit 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.

Part B (p608) P147-8 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

Draw and complete the chart for #4 (p609) 1 Bulb 2 Bulbs Which is brighter? voltage current 1 One bulb 2 4 3 Get a stamp CU (p610) 1-4 Get a stamp PtoGo (p612-613) 1-4 Get a stamp

Electricity model: Section 2 p145 Electricity model: Section 2 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)

Investigation 3 Series and Parallel Circuits (p614-617) 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

Investigation Part A; Modeling a parallel circuit 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.

Round 2 (2 bulbs in parallel): jan-jun go to bulb one jul-dec bulb two 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 4a.) The battery provided each coulomb of charge with one joule of energy. How much energy did each light bulb get from each coulomb of charge? Each light bulb receives one joule (bead) for each coulomb of charge (from each student electron) that passes through the light bulb.

4b.) The charges left the battery at the rate of one coulomb per second. What was the current through each light bulb? (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.

Round 3 (3 bulbs in parallel): jan-apr bulb one, may-aug bulb two, sep-dec bulb three 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

4c.) The battery provided each coulomb of charge with one joule of energy. How much energy did each light bulb get from each coulomb of charge? 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)

4d.) The charges left the battery at the rate of one coulomb per second. What was the current through each light bulb? (1)(1)/3= Three bulbs means each bulb gets 1/3 per second (different amount of current than the last round)

Continue recording in your notebook: p150 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 How does a parallel circuit change under these conditions? (1 volt and 1 amp) 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

7b.) three light bulbs and a 3 volt battery (3)(1)/3= p150 How does a parallel circuit change under these conditions? (3 volt and 1 amp) 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

7c.) 3 light bulbs and larger current (2 amps) (1)(2)/3= How does a parallel circuit change under these conditions? (1 volt and 2 amp) 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

7d.) 4 light bulbs and 6 volts (6)(1)/4 = How does a parallel circuit change under these conditions? (6 volt and 1 amp) p150 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)

7e.) 3 bulbs that are not identical How does a parallel circuit change under these conditions? (1 volt and 1 amp) p150 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)

Part B: Comparing series and parallel circuits Use 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 (p621-622) 1-9 Get stamps when finished P151

This is OHM’S Law: V=IR PHET: Some Properties of Electric Circuits Part VI Resistance Current0.60 Voltage 10 0.90 9.00 15 0.60 20 0.45 25 0.36 30 35 40 45 50 55 a) What is the relationship between resistance and current? b) What is the relationship between resistance and voltage? c) Explain This is OHM’S Law: V=IR

Electricity model: Section 3 p145 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

Section 4 (p623) p151 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

p152 investigation 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 (p629-630) 1-4 CDP 33-2 34-1

Electricity model: Section 4 p145 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

p153 PtoGo (p629) 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 + 12.5 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 PtoGo (p629) 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

PtoGo (p630) p153 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

Section 5 electric power: load limit (p631-643) 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?

Investigation 1.) Watch the following demonstrations on youtube p154 Investigation 1.) Watch the following demonstrations on youtube Balloon fuse http://www.youtube.com/watch?v=m3U4k_xTSpU Electricity review http://www.youtube.com/watch?v=l0nCSzqefnw&feature=related 1a.) what happens to the light in the video when the fuse blows?

Teacher demo: when you plug a hot plate, a lamp with a 100 watt bulb, and a heater into a power strip and turn them all on at the same time, the power strip will turn itself off. p154 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.

Below are the appliance ratings: Voltage Power (Watts) Current (Amps) Hot plate 120 800 Lamp with 100 Watt bulb 100 heater 300 4.) 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 (p641-642) 1-13 CDP 34-2 35-1

Electricity model: Section 5 p157 Electricity model: Section 5 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.

Section 6 CVR in Parallel and Series: Who’s in control? (p644-659) 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 Investigate 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 (p658-659) 1-13 CDP 35-2 35-3

Electricity model: Section 6 p157 Electricity model: Section 6 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: Vtotal = V1 + V2 + V3 etc. Vtotal = V1 = V2 = V3 etc. Itotal = I1 =I2 =I3 etc. Itotal = I1 + I2 + I3 etc. R total = R1 + R2 + R3 etc. 1/Rtotal = 1/R1 + 1/R2 + 1/R3 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.

How can electricity create a magnet? 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: http://www.youtube.com/watch?v=emlzh9XXWgQ Video2: http://www.youtube.com/watch?v=frYorKTKdeI Video 3: http://www.youtube.com/watch?v=_ygmHnjNYNo p154

Electromagnetism Use the PHET simulation Magnets and electromagnets http://phet.colorado.edu/en/simulation/magnets-and-electromagnets Get a stamp when you get to the bottom of each page

Magnetism model p155 The direction of a magnetic field outside a magnet is from north to south (that is why a compass points north) The earth’s magnetic field is caused by currents in the earth’s core and changes over time. 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. 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

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

Flower power 2 I R 2 IV V /R p156 P V I R

How Electrical Grids work webquest 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19-31 32-49 50-70 p159 Summary Get a stamp at the end of class

It’s always about energy! p160 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 Hot water Observations: Explanation: Cold water Observations: What will happen when you add 1 drop of food coloring to each beaker? Record your prediction and then gently add one drop to each beaker. P160 Hot water Observations: Explanation: Cold water Observations:

White board your group answers to share out: What is temperature a measure of? How does a thermometer work? What temperature scales do you know? What is absolute zero?

Draw a picture of 10 water molecules in a cup of cold water, and then the same 10 molecules of water in a warm cup of water (same size cup!) p162 Explain how the two cups of water are different

p163 Temperature model driving question: what does temperature really measure? 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!)

Section 7: Laws of Thermodynamics (p664-677) 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?

Mixologist P164 What happens if you mix 50ml of water at 50oC and 50ml of water at 100oC? 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?

Heat Mixes Lab (part 1) Hot 53.5C: cold 3.4C final 29C 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

Describe at least two ways that students made predictions Describe at least two ways that students made predictions. The evidence supported which method? Equal amounts of hot water (80oC) are added to cold water (10oC). Explain how to predict the final temperature (and then do the math!) Students performed the experiment, but only measured a final temp of 40oC Where did the extra heat go? Predict the final temp of 3 parts 30oC and 1 part 70oC water. 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

Investigation Follow the directions on the handout. p165 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

Energy Model: Section 7 DQ: what is enegy and how is it transferred? p163 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. 1st Law of thermodynamics: heat = energy + work 9. 2nd 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

Energy Model/PtoGo (p676-677) 1-9 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(Tf-Ti)c

Heat Mixes Lab (part 2) revisited Hot nails 37.7C: cold water 21.1C final 22.8C How much heat was lost by the nails? Q=m(Tf-Ti)c massnails=41g csteel=0.12 g/C/cal Where did that heat go? How much heat was gained by the water? Q=m(Tf-Ti)c masswater=41g cwater=1.00 g/C/cal

conduction p168 Energy is transferred by direct contact Give an example:

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

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

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

We all scream for ice cream! Using only your hands, find the coldest substance around you… How can we remove enough heat to make ice cream? 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

How much heat energy does it take? p169 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 solid liquid gas Does it take energy to melt ice?

Whiteboard time… 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 R A U HEAT ENERGY

Phase changes of water diagram (white book p459) Finish CDP 23-1 23-2

Solving problems Phase Heat 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/evap 540 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

Answers 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

Section 8: Energy Consumption (p678-680) 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?

Investigation (do all steps 1-5) 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 (p679-680) 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.

Energy Model: Section 8 p163 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 16. 1st Law of Thermodynamics. Energy is conserved. Energy can be transferred, but is neither created or destroyed

Energy Consumption (PtoGo p686) 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

Section 9: Comparing Energy Consumption (p691-698) Heat Coil Hot Plate Microwave 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 Which appliance is most efficient? 1.) Copy the chart into your notebook. Heat coil Hot plate microwave Mass of water 250 grams Cold water temp 21.9oC 22.7oC 22.3oC Appliance power 250 watts 690 watts 650 watts Heating time 113 sec 2 min 1 min 11 sec Final water temp 45.4oC 51.4oC 65.1oC 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?

investigation Follow the directions in the book (p691-693) 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

Energy model: Section 9 p163 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 18. 2nd Law of Thermodynamics. Heat flows from hot to cold, increasing the disorder by making molecules move faster (entropy). 19. 3rd Law of Thermodynamics. We can never reach absolute zero because it is impossible for molecules to stop moving.

Unit Test Friday! Study your quizzes (Electricity and Heat) Study your purple model sheets Practice by playing jeopardy (on my website)

Ch 6 Electricity For Everyone

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