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Ch 6 Electricity for everyone

Ch 6 Electricity for everyone. Green Energy and Home Design. p142. Whiteboard. What is “green energy”? What is a “carbon footprint”? Why should you care? How can you reduce your carbon footprint?. What do you see in the cartoon? Turn and tell your partner 2 things Share out

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Ch 6 Electricity for everyone

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  1. Ch 6 Electricity for everyone

  2. Green Energy and Home Design

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

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

  5. 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

  6. p143 Part A 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.

  7. List what appliances are needed in your house: p143 Compare with a partner

  8. 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

  9. How many physics students does it take to light a light bulb? p144 • Using only the items in the bag, make the light bulb glow. • Draw a picture in your notebook • Explain what you think is happening

  10. Electricity model: Section 1DQ: 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

  11. Part B (p599-600) Steps 1-3 only P144 • 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

  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 Section 2 (p606-609) 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 Investigation 2: The Electron ShufflePart A: Modeling a Simple Circuit

  14. 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”

  15. 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

  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 On your own p608 #9Record how the electron shuffle would change under the following conditions: 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 Part B: Modeling a series circuit

  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 Part B (p608) P147-8

  19. Get a stamp • CU (p610) 1-4 Get a stamp • PtoGo (p612-613) 1-4 Get a stamp Draw and complete the chart for #4 (p609)

  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 Electricity model: Section 2

  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 Investigation 3 Series and Parallel Circuits (p614-617)

  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 InvestigationPart A; Modeling a parallel circuit

  23. Round 2 (2 bulbs in parallel): jan-jun go to bulb one jul-dec bulb two p149 • 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:

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

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

  26. Round 3 (3 bulbs in parallel): jan-apr bulb one, may-aug bulb two, sep-dec bulb three p150 • 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

  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) 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?

  28. Three bulbs means each bulb gets 1/3 per second (different amount of current than 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=

  29. 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…)

  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 How does a parallel circuit change under these conditions? (1 volt and 1 amp)

  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 How does a parallel circuit change under these conditions? (3 volt and 1 amp)

  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 How does a parallel circuit change under these conditions? (1 volt and 2 amp)

  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) How does a parallel circuit change under these conditions? (6 volt and 1 amp) 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) How does a parallel circuit change under these conditions? (1 volt and 1 amp) p150

  35. 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 Part B: Comparing series and parallel circuits P150 P151

  36. PHET: Some Properties of Electric Circuits Part VI 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

  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 Electricity model: Section 3

  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 Section 4 (p623) 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 (p629-630) 1-4 CDP 33-2 34-1 p152 investigation

  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 Electricity model: Section 4 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 + 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)

  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 PtoGo (p629)

  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 PtoGo (p630) 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 Section 5 electric power: load limit (p631-643)

  45. 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? p154 Investigation

  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. 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

  47. Below are the appliance ratings: p155 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

  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 Electricity model: Section 5

  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? Section 6 CVR in Parallel and Series: Who’s in control? (p644-659) 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 (p658-659) 1-13 CDP 35-2 35-3 p158 Investigate

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