Download Lesson 1 Energy - Tony Ford Science

Tony Ford Science Monday, 1 December 2014 page 1
8.1Lesson1Energy
IntroductionQuestions:
1. Whatisenergy?
2. Wheredowegetitfrom?
3. Whatdoweuseitfor?
4. Canitbestored?
5. Whathappenstoitafterweuseit?
Energyitselfishardtode1inebutweallneedit.
Itcomesfrommatterbutitisnotmatter.
Afamousequation(E=mc2)representstheconversionofmattertoenergyinthesun
andnuclearexplosions.
Whenwesaysomeonehas“lotsofenergy”thenweareaccuratelydescribingwhat
energydoes.Itenablespeopletonotonlylive(eatandbreathe)butalsodowork.In
factanydevicethatusesenergydoeswork.Doingworkmeanstomoveandchange
thingssuchasapersonridingabike,anenginedrivingacarorchemicalsmakingan
explosion.
EnergySources
Theenergyyouusecomesoriginallyfromaplaceorobject.
Naturalsourcesincludethesun,wind,coal,petrol,gas,wavesandtides,hotsprings,
riversandwaterchannels,plantsandanimals,nuclearmaterials.
Arti1icialsourcesincludebatteries,powerstations,matches,lasers.
SomesourcesarecalledRenewableEnergySourcesbecausetheycanbereplacedevery
dayandwon’trunout.
Question:
Whichoftheabovenaturalsourcesarerenewable?
Indecidingtheenergysourcerequiredforeverydayusemanyfactorsneedtobe
consideredincludingrenewability,availability,pollution,ef1iciency,portability.
FormoreinformationonenergysourcesandenergygenerationseeYear6lesson6.7
Generatingelectricity.
EnergyForms
Energycomesintwoforms;PotentialEnergyandKineticEnergy
PotentialEnergyisstoredenergy.
KineticEnergyistheenergyofmotion.
Potentialenergycanbeeasilyconvertedtokineticenergy,whichthendoesworkasit
changesormovesanobject.
ExamplesofPotentialEnergy
1. Gravity–sittingontopofawaterslide,waterstoredinadamonamountain.
Tony Ford Science Monday, 1 December 2014 page 2
2. Chemical–coal,petrolgas,wood,batteries,explosives
3. Nuclear-Uranium
4. Elastic–windupspring,stretchedrubberband
5. StaticElectricity–storedinthundercloud
6. Heat–steamorhotsprings.
Theadvantageofpotentialenergyisthatitcanbetransportedandusedonlywhen
neededandtheenergyisreleased.
ExamplesofKineticEnergy
1. Gravitational-Motionoffalling
2. Throwingorshootingprojectiles
3. Mechanical–motionofmachines
4. Electrical–motionofelectricity
5. Light–raysfromthesun,torches.
6. Heat–movingthroughmaterialsorrisinginair
7. Sound-Movinginwaves
8. Water–Movinginwaves,streams,pipesandcurrents
9. Wind–airmovingfromhightolowpressureorfromafan.
Kineticenergycanmoveorchangeanobjectbutissoonusedupunlessasourceof
energyiscontinuallyproducingit.
DoExperiment:8.2InvestigatingPendulums
Tony Ford Science Monday, 1 December 2014 page 3
EnergyConvertors
Convertorsuseenergy.Theyarecalledconvertorsbecausetheenergyusedischanged
afteruse.
RememberEinstein’sEnergyConservationLaw:
Energycanneverbecreatedordestroyed(exceptinnuclearreactions)
Soaconvertorcanonlychangeenergytoadifferentform.Intheprocessausefulenergy
formisproducedandsomenon-usefulonessuchasheat.
ConvertorEnergyCharts
AllConvertors:
Output
Energy
Input
Energy
Output
Energy
Heat
Energy
Tony Ford Science Monday, 1 December 2014 page 4
Examples:
1. LightBulb
Electrical Energy
Light
Energy
Heat
Energy
2. Human
Chemical
Energy
(Food)
Muscle
Energy
Heat
Energy
3. Car
Mechanical
Energy
(motor)
Chemical
Energy
(Petrol)
4. Explosion
Sound
Energy
Heat
Energy
Kinetic
Energy
(shrapnel)
Chemical
Energy
(Bomb)
Sound
Energy
Light
Energy
5. Microphone
Sound
Energy
(Voice)
Heat
Energy
Electrical
Energy
Heat
Energy
Tony Ford Science Monday, 1 December 2014 page 5
Exercises
Drawenergychartsforthefollowingconvertors:
1. ABurningMatch
2. ANailGun
3. Photosynthesisinaleaf
4. ACrossBow
5. Mobilephonecall
a. Speaking
b. Listening
6. Nameadeviceforthefollowingenergyconversions:
a. Electricity➔Heat
b. Kinetic➔ sound
c. Chemical➔ electrical➔ kinetic
d. Gravitational➔kinetic➔electricity
EnergyEfEiciency
Energyconvertorsarenot100%ef1icient,thatistheydon’tconvertalltheinput
energytousefuloutputenergy.Asshownintheaboveexamples,manyotherforms
ofoutputenergyespeciallyheatisproducedandsomeoftheinputenergyiswasted.
Ef1iciencyismeasured
EfTiciency=Usefuloutputenergyx100%
Inputenergy
Example:LightBulb
ElectricalInput600W LightOutput60W+HeatOutput540W
EfTiciency=60/600x100%=10%efTicient
Question
1. ACaruses1000Jofpetrolenergyandproduces350Jofmechanical(motion)
energy,50Jofsoundenergyand600Jofheat.Howef1icientisthecarformotion?
2. WhyarenewlightscalledLEDlightsalmost100%ef1icient?Howdoesthatsave
electricity?
3. Todayenergysavingapplianceshaveanenergyrating.
Tony Ford Science Monday, 1 December 2014 page 6
a) WhichTVismostef1icient?
b) WhichTVproducesthemostpowerperyear?