P1.1TheSolarSystem
• Geocentricmodel=Ptolemy=explainedtheSun,moonandtheplanetsmoveinorbitsandthatEarthwasatthecentre.
• Heliocentricmodel=Copernicus=sunwasatthecentreandeverythingwentroundtheSun.
• Church=didnotlikeCopernicusidea.
• Galileo=usedtelescopetoproveCopernicuswasright.
Ideasaboutthesolarsystemhavechangedover9me
GalileoobservedJupiter’smoons.ByploEngtheirposiFonsheprovidedmoreevidencefortheheliocentricmodel.
P1.1TheSolarSystemHowdoweknowabouttheSolarSystemandtheMilkyWay?• Telescope=observespace-advantageseemorethenjustwiththe
nakedeye.• LuminousObjects=giveoutlightthattravelsasawave.• Nonluminousobjects=giveoutwavessuchasRadiowavesand
microwaves.Wecandetectthesewaves.
Astelescopesimproved,moreplanetswerediscovered
Comparingdifferentwaysoflookingatspace…1. TelescopesprovidegreatermagnificaFonthanthenakedeye.2. TelescopesprovideconFnuousimages.3. PhotographsprovideapicturefromonemomentinFme.4. Photographscanbestudiedatalaterdate.5. Youneedawaytocapturetelescopeimagestopreservethem.
P1.2RefracFngtelescopesKeywords:• Lens-atransparentblockthatcauseslighttorefract• RefracFon–changesthedirecFonthelighttravelsin.Itoccurswhenlightpassesfromone
substancetoanothere.g.airandglass.• Converginglens(orconvexlens)-iscurvedonbothsides.Thismeansthelightrayscomingoutof
itcometogetheratapoint–theyconverge.• Focalpoint–thepointatwhichlightraysmeet.
MeasuringthefocallengthThefocallengthisfoundbyfocussingadistantobjectonapieceofpaperthroughthelens.Thefocallengthisthedistancebetweenthecentreofthelensandtheimage.Aconverginglensisusedinarefrac9ngtelescopetofocustheimage.Galileo’stelescopewouldhavebeenarefracFngtelescope.
Wavesarealwaysrefractedatboundariesbetweendifferentmaterials
P1.2RefracFngtelescopes
1. ArefracFngtelescopeworksbendinglightthroughalenssothatitformsanimage.
2. LargelensesareneededtoimprovethemagnificaFon.3. TheobjecFvelensfocusesthelighttothefocalpointofthelens.4. Thispointisalsothefocalpointofthemorepowerfuleyepiecelens.5. Theeyepiecelensproducesamagnifiedimageoftheimagefromthe
objecFvelenswhichtheviewercansee.
Youdon’tneedtodrawthisdiagrambutyoudoneedtoexplainhowtheeyepiecelensenlarges
theimage
P1.2RefracFngtelescopesRefrac9on• Lightwaveschangespeedwhenthey
passacrosstheboundarybetweentwosubstanceswithdifferentdensiFes,suchasairandglass.
• Thiscausesthemtochangedirec9onandthiseffectiscalledrefrac9on.
• Thereisonespecialcaseyouneedtoknow.RefracFondoesn'thappeniftheycrosstheboundaryatanangleof90°-inthatcasetheycarrystraighton.
normal
normal
incidentray
refractedray
RefracFngtelescopesneedtobelonginordertohavelargemagnificaFon.
P1.3Lenses
ConverginglensesTheirmagnificaFonisaffectedby• Howcurvedtheyare• HowclosetogetherthelensesareArealimagecanbeprojectedontoascreen.Avirtualimageisseenonamirrorandcannotbeprojected.
Refrac9ngtelescope.
Inordertocollectasmuchlightaspossible,theobjecFvelensneedsalargediameter.Largelensesareverydifficulttomakeandsoareveryexpensive.ReflecFngtelescopesovercomethisbyusingrelaFvelycheapmirrorsastheirobjecFve.Thesecanbemadeextremelylarge.
P1.4reflecFngtelescope
Howtheywork…• ReflecFngtelescopeshavea
curvedmirrorinsteadofanobjecFvelens.
• Theprimarymirrorfocusesparallellightraysfromadistantobject.
• Theeyepiecelensmagnifiesthisimage
P1.5WavesKeydefiniFon:WavestransferenergyandinformaFonwithouttransferringmader.
Keywords:Wavelength–Thedistancefromonepeak(ortrough)tothenext.Frequency–Thenumberofwavespassingapointpersecond.Amplitude–themaximumdistanceofparFclesinawavefromthenormal.
2equaFonsyouneedtobeabletouse:Wavespeed=frequencyxwavelength
Wavespeed=distance/Fme
P1.5WavesLongitudinalwavese.g.soundwaves.Transversewavese.g.electromagneFcwaves,don’tneedamediumtotravelthrough.Seismicwavescanbelongitudinal(whenthecrustmovesbackandforth,ortransversewhenthecrustmovesupanddown.
P1.6Beyondthevisible• Herschelputdarkcoloured
filtersontelescopetoobservetheSun.
• HenoFcedthatthefiltersheatedupthetelescopetodifferentextents.
• Heusedaprismtotestthisandputthermometersineachcolouroflight.
• Ashemovedfromviolettored,thetemperatureincreased.
• Justbeyondtheredwasevenhoder.
• Hediscoveredinfraredwaves.
• RiMerinvesFgatedthevioletendofthespectrum.
• Heputsilverchlorideateachendofthespectrum.Itturnedblackmorequicklyatthevioletendthantheredend.
• Itturnedblackevenmorequicklyjustbeyondtheviolet.
• Thiswascalledultravioletwaves.
AllelectromagneFcwavesaretransverse.TheytransmitenergyatrightanglestothedirecFonofthevibraFon.
KnowthesetwoscienFstsandtheir
work!
P1.7TheElectromagneFcSpectrumLearntheseinorder
• AllelectromagneFcwavesaretransverse.• AllelectromagneFcwavestravelatthesamespeedina
vacuum.• TheelectromagneFcspectruminconFnuousfromradio
wavestogammarays• ThedifferentradiaFonsaregroupedinorderof
decreasingwavelengthandincreasingfrequency
P1.8electromagneFcdangers• Thehigherthefrequencythemoreenergythatthey
carry.
• High-frequencyelectromagneFcwaves,suchasgammarays,arepotenFallymoreharmfulbecausetheyhavemoreenergy.
Allwavestransferenergy.
Bodiesaremadeofmostlywater-wavescanheatwater.
Atthemomentthereisnoevidencetosupportmobilephonescouldbeharmfultothebody
IRradiaFonusedingrillsandtoasters.OurskinabsorbsIR=makesuswarm.Toomuchcancauseburnstotheskin.
Wave Effectonthebody
Microwaves InternalheaFngofbodycells
Infrared Burnsskin
Ultraviolet DamagetosurfacecellsandeyesleadingtoskincancerandeyecondiFons
X-raysandgammarays
CausesmutaFonsanddamagetocellsinthebody
P1.9usingelectromagneFcradiaFon
Electromagne9cRadia9on Use
Radiowaves BroadcasFng,communicaFonandsatellitetransmissions
Microwaves Cooking,communicaFonsandsatellitetransmissions
Infrared Cooking,thermalimagingshortrangecommunicaFon,opFcalfibres,televisionremotecontrols,securitysystems
Visible Vision,photography,illuminaFon
Ultraviolet Securitymarking,fluorescentlamps,detecFngforgedbanknotes,disinfecFngwater
X-rays Observinginternalstructureofobjects,airportsecurityscanners,medicalx-rays
Gammarays Sterilisingfoodandmedicalequipment,detecFonofcancer,treatmentofcancer
P1.10IonisingradiaFon• IonisingradiaFonisemidedalltheFmebyradioacFvesources.
• IonisingradiaFonincludesalphaandbetaparFclesandgammarays.
• ThesethreetypesofionisingradiaFontransmitenergyandcanalldamagecells.
• Itiscalledionisingasitremoveselectronsfromatomstoformions.
• IonsareveryreacFveandiftherearealotofthemincells,theycandamageDNA.
P1
Topic3WavesandtheUniverse
P1.11TheUniverse
Keywords• Star–alargeballofgasthatproducesheatandlightenergyfromfusionreacFons• MilkyWay–Thenameofourgalaxy• Nebula–acloudofgasinspace.Someobjectsthatlooklikenebulaeareactuallyclusterofstarsor
othergalaxies• Solarsystem–anareaofspaceinwhichobjectareinfluencedbytheSun’sgravity• Galaxy–agroupofmillionsofstarsheldtogetherbygravity• Universe–allthestars,galaxiesandspaceitself
Facts:• Themoonis30‘earths’away• Thesunis11,000‘earths’away
AncientastronomersobservaFons/ideas:1. Starsfurtherawaythanplanets2. Starsinashellaroundearthatthesamedistance3. Sawpatchesof‘fuzz’light(nebulae)4. Bandoflightacrossthesky=MilkyWayGalileo1. Usedbasictelescopesbutcouldonlysee6planetsModernobserva9ons:1. 8planetsplusdwarfplants,manymoonsandasteroids2. Sunisoneofmillionsofstarsinthegalaxy(MilkyWay)3. Billionsofothergalaxies4. Allthesegalaxiesmakeuptheuniverse
P1.12,1.13–SpectrometersandExploringtheUniverseKeywords• Spectrum–Therangeofcoloursbetweenredandvioletobtainedwhenwhitelightissplitusingaprism.• Spectrometer–Aninstrumentthatcansplituplighttoshowthecoloursofthespectrum• Visiblelight–ElectromagneFcwavesthatcanbedetectedbythehumaneye• Electromagne9cspectrum–TheenFrefrequencyrangeofelectromagneFcwaves• X-ray–electromagneFcradiaFonthathasashorterwavelengththanUVbutlongerthangammarays• Ultraviolet–electromagneFcradiaFonthathasashorterwavelengththatvisiblelightbutlongerthanXrays
FactsLightfromthesunisamixtureofdifferentcolours.Eachcolourlighthasadifferentwavelengthandfrequency.TheycanbesplitwithaprismorsomethingwithlotsoflineslikeaCDorDVD.AdevicethatcansplitdifferentwavelengthsiscalledaspectrometerTheatmosphereabsorbssomewavelengthssotheyneverreachearth.
Telescopes• Earlytelescopesdetectedonlyvisiblelight• ModerntelescopesdetectallpartsoftheElectromagnecFcspectrum(see
diagramabove)• HubbleSpacetelescope–inorbitaroundearthsince1990
– Clearimagesasitisabovetheatmospheresodoesnotgetinterferencefromcloudsanddust
P1.14–AlienLife?
Keywords–(allfrompreviousslideB1.12and1.13alsoneeded)
• Landers–aspacevehiclethatlandsonaplanetoramoon• Spaceprobes–aspacevehiclethatcanbeputintoorbitaroundaplanetormoon,orparachuteddownthroughthe
atmosphere.• Rovers–aspacevehiclethatcanmoveaboutonaplanetormoon.• SETI-SearchforExtraterrestrialIntelligence)
Inves9ga9ngtheSolarSystem
Earthistheonlyplacewhereweknowlifeexists.• Vikinglandershavebeentomars• Analysedsoilforevidenceoflife• Noevidencediscovered
• Waterisneededforlife• SpaceprobesorbiFngMarshavedetecFng
channelcausedbywaterflowing
• Roversusedtotakecloseupphotographs
BeyondtheSolarSystem• Planetsdiscoveredorbi9ngotherstars• Theyaretoofarawaytogetclearimages• Oxygenintheatmospherewouldbeproofof
life.
SETI
• Aprojectthatanalysesradiowavescomingfromspace.
• Looksforsignalsthatcouldbefromintelligentbeing.
• Nomessagesdetectedyet.
P1.15Lifecyclesofstars
Keywords• Protostar–Acloudofgasdrawntogetherbygravitythathasnotyetstartedto
produceitsownenergy.• Fusionreac9on–whenthenucleioftwoatomsjointogetherandreleaseenergy• Redgiant–Astartthathasusedupallthehydrogeninitscoreandisnowusing
heliumasafuel.Itisbiggerthananormalstar.• Whitedwarf–Averydensestarthatisnotverybright.Aredgiantturnsintoa
whitedwarf.• Supernova–Anexplosionproducedwiththecoreofaredsupergiantcollapses.• RedSupergiant–Astarthathasusedupallthehydrogeninitscoreandhasa
massmuchhigherthantheSun.• Blackhole–Coreofaredsupergiantthathascollapsed.Onlycreatedwhenthe
remainingcorehasamass3-49mesthatofthesun.• NeutronStar–Coreofaredsupergiantthathascollapsed.
Nebula• Sunsremainstablefor
billionsofyears.• Asthenebulaheatupit
glows• Moremassadracted
whichincreasesgravityandcompressesmaterialintoaprotostar.
Protostar• Temperaturesand
pressureincrease.• Hydrogennucleifuseto
makehelium.• FusionreacFonsrelease
energyasEMradiaFon.MAINSEQUENCEofthelifecycle
Massivestars• Hoderandbrighter• FusionreacFonsarefaster• Becomeredsupergiants• Rapidlycollapsesandexplode
(supernova)
RedGiant• OncemostHydrogenfusedthestarisnothot
enoughtowithstandgravityandcollapses• FormsaRedgiant
Supernova• Outerlayerscastoffandexpandoutwards• TwoopFons1. If3-4Fmesheavierthanthesun=Blackhole(gravitysostrong
notevenlightcanescape)2. Anythingsmallerformsaneutronstar.
WhiteDwarf• StarisRedgiantforbillionsofyears• Gasshellthrownoffsoitcollapsesintoawhite
dwarf.• Coolsslowlytobecomeablackdwarf.P1.15Lifecyclesofstars
(cont’d)
P1.16TheoriesabouttheUniverse
Lightmovingawayfromusisdetectedwitha
longerwavelengththanexpected.ItisshitedtowardstheRedendofthespectrum=REDSHIFTLightfromothergalaxiesdoesthisshowingtheyaremovingawayfromus.
UNIVERSEISEXPANDING
STEADYSTATETHEORY1. Universealwaysexistedandisexpanding2. NewmaderconFnuouslycreatedsoitalways
looksthesame3. Redshitsupportsthistheoryaswellasthe
BigBangtheory.4. Nolongeracceptedtheory
BIGBANGTHEORY1. Start-Tinypointofconcentratedenergy
billionsofyearsago2. Allmaderexistedatthispoint3. Expandingfromthispoint4. Gravitycausedmadertoclumpforming
stars5. CosmicMicrowaveBackground(CMB)
radiaFon(microwavesignalsfromalloverthesky)providedprooffortheBigBangTheory
6. Acceptedtheorytoday
P1.17–Redshit
KeywordsRedShii–wavesemidedbysomethingmovingawayfromanobserverhavetheirwavelengthincreasedandfrequencydecreasedcomparedtowavesfromastaFonaryobject.DopplerEffect–thechangeinpitchofasoundcomingfromamovingsourcePitch–whetherasoundishighorlow
1. Soundwavesbehindamovingsourcebecomestretchedmakingthefrequencylowerandthewavelengthlonger.SimilareffectoccursinREDSHIFT
2. VISIBLESPECTRUMcontainsgaps.Iftheyareredshiiedthestarismovingawayfromus
3. Furtherawaygalaxiesaremovingthefastest
P1
Topic4WavesandtheEarth
P1.18–Infrasound
KeywordsFrequency–numberofcompletewavesthatpassapointinonesecondHertz–unitofmeasurementforfrequencyLongitudinalwaves–thedirecFonofenergyisparalleltothedirecFonofvibraFonwhichcausesthemInfrasound–soundwithfrequencybelow20Hz(cannotbeheard)
Usesofinfrasound1. Studyinganimalmovements
a) Elephants,whalesandgiraffescommunicateusinginfrasoundb) Animalscanbetrackedindifficultareas(forests)
2. Monitoringvolcanoesa) Infrasoundtravelsalongwayb) UsedtomonitorvolcanoesinremotelocaFonsfromadistance
3. DetecFngmeteorsa) Someenteratmosphereunseenb) Helpsusdeterminehowmanyenterandtherisksofimpact
P1.19–Ultrasound
Ultrasound• Humansdetectsoundwavesbetween20–20,000Hz• Above20,000Hz=Ultrasound• Someanimalsuseittocommunicate(dolphins)
Sonar• Usedbysomeanimals(bats)todetectobstacles• Ultrasoundwavesmadebyanimalsreflectasechoes• Usedbyhumansinshipstodetectfish,seadepthEquaFon
Distance(m)=speed(m/s)x9me(s)UltrasoundScan• Makeimagesofthingsinsidethebody• Exampleofuse–toscananunbornbabytocheck
development– differentpartsofthebabyreflectthesoundindifferent
waystocreatetheimageonthescreen.
KeywordsUltrasound–soundwaveswithafrequencyabove20,000Hz,whichistoohighforthehumaneartodetect.Sonar–awayofdeterminingdistancetoanobjectbyFminghowlongittakesforapulseofultrasoundtobereflected.Reflected–whenawavebouncesoffaboundarybetweentwomaterials
P1.20–Seismicwaves
• Movementsinsidetheearthcauseseismicwavestobetransmided
• Whenwavesreachthesurface=groundshakes• Seismometersdetectthesewaves• Placewheretheoriginalmovementorfracture
occurs=focusandtheepicentreisthesurfacedirectlyabovethefocus.
Inves9ga9ngtheEarth• ScienFstsinvesFgatewavesbutseEng
controlledexplosionsordroppingmassesfromatruck
• ThewavesreflectandrefractgivinginformaFonabouttherocksbelow
• Usedtolookfrooilorlocatechangesinrocktype.
• Seismicwaves–Wavesproducedbyanexplosionorearthquakeandwhichtravelthroughtheearth.
• Focus(ofearthquake)–theplacewhereanearthquakebegins(usuallyunderthesurface)
• Epicentre–ThepointonthesurfaceoftheEarthdirectlyabovethefocusofanearthquake
• Pwaves–Longitudinalseismicwavesthattravelthroughtheearth• Swaves–Transverseseismicwavesthattravelthroughtheearth
P1.21and1.22–EarthquakesandDetecFngEarthquakes
KeywordsTsunami–ahugewavecausedbyanearthquakeorlandslideontheseabedTectonicPlates–PiecesofthesurfaceoftheEarth,whichcanmovearoundveryslowlyConvec9oncurrents–acurrentcausedbypartsofafluidbeingatadifferenttemperatureandsoadifferentdensitytotherestofthefluid.Detec9ngearthquakes1. Networkofseismometersaround
theworld2. Calculatethearrival9mesof
differentwaves(PandS)toworkoutepicentreofearthquake
Predic9ngearthquakesandtsunamis1. Useplateboundariestopredictlikely
loca9ons2. Cannotmeasuretheforcesmoving
platesorthefricFonwhichmakespredic9ngearthquakesdifficult.
3. Anearthquakeundertheseacausesahugewave(Tsunami)
4. Tsunamiwarningsystemsincludepressuresensorstodetectwaves
5. Seisometertracesdonotgivewarning6. Tsunamistravelatdifferentspeedsso
thiscangiveanopportunityforwarningstobegiven.
Earthquakes1. Outerlayerofearth=tectonicplates2. Theyarepushedslowlyby
convec9oncurrentsinthemantle3. FricFonbetweenthemstopsthe
movementunFltheforcegetsbigenoughandajerkhappens=earthquake
1.23Renewableresourcesforelectricity
Keywords:• Current–theflowofcharge.• Voltage–electricalpressuregivingameasureoftheenergytransferred.
• Renewableenergysource–willnotrunout.
Typeofenergy Advantages Disadvantages
Solar • PotenFallyinfiniteenergysupply.• Singledwellingscanhaveownelectricitysupply.• Noharmfulgasesproduced.
• ManufactureandimplementaFonofsolarpanelscanbecostly.
Wind • Canbefoundsingularly,butusuallymanytogetherinwindfarms.• PotenFallyinfiniteenergysupply.• Noharmfulgasesproduced.
• ManufactureandimplementaFonofwindfarmscanbecostly.• Somelocalpeopleobjecttoon-shorewindfarms,arguingthatitspoilsthecountryside.
Tidal • IdealforanislandsuchastheUK.• PotenFaltogeneratealotofenergy.• Tidalbarragecandoubleasabridge,andhelppreventflooding.• Noharmfulgasesproduced.
• ConstrucFonofbarrageisverycostly.• Onlyafewestuariesaresuitable.• OpposedbysomeenvironmentalgroupsashavinganegaFveimpactonwildlife.• MayreduceFdalflowandimpedeflowofsewageouttosea.
Wave • Idealforanislandcountry.• MorelikelytobesmalllocaloperaFons,ratherthandoneonanaFonalscale.• Noharmfulgasesproduced.
• ConstrucFoncanbecostly.• Maybeopposedbylocalorenvironmentalgroups.
Geothermal • PotenFallyinfiniteenergysupply.• Usedsuccessfullyinsomecountries,suchasNewZealandandIceland.• Noharmfulgasesproduced.
• CanbeexpensivetosetupandonlyworksinareasofvolcanicacFvity.• GeothermalandvolcanicacFvitymightcalmdown,leavingpowerstaFonsredundant.• Dangerouselementsfoundundergroundmustbedisposedofcarefully.
HydrologicalorHydroelectricPower(HEP)
• Createswaterreservesaswellasenergysupplies.• Noharmfulgasesproduced.
• Costlytobuild.• CancausethefloodingofsurroundingcommuniFesandlandscapes.• Damshavemajorecologicalimpactsonlocalhydrology.
P1.24Non-renewableresourcesTypeoffuel Advantages DisadvantagesCoal(fossilfuel) • Ready-madefuel.
• ItisrelaFvelycheaptomineandtoconvertintoenergy.• Coalsupplieswilllastlongerthanoilorgas.
• Whenburnedcoalgivesoffatmosphericpollutants,includinggreenhousegases.
Oil(fossilfuel) • Oilisaready-madefuel.• RelaFvelycheaptoextractandtoconvertintoenergy.
• Whenburned,itgivesoffatmosphericpollutants,includinggreenhousegases.• Onlyalimitedsupply.
Naturalgas(fossilfuel)
• Gasisaready-madefuel.• ItisarelaFvelycheapformofenergy.• It'saslightlycleanerfuelthancoalandoil.
• Whenburned,itgivesoffatmosphericpollutants,includinggreenhousegases.• Onlylimitedsupplyofgas.
Nuclear • AsmallamountofradioacFvematerialproducesalotofenergy.• RawmaterialsarerelaFvelycheapandcanlastquitealongFme.• Itdoesn'tgiveoffatmosphericpollutants.
• Nuclearreactorsareexpensivetorun.• Nuclearwasteishighlytoxic,andneedstobesafelystoredforhundredsorthousandsofyears(storageisextremelyexpensive).• LeakageofnuclearmaterialscanhaveadevastaFngimpactonpeopleandtheenvironment.TheworstnuclearreactoraccidentwasatChernobyl,Ukrainein1986.
P1.26GeneraFngElectricityFactorsthataffectthesizeofaninducedcurrent:• Usingacoilofwireorincreasingthenumberofturnsonthecoil.
• Useanironcore.• Useastrongermagnet.• Movethewirefaster.FactorsthataffectthedirecFonofaninducedcurrent:• ThedirecFonofthemovementofthewire.• ThedirecFonofthemovementogthemagnet.
P1.26GeneraFngElectricity
Keywords:• DirectCurrent(D.C.)–AcurrentthatflowsinonedirecFon.• AlternaFngCurrent(A.C)–AcurrentwhosedirecFonchangesmany
Fmesasecond.• ElectromagneFcInducFon–Theprocessofmakingacurrentinawire
asitispassedthroughamagneFcfield.• ForaconFnuouscurrent,thewireorthemagnetmustbeconFnually
moving.
• InapowerstaFon,alargecurrentneedstobeinduced.
• Electromagnetsareusedastheyaremorepowerfulthanpermanentmagnets.
P1.26GeneraFngElectricity
AGenerator
• Currentisinducedinthecoil.Andtransferredtoacircuitthroughtheslipringswhichtouchcarbonbrushes.
• AsthecoilturnsthedirecFonoftheinducedcurrentchanges.
• AlternaFngCurrent(A.C.)isinduced
P1.26GeneraFngElectricity
ADynamo
• Usedtoproduceelectricitytopowercyclelights.
• Magnetspinsinsideacoilofwire
• Acurrentisinduced.• Directcurrent(D.C)• Otherexamplesarewind
uptorchesorradios.
P1.27TransmiEngElectricity
Keywords:• Transformers–changethesizeofanalternaFngvoltage.
• Stepuptransformer–increasesthevoltage• Stepdowntransformer–decreasesthevoltage
Electricityistransmidedathighvoltagesasitincreasesefficiencybyreducingheatlossinthepowerlines.
P1.27TransmiEngElectricity
• Atransformerconsistsoftwocoilswrappedaroundanironcore.
• Electricityissuppliedtotheprimarycoilandobtainedinthesecondarycoilatadifferentvoltage.
Youneedtobeabletousethisformulatoworkouttheturnsofthevoltage:Trytheseexamples…
P1.27TransmiEngElectricity
Hazardsofelectricaltransmission• Highvoltagesarelikelytokill.
Voltageincreasedto400,000Vtoreduce
heatloss
Voltagereducedto33,000Vforfactories
Voltagereducedto230/240Vforhomes
P1.28PayingforElectricityKeywords:• Power–theenergy
transferredpersecond.Measuredinwads(W)
• EnergyfromthemainssupplyismeasuredinKilowad-hours(Kwh)
What is the power if the voltage is 12V and the current is 5A?
power = 5 × 12 = 60W
Formula1
3formulaeyouneedtoknow…
P1.28PayingforElectricity• Electricitymetersmeasurethe
numberofunitsofelectricityusedinahomeorotherbuilding.Themoreunitsused,thegreaterthecost.ThecostoftheelectricityusediscalculatedusingthisequaFon:
• cost=power(kW)×Fme(hour)×costof1kWh(pence)
How much energy is used by a 2000W appliance running for 60 seconds?
power = 2000 × 60 = 120000
Anelectricfireneeds2kW.Itisswitchedonfor3hours.IfeachkWhcosts10p,howmuchdoesitcosttorunthefire?cost=power×Fme×costof1kWh=2kW×3h×10p=60p
Formula2Formula3
P1.30ReducingenergyuseDisadvantagesoflowenergyappliances:• iniFalcost• useofextraresourcestomanufacturenewdevice
• costofdisposalofolddevice.Advantagesoflowenergyappliances:• costefficiency• savingenergyandresources.
P.31EnergyTransfersEnergycannotbecreatedordestroyed.Itcanonlybetransferredfromonetypetoanother.
8typesofenergy:1. Heat2. Light3. Sound4. Electrical5. Chemical6. NuclearpotenFal7. PotenFal(GravitaFonalorelasFc)8. KineFc
Energyinput=Energyoutput
P1.31EnergyTransfers
• Energytransferdiagramsshowhowenergyistransferred.
• Thewidthofthearrowsrepresentstheamountofenergytransferredateachstage.
Example–anoldstylelightbulb.100Jofenergyaresuppliedtothebulb.10Jareusefullytransferredaslight.90Jaretransferredasheat.
P1.32Efficiency
Keyword:• Efficiency–theproporFonofenergytransferredintouseful
forms.
Example–anewstylelightbulb.100Jofenergyaresuppliedtothebulb.75Jareusefullytransferredaslight.25Jaretransferredasheat.=(75/100)x100%=75%
P1.33HeatRadiaFon
• BlackcarsheatupmorethanothercarsbecausetheyabsorbmoreradiaFonfromthesun.
• BlackisthebestcolourforradiaFngheatandabsorbingheat.
P1.34TheEarth’stemperature
Forasystemtobeataconstanttemperature,itneedstoabsorbthesameamountofpowerasitradiatesout.