p1.1 the solar system - singhscience · 2019-11-10 · 1. stars further away than planets 2. stars...

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.