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better hope – brighter future
AQAENERGY–part1
EnergyCon
servationan
dDissipation
Energystoresand
changes
System Anobject orgroupofobjectsthatinteracttogether EG:Kettleboiling water.
Energy storesKinetic,chemical,internal(thermal),
gravitationalpotential, elasticpotential,magnetic,electrostatic,nuclear
Energyisgainedorlostfromtheobjectordevice.
Waystotransferenergy
Light,sound,electricity,thermal,kineticarewaystotransferfromonestoreto
anotherstoreofenergy.
EG: electricalenergytransferschemicalenergyintothermalenergytoheatwaterup.Unit Joules(J)
Efficiency=UsefuloutputenergytransferTotalinputenergytransfer
Efficiency=UsefulpoweroutputTotalpowerinput
HIGHER:efficiencycanbeincreasedusingmachines.
Prefix Multiple Standardform
Kilo 1000 103
Mega 1000000 106
Giga 100000000 109
Units
SpecificHeatCapacity JoulesperKilogramdegreeCelsius(J/Kg°C)
Temperaturechange DegreesCelsius( °C)
Workdone Joules(J)
Force Newton(N)
Distancemoved Metre (m)
Power Watts(W)
Time Seconds(s)
Kineticenergy
Energy storedbyamovingobject
½XmassX(speed)2½mv2
ElasticPotentialenergy
Energystoredinastretchedspring,elasticband
½ XspringconstantX(extension)2½ke2
(Assumingthelimitofproportionalityhasnotbeenexceeded)
GravitationalPotentialenergy
Energygainedbyanobjectraisedabovetheground
MassXgravitationalfieldstrengthXheightmgh
Dissipate
Toscatterinalldirectionsortousewastefully
Whenenergy is‘wasted’,itdissipatesintothe
surroundingsasinternal(thermal)energy.
Work
Doingworktransfersenergyfromonestoreto
another
Byapplyingaforcetomoveanobjecttheenergystoreischanged.
Workdone=ForceXdistancemovedW=Fs
Power Therateofenergytransfer
1 Jouleofenergypersecond =1wattofpower
Power=energytransfer÷ timeP=E÷ t
Power=workdone÷ time,P=W÷ t
Energy
pathwaysMechanical Forceactsuponanobject
Electrical Electriccurrentflow
Heat Temperaturedifferencebetween objects
Radiation Electromagneticwaves orsound
Efficiency Howmuchenergyisusefullytransferred
Changeinthermalenergy=massXspecificheatcapacityX temperaturechange ∆E=mXc X ∆θ
SpecificHeat
Capacity
Energyneededtoraise1kgof
substanceby1°C
Dependson:massofsubstance,whatthesubstanceis andenergyputintothesystem.
Principleofconservationofenergy
Theamountofenergy
alwaysstaysthesame.
Energycannotbecreatedordestroyed,onlychangedfromonestoretoanother.
Units
Energy(KE,EPE,GPE,thermal) Joules(J)
Velocity Metrespersecond(m/s)
Springconstant Newtonpermetre(N/m)
Extension Metres(m)
Mass Kilogram(Kg)
Gravitationalfieldstrength Newtonperkilogram(N/Kg)
Height Metres(m)
Reducingfriction- usingwheels,applyinglubrication.Reducingairresistance–
travellingslowly,streamlining.
Frictionalforcescauseenergytobetransferredasthermalenergy.Thisis
wasted.
HIGHER:Whenanobjectismoved,
energyistransferredbydoingwork.
Closedsystem
Nochangeintotalenergyin
system
Opensystem
Energycandissipate
Usefulenergy
Energytransferredandused
Wastedenergy
Dissipatedenergy,storedlessusefully
Workdone=ForceXdistancemoved
Waystoreduce‘wasted’energy
Energytransferredusefully
Insulation,streamlinedesign,lubricationofmovingparts.
better hope – brighter future
AQAENERGY–part2
Non-renewableenergyresource
Thesewillrunout.Itisafinite reserve.Itcannotbe
replenished.
e.g.Fossilfuels (coal,oilandgas)andnuclearfuels.
Renewableenergyresource
Thesewillneverrunout.Itisaninfinite reserve.Itcanbereplenished.
e.g.Solar,Tides,Waves,Wind,Geothermal,Biomass,Hydroelectric
Powerstation– NB:Youneedtounderstandtheprinciplebehindgeneratingelectricity.Anenergyresourceisburnttomakesteamtodriveaturbinewhichdrivesthegenerator.
NationalGrid
GlobalEnergy
Resources
Energyresource Howitworks Uses Positive Negative
FossilFuels(coal, oiland
gas)
Burnt toreleasethermalenergyusedtoturnwaterintosteamtoturn
turbines
Generatingelectricity,heatingandtransport
Provides mostoftheUKenergy.Largereserves.Cheaptoextract.Usedintransport,heatingand
makingelectricity.Easytotransport.
Non-renewable. Burningcoalandoilreleasessulfur dioxide.Whenmixedwithrainmakesacidrain.Acidraindamagesbuildingandkills
plants.Burningfossilfuels releasescarbondioxidewhichcontributestoglobalwarming.Seriousenvironmentaldamageifoilspilt.
Nuclear Nuclearfissionprocess GeneratingelectricityNo greenhousegasesproduced.
Lotsofenergyproducedfromsmallamountsoffuel.
Non-renewable.Dangersofradioactive materialsbeingreleasedintoairorwater.Nuclearsitesneedhighlevelsofsecurity.Startupcostsanddecommissioncostsveryexpensive.Toxicwasteneedscarefulstoring.
Biofuel Plant matterburnttoreleasethermalenergy
Transportandgeneratingelectricity
Renewable.Asplantsgrow,theyremovecarbondioxide.Theyare
‘carbonneutral’.
Large areasoflandneededtogrowfuelcrops.Habitatsdestroyedandfoodnotgrown.Emits carbondioxidewhenburntthusaddingto
greenhousegasesandglobalwarming.
TidesEverydaytidesriseandfall,sogenerationofelectricitycanbe
predictedGeneratingelectricity
Renewable.Predictabledue toconsistencyoftides.No
greenhousegasesproduced.
Expensivetosetup.Adamlikestructureisbuiltacrossanestuary,alteringhabitatsandcausingproblemsforshipsandboats.
Waves Upanddownmotionturnsturbines Generatingelectricity Renewable.Nowasteproducts. Canbeunreliabledependsonwaveoutputaslargewavescanstopthepistonsworking.
Hydroelectric Fallingwaterspinsaturbine Generatingelectricity Renewable.Nowasteproducts. Habitatsdestroyed whendamisbuilt.
Wind Movementcausesturbine tospinwhichturnsagenerator Generatingelectricity Renewable.Nowasteproducts. Unreliable– wind varies.Visualandnoisepollution.Dangerousto
migratingbirds.
SolarDirectlyheatsobjectsinsolarpanelsorsunlightcaptured inphotovoltaic
cells
Generatingelectricityandsomeheating Renewable.Nowasteproducts. Makingandinstallingsolarpanelsexpensive. Unreliableduetolight
intensity.
GeothermalHotrocksunderthe groundheatswatertoproducesteamtoturn
turbine
Generatingelectricityandheating
Renewable.Clean.Nogreenhousegasesproduced.
Limitedtoasmallnumberofcountries.Geothermal powerstationscancauseearthquaketremors.
Transport Petrol,diesel,keroseneproducedfromoil
Usedincars,trainsandplanes.
Heating Gasandelectricity Usedinbuildings.
Electricity Mostgeneratedbyfossilfuels
Usedtopowermostdevices.
Usingfuels
Energyresources
Powerstation
Generateselectricity
Fuelburntreleasing
thermalenergy
Waterboilsintosteam
Steam turnsturbine
Turbineturnsgenerator
Generatorinducesvoltage
NationalGrid
Transportselectricity across
UKPowerstation Step-up
transformer Pylons Step-downtransformer
House,factory
Energydemandisincreasingas
populationincreases.
Renewableenergymakesupabout20%ofenergyconsumption.
Fossilfuelreservesarerunningout.
Usingrenewableenergywillneedtoincreasetomeetdemand.
better hope – brighter future
AQAElectricity
Circuitsymbols
Serie
sand
parallel
circuits
Cell Battery Switch Lamp Ammeter Voltmeter
Storeofchemicalenergy
Two ormorecellsinseries
Breakscircuit,turning
currentoff
Lightswhencurrentflows
Measurescurrent
Measurespotentialdifference
Current,potentialdifferenceandresistance
Energytransfers
Domesticusesandsafety
Staticelectricity
Current Flowofelectricalcharge
Ampere(A)
Potentialdifference(p.d.)
Howmuchelectricalworkis donebyacell Volts (V)
Charge Amountofelectricitytravelling inacircuit
Coulombs(C)
Diode LED LDR Fuse Resistor Variableresistor Thermistor
Currentflowsoneway
Emitslightwhencurrentflows
Resistancelowin
brightlight
Meltswhen
currentistoohigh
Affectsthesizeofcurrentflowing
Allowscurrenttobevaried
Resistancelowathigh
temp
3pinplug
Live- Brown Carriesp.d frommainssupply.
p.d betweenliveandearth=230V
Neutral- Blue Completesthecircuit. p.d.= OV
Earth– GreenandYellowstripes
Onlycarriescurrent ifthereisafault. p.d.=0V
Seriescircuit
Currentisthesameinallcomponents.
Totalp.d.frombatteryissharedbetweenallthecomponents.
Totalresistanceisthesumofeachcomponent’sresistance.
Parallelcircuit
Total currentisthesumof
eachcomponent’s
current.
p.d.acrossallcomponentsisthesame.
Totalresistanceislessthanthe
resistancevalueofthesmallest
individualresistor.
Electron
scarrycurrent.
Electron
sarefreeto
moveinm
etal.
‘Earthing’asafetydevice;Earthwirejoinsthemetalcase.
Charge=CurrentXtime Q=IXt
Series Parallel
Acircuitwithoneloop
Acircuitwithtwoormoreloops
Changing
curren
t Change thep.d.ofthecells
Addmorecomponents
Ammeter Setupinserieswithcomponents
Voltmeter Setupparallel tocomponents
Resistance(Ω)
A measurementofhowmuchcurrentflowisreduced
Thehighertheresistance, themoredifficultitisforcurrenttoflow.
Increasingresistance, reducescurrent.
Increasingvoltage, increasescurrent.
Resistance=Potentialdifference
÷ Current
R=V÷ I
Ohmicconduct
or
Ataconstant temperature,currentisdirectly
proportionaltothep.d.acrosstheresistor.
Filamentlamp
Ascurrentincreases,theresistanceincreases. Thetemperatureincreasesas
currentflows.
DiodeCurrentflowswhenp.d.flowsforward.Veryhighresistanceinreverse.
Current–Potential
differencegraphs
Controllingcurrent
CurrentandCharge
Alternatingcurrent Directcurrent
p.d.switchesdirectionmanytimesasecond,currentswitchesdirection
p.d.remainsinonedirection,
currentflowsthesamedirection
Generator. Cellorbattery.
Thermistor LDR
Resistancevarieswithtemperature
Resistancevarieswithlightintensity
Resistancedecreasesastemperature increases.
Resistancedecreasesaslight increases.
Totalp.d Ifcells arejoinedin
series,addupindividualcellvalues
PHYSICSonly
Power(W)=potentialdifferenceXcurrent R=VXI
P=I2 XRPower=(current)2 XresistanceWorkisdonewhenchargeflowing.
Energytransferred=PowerXtime E=PXt
National
Grid
Distributes electricitygeneratedinpowerstationsaroundUK
Step-up transformers Step-downtransformers
Increasevoltage,decreasecurrent
Decreasevoltage,increasecurrent
Increasesefficiency,reducesheatloss.
Makessaferforhouses.
Static
electricity Electrical
chargeisstationary
When twoinsulatingmaterialarerubbedtogether,electronsmovefromonematerialtotheother.Mainssupply
Frequency50Hz,230V
Likecharges Repel
Unlikecharges Attract
Shocks
Walkingoncarpetcausesfriction.Electronsmovetothepersonandchargebuildsup.Whenthepersontouchesametalobject,theelectronsconductaway,makingaspark.
Electricfields Charged objectscreateelectricfields
aroundthem.Strongestclosesttotheobject.Thefielddirectionisthedirectionofforceonapositivecharge.Addmorechargeincreasesfieldstrength.
better hope – brighter future
AQAPARTICLEMODEL
OFMATTER
Pressure
Changeofstate
Internalenergyandenergytransfers
Density=mass÷ volume.
State Particlearrangement Properties
SolidPackedinaregular
structure.Strongforcesholdinplacesocannotmove.
Difficulttochangeshape.
Liquid Closetogether,forceskeepcontactbut canmoveabout.
Canchangeshapebutdifficulttocompress.
Gas
Separatedbylargedistances.Weakforcesso
constantlyrandomlymoving.
Canexpandtofillaspace,easytocompress.
Particlemodel
Changeinthermalenergy=massXspecificheatcapacityXtemperaturechange.
Energyneeded=massX specificlatentheat.
P =m÷ V
Units
Density Kilogramspermetrecubed(kg/m3)
Mass Kilograms (kg)
Volume Metrescubed(m3)
Energyneeded Joules(J)
Specificlatentheat Jouleperkilogram(J/kg)
Changeinthermalenergy Joules(J)
Specificheatcapacity JouleperkilogramdegreesCelsius(J/kg°C)
Temperaturechange DegreesCelsius( °C)
Pressure Pascals (Pa)
∆E=mXc X ∆θ
Kinetictheoryofgases
Gasparticlesareinaconstantstateofrandommotion.
Nokineticenergyislostwhengasparticlescollidewitheachotheror
thecontainer.
Temperatureofgasislinkedtotheaveragekineticenergyofthe
particles.
Ifkineticenergyincreasessodoesthetemperatureofgas.
Pressureofafixedvolumeofgasincreasesastemperatureincreases(temperatureincreases,speedincreases,collisionsoccurmorefrequentlyandwithmoreforceso
pressureincreases).
PV=constant.
Freezing Liquidturnstoasolid.Internalenergydecreases.
Melting Solidturnstoaliquid.Internalenergyincreases.
Boiling/Evaporating
Liquidturnstoagas.Internalenergyincreases.
Condensation Gasturnstoaliquid.Internalenergydecreases.
Sublimation Solidturnsdirectlyintoagas.Internalenergyincreases.
Conservationofmass
Whensubstanceschangestate,massisconserved.
Physicalchange
Nonew substanceismade,processcanbereversed.
SpecificLatentHeat
Energyneededtochange1kgof asubstance’sstate
SpecificLatentHeatofFusion
Energyneededtochange1kgofsolidinto1kgofliquidatthesametemperature
SpecificLatentHeatof
Vaporisation
Energyneededtochange1kgofliquidinto1kgofgasatthesametemperature
Internalene
rgy
Energystoredinsideasystembyparticles
Internalenergyisthetotalkineticandpotentialenergyofalltheparticles(atomsand
molecules)inasystem.
Heatingchangestheenergystored
withinasystem
Heatingcausesachangeinstate.Asparticlesseparate,potentialenergystoredincreases.
Heatingincreasesthetemperatureofasystem.Particlesmovefastersokineticenergyof
particlesincreases.
∆E=mXL
Density Massofasubstanceinagivenvolume
PHYSICS ONLY: whenyoudoworkthetemperatureincreases e.g. pumpairquicklyintoaball,theairgetshotbecauseasthepistoninthepumpmovestheparticlesbounceoffincreasingkineticenergy, whichcausesa temperaturerise.
Reducingthevolumeofafixedmassofgas
increasesthepressure.
Halvingthevolumedoublesthepressure.
SpecificHeat
Capacity
Energyneededtoraise1kgofsubstanceby
1°C
Dependson:• Massofsubstance• Whatthesubstanceis• Energyputintothe
system.
P1V1 =P2V2
better hope – brighter futureAtom
structure
AQAATOMIC
STRUCTURE
Nuclearfissionan
dfusio
n
AtomsandNuclearRadiation
AtomsandIsotopes
PHYSICSONLY:HazardsandusesofRadioactive
emissionsandofbackgroundradiation
Particle Charge Size Found
Neutron None 1Inthenucleus
Proton + 1
Electron - Tiny Orbitsthenucleus
Atom Samenumberofprotonsandelectrons
Ion Unequalnumberofelectronstoprotons
Massnumber Numberofprotonsand neutrons
Atomicnumber Numberofprotons
Negativeion PositiveionElectronsgained Electronslost
Democritus Suggestedideaofatomsas smallspheresthatcannotbecut.
JJThomson(1897)
Discoveredelectrons– emittedfromsurfaceofhotmetal.Showedelectronsarenegativelychargedand
thattheyare muchlessmassivethanatoms.
Thomson(1904)
Proposed‘plumpudding’ model – atomsareaballofpositivechargewithnegativeelectronsembeddedinit.
GeigerandMarsden(1909)
Directedbeamofalpha particles(He2+)atathinsheetofgoldfoil.Foundsometravelledthrough,somewere
deflected,somebouncedback.
Rutherford(1911)
Usedaboveevidencetosuggestalphaparticlesdeflected duetoelectrostaticinteractionbetweentheverysmallchargednucleus,nucleuswasmassive.Proposedmassandpositivechargecontainedinnucleuswhileelectronsfoundoutsidethenucleus
whichcancelthepositivechargeexactly.
Bohr(1913)
Suggestedmodernmodelofatom– electronsincircularorbitsaroundnucleus, electronscanchangeorbitsbyemittingorabsorbingelectromagnetic
radiation.Hisresearchledtotheideaofsomeparticleswithinthenucleushavingpositivecharge;thesewere
namedprotons.
Chadwick(1932)
Discoveredneutronsinnucleus– enablingotherscientiststoaccountformassofatom.
Discoveryofthenucleus
Nuclear
fissio
n One largeunstablenucleussplitstomaketwosmallernuclei
Neutronhits U-235nucleus, nucleusabsorbsneutron,splitsemittingtwoorthreeneutronsandtwosmallernuclei.
Processalsoreleasesenergy.
Processrepeats, chainreactionformed
Usedinnuclear powerstations
Nuclear
fusio
n Twosmallnucleijointomakeonelarger
nucleus
DifficulttodoonEarth– hugeamountsofpressureandtemperature
needed.OccursinstarsPH
YSICSONLY:
Nuclearene
rgy
Fuelrods MadeofU-238,‘enriched’withU-235(3%).Longandthintoallowneutronstoescape, hittingnuclei.
Control rods MadeofBoron.Controlstherateofreaction.Boronabsorbsexcessneutrons.
Concrete Neutronshazardous tohumans– thickconcreateshieldprotectsworkers.
Decay Rangeinair Ionisingpower Penetrationpower
Alpha Fewcm Verystrong Stoppedbypaper
Beta Fewm Medium StoppedbyAluminium
Gamma Great distances Weak Stoppedbythicklead
Radiusofanatom1X10-10m
Radioactivedecay
Unstableatomsrandomlyemitradiationtobecomestable
Detecting UseGeigerMullertube
Unit Becquerel
Ionisation Allradiationionises
Isotope
Differentformsofanelementwiththesamenumberofprotonsbutdifferentnumberofneutrons
𝑈"##$% → 𝑇ℎ + 𝐻𝑒#
-".#$-
𝐶01- → 𝑁 + 𝑒31.
41-
𝑇𝑐-$"" → 𝑇𝑐 + 𝛾-$
""
Contamination Unwanted presenceofradioactiveatoms
Irradiation Personisinexposed toradioactivesource
Sievert Unitmeasuringdoseofradiation
BackgroundConstant lowlevelenvironmentalradiation,e.g.fromnucleartesting,nuclearpower,
waste
Halflife
Thetime takentolosehalfofitsinitialradioactivity
Uses Different isotopeshavedifferenthalflives Shorthalf-livesusedinhighdoses,longhalflivesusedinlowdoses.
Tracers UsedwithinbodyIsotopewithshorthalflife injected,allowedtocirculate andcollectindamagedareas.PETscannerusedtodetectemittingradiation.Mustbebetaorgammaasalphadoesnotpenetratethebody.
Radiationtherapy
Usedtotreat illnessese.g.cancer
Cancercellskilledbygammarays.High doseusedtokillcells.Damagetohealthycellspreventedbyfocussedgammaraygun.
Decay EmittedfromnucleusChangesinmass
numberandatomicnumber
Alpha(α) Heliumnuclei( 𝑯𝒆𝟐𝟒 ) -4 -2
Beta(β) Electron( 𝒆3𝟏𝟎 ) 0 +1
Gamma(γ) Electromagneticwave 0 0
Neutron Neutron -1 0