P2Topic1&2

Proton

Neutron Electron

Charge

+1 0 -1

Mass 1 1 0.0005 (almost zero)

The charge and mass of electrons, protons and neutrons P2.1Sta)cElectricity

Protons=posi0velychargedElectrons=nega0velycharged.Electronsareintheshellsofatoms.Chargeofanatom=neutralasthe+andthe–areequal.

Sta)celectricityIninsulatorcanbecomechargedbyfric0onthroughthetransferofelectrons.Asubstancethatgainselectronsbecomesnega)velycharged,whileasubstancethatloseselectronsbecomesposi)velycharged.WhenachargedobjectcomesneartoanotherobjecttheywilleitheraIractorrepeleachother.Ifthechargesarethesame-theyrepelIfthechargesareopposite-theya9ract

P2.1Electrosta0cPhenomenaThenega0velychargedballoonrepelstheelectronsinthewallandtheymoveaway.Theposi0vechargeleKbehindaIractstheballoon.

Thenega0velychargedcombrepelstheelectronsinthepaper.Theposi0vechargeleKbehindisaIractedtothecombwhichiswhyitpicksupthepaper.

P2.2UsesandDangersofsta)cHowlightningiscaused:

•  Sta0celectricitycanbuildupinclouds.Thiscancauseahugesparktoformbetweenthegroundandthecloud.

•  Aflowofchargethroughtheatmosphere.Sta0cisdangerouswhen:•  Thereareinflammablegasesorvapoursorahighconcentra0onofoxygen.Aspark

couldignitethegasesandcauseanexplosion.•  Youtouchsomethingwithalargeelectricchargeonit.Thechargewillflowthrough

yourbodycausinganelectricshock.Sta0celectricitybuildsuponeverydayobjects.Itcanbedangerousifitcancreateaspark.Aconduc0ngpathcanbeusedtopreventsparking.

Earthingremovesexcesschargebymovementofelectrons.Theelectronsflowthroughtheearthingcabletoearthratherthantherebeingadischargeandspark.

PaintSpraying1)Thecarisnega0velycharged.2)Thepaintisposi0velycharged.Theposi0velychargedpaintspreadsoutastherepeleachother.3)Thenega0veaIractedtotheposi0veands0ck.4)Themetalspraynozzleisconnectedtotheposi0veterminalofthepowerpackandthepaintpicksupaposi0vecharge.

AircraKcanbuildupasta0cchargewhenflyingthroughtheairandrefuellingcanalsobuildacharge.TostopexplosionstheaircraKhasabondinglinewhichisusedtoconnecttheaircraKtotheearthbeforeithasbeenrefuelled.

Insec)cidespraysInsec0cideusesta0celectricity.SprayedfromaircraKsothattheycoveralargearea.Riskthatsomeofthespraywillblowawayorfallunevenly.Topreventthis,theinsec0cideisgivenasta0cchargeasitleavestheaircraK.Thesta0cdropsspreadevenlyastheyallhavethesamechargeandareaIractedtotheearth.

P2.2UsesandDangersofsta)c

P2.3ElectricCurrentsMaterialscontainelectrons.Insula0ngmaterialstheelectronscannotmovebutinametaltheymoveandthiscanandthiscreatesacurrent.

Beabletousetheequa0on:charge(coulomb,C)=current(ampere,A)x)me(second,s)

Q=Ixt

Keyterms•  Currentistheflowofcharge•  Currentinmetalsistheflowofelectrons•  CellsandbaIeriessupplydirectcurrent

(d.c.)•  Directcurrentisthemovementofchargein

onedirec0on.

Voltmeter Ammeter

MeasuresvoltageinVolts

MeasurescurrentinAmps

Measurestheenergydifferencebetweentheelectronsgoingintothecomponentandback.

Electronsnotusedupouttheoutputisthesameastheinputbacktothecell.

Parallel Series

Nojunc0ons Currentsplitsupatajunc0on

Poten0aldifferencemeasured.

Currentsizemeasured.

P2.4CurrentandVoltage.

Poten0aldifferenceistheenergytransferredperunitcharge.1Voltis1JouleperCoulomb

P2.6Changingresistances•  Resistancemeasureshowharditisfortheelectricitytoflowthrougha

circuit.•  MeasuredinOhms•  Dependantonhowmanycomponentsareinthecircuit.•  Thehighertheresistancethelowerthecurrent.•  Variableresistor=canchangetheresistanceofawire.

Component Resistance

Filamentlamp. Astheygethottheresistancedecreases.Theygethotastheyhaveahigherpoten0aldifference.

Diodes Electricityflowsinonedirec0on.Ifapoten0aldifferenceisappliedintheotherdirectnocurrentwillflow.

Lightdependantresistor Resistanceishighinthedarkandlowintheday0me

Thermistor Highresistancewhencold,lowresistancewhenhot.

Beabletousetheequa0on:poten)aldifference(volt,V)=current(ampere,A)xresistance(ohm,Ω)

V=IxR

P2.6ChangingResistances

P2.7Transferringenergy Equa0onsyoumustbeabletouseCalcula0ngElectricalPower

electricalpower(waI,W)=current(ampere,A)xpoten)aldifference(volt,V)P=IxV

Energytransferred(joule,J)=current(ampere,A)xpoten)aldifference(volt,V)x)me(second,s)E=IxVxt

Dis0nguishbetweentheadvantagesanddisadvantagesofthehea0ngeffectofanelectriccurrent

Advantages Disadvantages

UsefulHea0ngakeIle

Wastedenergy

UsefulinFires Causeburns

Acurrentinawireisaflowofelectrons.Astheelectronsmoveinametaltheycollidewiththeionsinthelagceandtransfersomeenergytothem.Thisiswhyaresistorheatsupwhenacurrentflowsthrough.

P2Topic3

ForceandMo0on

VectorsandVelocityQuan00eswhichhaveadirec0onandsizeareknownasVECTORQUANTITIES.4Examples•  Displacement–distancetravelledinapar0culardirec0on.•  Velocity–speedinapar0culardirec0on.•  Force–alwayshasasizeanddirec0on.•  Accelera0on–ithassizeanddirec0on

Speed(m/s)=distance(m)÷0me(s)

Accelera0on(m/s2)=changeinvelocity(m/s)÷0me(s)

Keyequa0onsyouneedtobeabletouse:

Distance/TimeGraphs•  Horizontallinesmeanthe

objectissta0onary.•  Straightslopinglinesmean

theobjectistravellingataconstantspeed.

•  Thesteepertheslope,thefastertheobjectistravelling.

•  Acurvedlinemeansaccelera0on.

•  Toworkouttheaccelera0on,youneedtocalculatethegradient.

Velocity/TimeGraph•  Horizontallinesmeanthe

objectistravellingataconstantvelocity.

•  Straightslopinglinesmeantheobjectisaccelera0ngordecelera0ng.

•  Thesteepertheslope,thefastertheaccelera0on.

•  Acurvedlinemeansaccelera0on.

•  Theareaunderthegraphisthedistancetravelled.

ForcesAforceisapushorapull.Whentwobodiesinteract,theforcestheyexertoneachotherareequalinsizeandoppositeindirec0on.TheseareknownasREACTIONFORCES.

Youneedtobeabletointerpretthesediagramsandworkouttheresultantforceineachdirec0on.

Iftheresultantforceiszero,itwillremainatrestorcon0nuetotravelataconstantspeed.Iftheresultantforceisnotzero,itwillaccelerateinthedirec0onoftheresultantforce.

ForcesandAccelera0onThesizeofaccelera0ondependson:•  Sizeoftheforce

•  Massoftheobject

Keyequa0onyouneedtobeabletouse:

Force(N)=Mass(kg)xaccelera0on(m/s2)

Inavacuum•  allfallingbodiesaccelerateatthesamerate.

Intheatmosphere•  Airresistanceincreaseswithincreasingspeed.•  Airresistancewillincreaseun0litisequalinsizetotheweightofafalling

object.•  Whenthetwoforcesarebalanced,accelera0oniszeroandTERMINAL

VELOCITYisachieved.

TerminalVelocity

Keyequa0onyouneedtobeabletouse:

Weight(N)=Mass(kg)xgravity(N/kg)

P2Topic3

Momentum,energy,workandpower

StoppingDistancesStoppingdistance=thinkingdistance+breakingdistance

6Factorsaffec0ngstoppingdistance:1.  Massofvehicle2.  Speedofvehicle3.  Driversreac0on0me4.  Stateofthebreaks5.  Stateoftheroad6.  Amountoffric0onbetween

thetyreandtheroadsurface.

5Factorsaffec0ngreac0on0me:1.  Ageofdriver2.  Drugse.g.alcohol3.  Visibility4.  Tiredness5.  Distrac0ons

Inves0ga0ngfric0on.Howmuchforceisneededtomoveweightsondifferentsurfaces?

MomentumAmeasureofmo0on.Massmul0pliedbyvelocity.Whenamovingobjectcollideswithanotherobject,themomentumisthesamebeforethecollisionasitisaKerthecollision.

MomentumandSafetyWhenyouaretravellinginacar(oronabike,skis,trainetc.)youaretravellingatthesamespeedasthecar.Ifthecarstopssuddenly,yourmomentumcon0nuestocarryyouforward.Ifyouarestoppedsuddenly,byhigngthedashboard(orground)youexperiencealargeforce,andthereforealargeamountofdamage.

Carsafetyfeatures:1.  Seatbelts–stretchtoincreasethe0metakentostop,thusreducingtherateof

changeofmomentumandreducinginjury2.  Airbags–inflatetoincreasethe0metakentostop,thusreducingtherateof

changeofmomentumandreducinginjury3.  CrumpleZones–crumpleandfoldinaspecificwaytoincreasethe0metakento

stop,thusreducingtherateofchangeofmomentumandreducinginjury

Usethisformula:Force(N)=changeinmomentum÷0me

Ifyouincreasethe0meyoureducetheforce.

WorkandPowerKeydefini0ons•  Work–theamountofenergytransferred.MeasuredinJoules(J)•  Power–Therateofdoingwork.MeasuredinWaIs(W).1jouleper

secondis1waI.

Usethisformula:WorkDone(J)=Force(N)xdistancemoved(m)Example–ifa1kgmass(10N)ismovedthroughadistanceof2metrestheworkdoneis20J.

Usethisformula:Power(W)=WorkDone(J)÷Timetaken(s)Example–ifa24Jofworkisdoneovera30secondperiod,thePowerwouldbe24÷30=0.8W

Poten0alandKine0cEnergy

Youneedtobeabletousetheseequa0ons:GPE=mghKE=½mv2

KeyDefini0ons•  Kine0cEnergy–movementenergy•  Gravita0onalPoten0alEnergy–theenergysomethinghasduetoitsposi0onrela0ve

toEarth–i.e.itsheight.

Conserva0onofEnergyWhenenergyistransferred,thetotalamountalwaysremainsthesame.

P2

Topic5NuclearFissionandNuclearFusion

P2.23Isotopes

Keywords•  Sub-atomicpar)cles–apar0clethatissmallerthananatom•  Nucleons–Thesubatomicpar0clesinthenucleusofanatome.g.protonsandneutrons•  Isotopes–Atomsofanelementwiththesamenumberofprotonsandelectronsbutwitha

differentnumberofneutrons.

Remember•  TheMassnumberisMorethat

theatomicnumber

Atoms•  Atomscontainelectrons,protonsandneutrons=subatomicpar)cles•  ProtonsandNeutronsinthenucleus=theyarecallednucleons•  Allatomsononeelementhavesamenumberofprotons=atomicnumber•  Massnumber=numberofprotonsandneutronsinthenucleusIsotopes•  Atomswithdifferentnumberofneutron(samenumberofprotons)•  Differentmassnumbers•  Examples

–  Lithium–6andLithium-7–  Carbon-12andCarbon-14

•  AnatomwithanumberaIachedreferredtotheisotope(asabove)

Ionisingradia)on

Keywords•  Unstable–anunstablenucleusisonethatwilldecayandgiveoutionisingradia0on•  Radioac)veDecay–whenanunstablenucleuschangesbygivingoutionisingradia0on

tobecomemorestable•  Ion-Anatomwithanelectricalcharge(throughlossorgainofelectrons)

P2.24Ionisingradia0on

Alpha Beta Gamma

•  Par0clescontaining2protonsand2neutrons(Heliumatomnucleus)

•  Noelectrons=2+charge•  EmiIedfromnucleusathigh

speed•  Loseenergyastheyionisean

atom•  Producemanyionsquicklyso

haveshortpenetra)ondistance

•  Stoppedbyafewcmofairofmmofpaper

•  ElectronsthatareemiIedfromanunstablenucleus

•  Muchlessionisingthatalpha

•  CanpenetratemuchfurtherintomaIer

•  Stoppedbyafewmmoraluminiumoreventhinnerlead.

•  High-frequencyelectromagne)cwavesemmitedbyunstablenuclei

•  Travelatthespeedoflight

•  Ten)meslessionisingthatbeta

•  PenetratemaIereasily•  Stoppedbyafewcmof

leadormanymetresofconcrete.

P2.25Nuclearreac0ons

Keywords•  Nuclearfission–thespligngonalargenucleus.•  Nuclearfusion–thejoiningoftwosmallnuclei

NuclearFission•  Nucleussplitsintotwosmallernuclei•  Twoormoreneutronsalsoreleased•  NOTthesameasradioac0vedecay•  Ifneutronareabsorbedbyothernucleiitcanmakethemunstable–theythen

splitreleasingmorenuclei=chainreac)on(likeanatomicbomb.•  Canbecontrolledwithmaterialstoabsorbneutrons(likeinanuclearreactor)

Radioac)veDecay•  Releasesenergy•  AlphaandBeta=kine)cenergy•  Gamma=energyinformofelectromagne)c

radia)on

NuclearFusion•  Smallnucleicancombineto

formlargerones•  Alsoreleasesalotofenergy

P2.26Nuclearpower

NuclearReactors•  Transformenergycontainedinnucleiofuraniumandplutoniumintothermalenergy•  Nuclearfission•  Pelletsofuraniuminsertedintohollowrods•  Rodsplaceinreactorcore•  Rateiskeptconstantbutcontrollingthechainreac0on•  Numberoffreeneutronswillnotincreaseofdecrease•  Extraneutronsabsorbedbycontrolrods•  Controlrodsplacedinbetweenfuelrodsinreactorcore•  Controlrodscanbemovedinandouttochangetherateoffission•  Fullyloweredtheyshutdownthereactor.

Keywords•  Moderator–asubstancein

anuclearreactorwhichslowsdownneutronssothattheycanbeabsorbedbythenuclearfuelmoreeasily.

•  Radioac)vewaste–MaterialleKoveraKerthefissionofuraniumthatisradioac0ve

Genera)ngelectricity•  Thermalenergyfromcoreistransferredtocoolant

(usuallywater)•  Coolantpumpedthroughreactor•  Coolantathighpressurepumpedtoheatexchangerto

producesteam•  Steamdrivesturbinewhichturnsgenerator•  Generatortransferskine0cenergytoelectricalenergy.

P2.27Fusion–ourfuture?

KeywordsPeerreviewed–workcheckedbydifferentscien0stsworkinginthesamefieldValidate–toconfirmscien0fictheoryistrue

•  Scien0stsinves0ga0ngfusiontogenerateelectricity•  Theheliumproducedisnotradioac)ve•  Materialsusedtocontainfusiondobecomeradioac0veGe_ngnewideasaccepted•  Scien0fictheorieshavetobevalidated•  Bythescien)ficcommunity•  Reportandresultsarepeer-reviewed•  Otherscien0stsmustcarryouttheexperimentandgetthesameresultsFusionandtemperature•  Thenucleithatfusearebothposi)velychargedsorepel=electrosta)crepulsion•  Nucleineedtobeextremelyclose•  Highdensitynucleiaremorelikelytocollidee.g.intheSunthehighgravita0onalfieldcreateshigh

densitynuclei.•  Difficultcondi0ontocreateonearth•  Fusionreactorstrytoproducehighpressuresandhightemperature•  Hightemperatures=morekine)cenergytoovercomerepulsionandcollide.•  Thesecondi0onsrequirealotofenergy(morethanthereactorcanmakesocurrentlynotvery

efficient)

P2

Topic6Benefitsanddrawbacksofusingradioac0vematerials

P2.28Changingideas

HenriBecquerelandMarieCurie•  AccidentaldiscoverywasmadethatUraniumexposedphotographicplates=

discoveryofradioac)vity•  Showedhowradia0oncouldionisegases•  SkinburnsvisiblefromhandlingRadium•  By1920slinksmadewithcancer(MarieCuriediedoflukaemia)•  Largeamountofionisingradia)on=0ssuedamage(radia0onburns)•  Smalleramountsregularly=DNAdamage(muta0ons)•  Somemuta0onsleadtocancer

KeywordsHazards–causesofharmRisk–likelihoodofharmMuta)on–achangeinthebasesequenceofDNA.

Handlingradioac0vesources•  Riskofharmdecreaseswithdistancefromthesource•  Sourcesalwayshandledwithtongs•  Riskreducedbynotpoin)ngsourcesatpeople•  Keepsourcesinleadlinedcontainers

P2.29NuclearWaste

Highlevelwaste•  ThefissionproductsfromUraniumfuelareveryradioac)ve•  Produceslargeamountsofionisingradia)onforabout50

years•  Remainsmoderatelyradioac0veforthousandsofyearsas

intermediatelevelwaste•  Transportedinthickconcreteandsteelcontainers•  Sealedinglasstopreventescape•  Storedincanistersun0litbecomesILW

Intermediatelevelwaste•  Remainsmoderatelyradioac)vefor

thousandsofyears•  Includesthemetalcylindersthatcontained

uraniumfuelwhichbecomeradioac0ve•  Storedinconcreteandsteelcontainers•  Nonedisposedofyet

LowlevelWaste-•  Onlyslightlyradioac0ve•  Remainssofortensofthousandsofyears•  Clothingandcleaningmaterialsfromnuclearpower

sta0ons•  HospitalsalsoasourceofLLWfromradiotherapy

cancertreatments•  Compactedandburiedinspeciallandfill

Advantagesofnuclearpower Disadvantagesofnuclearpower

•  Sta0ondoesnotproduceCO2•  Lessimpactonglobalwarming

•  Makingthefuelrodsrequiresenergy(CO2released)•  Wastehastobestoredfortensofthousandsofyearswithout

leaks•  PeopleperceiveitasunsafeaKertheChernobylaccident

Disposalmethods1.   Firingintospace

–  Riskofitfallingback

2.   Dumpinginbarrelsatsea–  Barrelscancorrode–  Entersfoodchain

3.   Storageunderground–  Needgeologicallystablesite–  Lowearthquakerisk

P2.30Half-life

Radioac)vedecay•  Unstablenucleusundergoesradioac)ve

decaytobecomemorestable•  Ac0vityofasubstanceisthenumberof

nucleardecayspersecond•  Measureinbecquerel(Bq)•  1Bqisonenucleardecayeachsecond•  Radioac0vedecayisarandomprocess

(cannotpredictit)•  Halflife=the0metakenforhalfthe

unstablenucleiinasampleofaradioac0veisotopetodecay.

•  Halflifedoesnotchangeasthesamplegetssmaller

•  AKerdecaying=morestablenucleus•  Morestablenucleus=lowerac)vity•  Halflifefoundbyrecordingac0vityovera

periodof0me.

Geiger-Mullertube•  Usedtomeasureradioac0vity•  Canbeconnectedtoacounterormay

giveaclickwhenradia0ondetected•  Countrate=numberofclicksper

secondorminute

P2.32Backgroundradia0onKeywords•  Backgroundradia)on–ionisingradia0onthatisaroundusallthe0mefromanumberofsources.

Someisnaturallyoccurring.•  Backgroundcount–theaveragenumberofcountsrecordedbyaGMtubeinacertain0mefrom

backgroundradia0on•  Radongas–naturallyoccurringradioac0vegasthatisemiIedfromrocksasaresultofthedecayof

radioac0veuranium

BackgroundRadia)on•  Mainsource=radongas•  Releasedfromdecayinguraniuminrocks•  Diffusesintotheairfromrocksandsoil•  Medicalsources=x-rays;gammarays(scans)andcancertreatments•  Somefoodarenaturallyradioac0ve•  Cosmicrays=highenergychargedpar0clesfromthestars(liketheSun)andsupernovae,

neutronstarsandblackholes.•  ManycosmicraysarestoppedbytheatmospherebutsomereachEarth.

•  Weareconstantlyexposedtoionisingradia)on–fromspaceandnaturallyoccurring=backgroundradia)on

•  Needstobeconsideredwhenmeasuringasource•  Backgroundcountissubtractedfromthesourcecount

P2.33andP2.34Usesofradia0on

TreatmentofCancer•  Radiotherapy=ionisingradia0ontotreat

cancer.•  Gammaraysusedasbeamstotargetandkill

cancercells.

DiagnosisofCancer•  Gammaraysused•  Atracersolu0oninjectedintobodythatcollects

incancers•  Gammacamerausedtodetectrays•  Passthroughthebodysoeasilydetected

Sterilisa)onofequipment•  Tokillmicroorganismssurgical

instrumentsneedtobesterilised•  Heatusuallyusedbutcannotbeused

onsomethingse.g.plas0cs•  TheyareirradiatedwithGammarays

instead.

Irradia)ngfood•  Bacteriawillcausefoodtodecayormakeusill•  Gammarayskillbacteria•  Makesfoodsaferandlongerlas0ng•  Doesnotmakefoodradioac0ve•  FoodslikeFruit,cerealsandshellfishare

irradiated.

SmokeAlarms•  Containsasourceofalphapar)cles•  Thereisanelectricalcircuitwithagap

between2chargedplates.•  Airingapisconstantlyionisedtherefore

constantelectriccurrent.•  Whensmokegetinthealphapar0cles

areabsorbedandstopsthecurrentdrops=alarmsounds

Checkingthickness•  Useadetectortomeasuretherate

Betapassesthroughpaper•  Thinnerpaper=higherbetacount.

Tracersintheenvironment•  Addedtowatertomonitorpollu)onor

leakingpipesunderground•  GMtubefollowsthepipetodetectleaks.