NaturalScienceYear6–Unit8:Electricityandmagnetism

ElectricityandmagnetismElectricityandmagnetismaretwodifferentphenomenathatarepresentinnature.Electricityistheflowofchargedparticles,andmagnetismistheforceofattractionorrepulsionbetweenobjects.Inthepast,scientistswereawareofelectricityandmagnetism.However,itwasnotuntilthe19thcenturythattheyrealisedtherewasacloserelationshipbetweenthesetwothings.Theyalsodiscoveredthatitwaspossibletocreateamagneticfieldusinganelectricalcurrent.Theinteractionoftheseforcesiscalledelectromagnetism.Whatareelectromagnets?

Whatiselectricity?Electricityisanessentialpartofourdailylives.Weuseelectricityforalmosteverythingwedo,whetherit'sturningonthelightsinourhouse,playingourfavouritevideogame,orevenblowdryingourhair.Didyoueverstoptothinkaboutwherethiselectricitycomesfromorhowdoesitwork?Tounderstandthis,weneedtoknowaboutatomsandtheirstructure.

ElectricalchargesElectricityisaformofenergy.Electricitybeginswiththesmallestofallparticles,theatom.Atoms,althoughtoosmallforoureyestosee,areineverything.Atomsalsocontainprotonsandneutronsintheirnucleus(thecentreoftheatom).Electronsarecontainedaroundtheprotonsandneutrons,andmovequicklyaroundthem.Thisquickmovementiswhatmakestheenergyinelectricity.Ifanobjecthasthesamenumberofprotonsandelectrons,itiselectricallyneutral.However,sometimes,electronsmoveeasilyfromoneobjecttoanotherandthismakestheobjectelectricallycharged.

1. Bothobjectsareelectricallyneutral.

2. Werubthepenagainstthecloth.

3. Thepenispositivelychargedandtheclothisnegativelycharged.

ForcesbetweenelectricalchargesElectricallychargedobjectattractorrepeleachother,dependingontheircharges.

NaturalScienceYear6–Unit8:Electricityandmagnetism

Asthehairispositivelychargedandtheballoonnegativelycharged,bothobjectsattract.Asbothballoonsarenegativelycharged,theyrepeleachother.

TypesofelectricityStaticelectricityElectricitycancomeinmanydifferentforms.Forinstance,thinkoftheelectricitythatisproducedwhensomeonereceivesashock,orwhenlaundrygetsstucktogether...thisisstaticelectricity,andisthesametypeofelectricitythatcauseslightningwhenthereisathunderstorm.CurrentelectricityThetypeofenergythatweuseinourhomes,schools,andbusinessesisdifferentthanstaticelectricity.Thistypeofelectricityiscalledcurrentelectricity.Currentelectricityisastreamofelectronsflowingthroughaconductor.Thewaywegettheelectricityinourhomesisfromcurrentelectricity.Powerplantsuseelectromagnetsinsidecopperwire(aconductor)toproducetheelectricitythatissentthroughwirestoourhomes,schools,andbusinesses.ElectricalconductorsandinsulatorsMaterialscanbeclassifieddependingonhowwelltheyconductelectricity.Somematerials,suchasrubberorplastic,aremoreresistanttothemovementofelectrons.Theyarecalledinsulators.Othermaterials,likecopperorsilver,haveverylooselyheldelectronssothismakesthemexcellentconductors.

MaterialsElectricalconductors ElectricalinsulatorsWater,copper,silver Rubber,plastic,wood,glass,porcelain

AnelectricalcircuitElectricalcurrentcanbeproducedandtransportedinaclosedelectricalcircuit.Anelectricalcircuithasthefollowingparts:

• Apowersource(forexample,abattery):itprovidesenergy.

• Wires:theyconductelectricity.• Aswitch:itopensandclosesthecircuit.• Aresistor(forexample,alightbulb):itchanges

electricitytodifferentformsofenergy.

NaturalScienceYear6–Unit8:Electricityandmagnetism

MagnetismAmagnetisanobjectwhichcanattractcertaintypesofmetal,suchasiron.Theabilitytoattractmagneticmaterialsiscalledmagnetism.MagnetsMagnetscanbenaturalorman-made.Themineralmagnetiteisanaturalmagnet,butmostofthemagnetsweusetodayareman-made.Mineralssuchasiron,nickel,andcobaltaremagneticmaterials.Typesofmagnets

• Permanentmagnetsneverlosetheirmagnetism.• Inducedmagnets(ortemporarymagnets)haveatemporary

magneticforce.Forexample,ifyoupickupapaperclipwithamagnet,thepaperclipwillbecometemporarymagnetised.Whenyouremovethemagnet,thepaperclipwillloseitsmagneticforce.

PolesAllmagnetshavetwopoles,northandsouth.Ifyoubreakamagnetinhalf,bothpartswillhaveanorthpoleandsouthpole.Ifyoususpendamagnet,inwaterforexample,italwayspointstotheEarth’smagneticnorthpole.

Ifyouplacetwomagnetswiththeoppositepolestogether,theywillattracteachother.

Ifyouplacetwomagnetswiththesamepolestogether,theywillrepeleachother.

MagneticfieldTheareaaroundamagnetwhereitexertsitsforceiscalledamagneticfield.Wecan’tseethisfield,butwecanseeitsshapeusingironfilings–smallpiecesofironthatlooklikedust.Theironfilingslineupandspreadoutfromthepoles.Themagneticfieldisstrongestatthepoles.

TheEarthisamagnetTheEarth’smoltenironcoreactslikeahugemagnet.ThemagneticNorthPoleisataslightangleawayfromthegeographicalNorthPole,anditisherethatmagnetsincompassespoint.ThemagneticfieldaroundtheEarthdeflects(orchangesthedirectionof)cosmicraysandprotectsouratmosphere.

Didyouknow?TheEarth’smagneticfieldprotectsourplanetfromcosmicrays.However,someofthementertheEarth’satmosphereatthemagneticpoles.Theycombinewiththegasesintheatmospheretoproduceincrediblelighteffects.ThesearecalledtheAuroraBorealisintheNorthernHemisphereandtheAuroraAustralisintheSouthernHemisphere.

NaturalScienceYear6–Unit8:Electricityandmagnetism

CompassAcompassisanavigationalinstrument.TheneedleinthecompassismagnetisedandpointstothemagneticNorthPole.Thecirclearoundtheneedle,alsocalledarose,ismarkedwiththecardinalpoints,north,south,east,andwest,andthedegreesinbetween.Usingamapandacompass,youcanfindyourwayinunknownterrain,evenifvisibilityispoor.Compasseswerefirstusedinmedievaltimesandtheinventionofthedrycompasswhichcouldbetakenaboardshipsmeantthattradeandexplorationflourishedinthisperiod.

MagnetsandelectromagnetsMagneticmaterialsMagneticmaterialsarealwaysmetallic,butnotallmetalsareattractedtomagnets.Lookattheseobjects.Whichdoyouthinkaremagnetic?Carryoutasimpleexperimenttofindout.

ElectromagnetsElectromagnetsareobjectsthatactlikemagnetswhenanelectricalcurrentpassesthroughthem.Thedifferencewithpermanentmagnetsisthatthemagnetisactivatedbyelectricity;ifyouswitchofftheelectricalcurrent,themagnetstopsworking.Electromagnetscanbemadestrongerbyaddingmorecoilsofwireandincreasingtheelectricalcurrent.

Wrapthewire(aconductor)aroundthenail.

Attachtheendsofthewiretothebattery(apowersource).

Placethepaperclipsneartheendofthenail.Observewhathappenstothepaperclipswhenthecircuitisconnectedanddisconnected.

NaturalScienceYear6–Unit8:Electricityandmagnetism

MagnetsallaroundusWeusemagnetseveryday,whetheritistoholdalistontotherefrigeratordoor,ortolistentomusicthroughheadphones,ortopaywithacreditcard.Electromagnetsareusedinmotors,generators,electricbells,loudspeakersandintheharddisksofacomputer.Manyhomeappliances,suchashairdryers,blendersorwashingmachines,usemotorstoconvertelectricityintomechanicalenergy.Inhospitals,magneticresonanceimaging(orMRI)isusedtodetectproblemsinourorgans.Ituseselectromagnetstoo.Magnetsarealsousedformagneticseparationandforliftingheavymetalobjectssuchasscrapandheavymetalpartsforconstruction.Intransport,Maglevtrainsusemagneticlevitationtomovewithouttouchingtheground.Theyareinuseinmanycountries,suchasCanada,Germany,SouthKoreaandJapan.

ElectricitysafetytipsUsingelectricalappliancessafelyWorkingwithelectricityispartofeverydaylife.Eachtimeweswitchonthelights,oruseamobilephone,orpluginanappliance,weinteractwithelectricalequipment.However,electricitycanharmustoo,andinextremecases,anelectricshockcanevenkillus.So,itisimportanttotakecarewhenusingelectricity.

Threethingsyoushouldalwaysdo• Ifyouhaveproblemswiththeelectricalcircuitsinyour

home,callaqualifiedelectrician;faultycircuitscanleadtoelectricalfireswhicharethemaincauseoffiresinhomes.

• Unplugappliancesbeforeworkingonthem;ifanapplianceisconnectedtothemaincircuit,theresultingelectricshockcouldkillyou.

• Knowwhereyourfuseboxandcircuitbreakersaresoyoucanturnoffthemainelectricitysupplyinanemergency.

Threethingsyoushouldneverdo• Neveroverloadsocketsandextensionleads;theycan

overheatandcauseafire.• Neveruseelectricalapplianceswhicharewet;wateris

agreatconductorofelectricityandyoucouldgetashock.

• Neverputanythingintotheholesofasocket,youcouldgetanelectricshock.

Whatisanelectricshock?Anelectricshockhappenswhenapersontouchesanelectricalenergysource.Electricalcurrentflowingthroughapartofthebodywillcauseashock.Whatiselectrocution?Electrocutionisdeathcausedbyelectricshock.Whattodo?Nevertouchthepersonreceivingtheelectricshockuntiltheelectricityisswitchedoffandyouaresureitissafetodoso.Danger:Ifyoutouchthem,youcouldgetanelectricshockorbeelectrocutedyourself.Shoutforagrownuptohelp.