CBSE NCERT Solutions for Class 10 science Chapter 13

CBSENCERTSolutionsforClass10scienceChapter13

Exercises

Q.1. Whichofthefollowingcorrectlydescribesthemagneticfieldnearalongstraightwire?Thefieldconsistsofstraightlinesperpendiculartothewire.Thefieldconsistsofstraightlinesparalleltothewire.Thefieldconsistsofradiallinesoriginatingfromthewire.Thefieldconsistsofconcentriccirclescentredatthewire.

Solution: Magneticfieldlinesduetolongstraightcurrent-carryingwireformconcentriccircleswithcentreatthewire.Wecanusetherighthandthumbruletofindtheshapeanddirectionofmagneticfield.

Q.2. Imaginethatyouaresittinginachamberwithyourbacktoonewall.Anelectronbeam,movinghorizontallyfromthebackwalltowardsthefrontwall,isdeflectedbyastrongmagneticfieldtoyourrightside.Whatisthedirectionofmagneticfield?

Solution: ThedirectionofthemagneticfieldcanbedeterminedbyapplyingFleming’sleft-handrule.

Weknowthatthedirectionofconventionalcurrentistakentobeinadirectionoppositetothatofthedirectionofelectronbeam.So,themiddlefingershouldpointtowardsthewall.Also,thedirectionofforceistowardstheright,sothethumbpointsright-side.Thisgivesthedirectionoffore-fingerasdownwards,orthedirectionofthemagneticfieldisdownwards.

Q.3. Drawalabelleddiagramofanelectricmotor.Explainitsprincipleandworking.Whatisthefunctionofasplitringinanelectricmotor?

Solution: Anelectricmotorisadevicewhichconvertselectricalenergyintomechanicalenergy.

Principle:Itworksontheprinciplethatwhenacurrent-carryingcoilisplacednormallyinamagneticfield,itexperiencesatorquewhichtendstorotateit.

Working:Whencurrentflowsthroughthecoil,armsABandCDexperienceaforce.AccordingtoFleming’sleft-handrule,armABofthecoilexperiencesaforceinthedownwarddirection.Similarly,armCDofthecoilexperiencesaforceintheupwarddirection.Twoequalandoppositeforcesconstituteacouple,andhencethecoilwillrotateinananticlockwisedirection.Whenthecoilreachestheverticalposition,nocurrentflowsinthecoilandnoforceactsonthecoilinthisposition.(Nowcoilrotatesfurther,andsideABismovedontheright,withitscommutatorsegmenttouchingtheright-handbrush,soithasadownwardforceactingit.Similarly,sideCDhasanupwardforceonit.Thus,thecouplealwaysactsinthesamedirection(clockwise)andthecoilspins.Thesplitringsorcommutatorshelptoreversethedirectionofcurrentinthecircuit.

Q.4. Namesomedevicesinwhichelectricmotorsareused.

NCERTScience Chapter13Magneticeffectsofelectriccurrent

PracticemoreonMagneticeffectsofelectriccurrent Page1 www.embibe.com

https://www.embibe.com/

Solution: Fewdevicesinwhichelectricmotorsareusedareelectricfans,electricmixergrinders,washingmachines,waterpumps.Electricmotorconvertselectricalenergyintomechanicalenergy.

Q.5. Acoilofinsulatedcopperwireisconnectedtoagalvanometer.Whatwillhappenifabarmagnetispushedintothecoil?

Solution: Whenabarmagnetispushedintothecoil,magneticfieldthroughthecoilchanges.Henceelectriccurrentisinducedinthecoilmomentarily.Asaresult,galvanometergetsdeflectedmomentarilyinaparticulardirection.

Q.6. Acoilofinsulatedcopperwireisconnectedtoagalvanometer.Whatwillhappenifabarmagnetiswithdrawnfrominsidethecoil?

Solution: Whenabarmagnetiswithdrawnfrominsidethecoilagainmagneticfieldthroughthecoilchanges.Hence,thecurrentisinducedinthecircuitmomentarilyintheoppositedirectionascomparedtothefirstcase.Asaresult,galvanometerdeflectsagainmomentarily,intheoppositedirection.

Q.7. Acoilofinsulatedcopperwireisconnectedtoagalvanometer.Whatwillhappenifabarmagnetisheldstationaryinsidethecoil?

Solution: Whenabarmagnetisheldstationaryinsidethecoil,magneticfieldthroughthecoildoesnotchange.Hence,therewillbenoinducedcurrentinthecoilandnodeflectioninthegalvanometer.

Q.8. TwocircularcoilsAandBareplacedclosedtoeachother.IfthecurrentinthecoilAischanged,willsomecurrentbeinducedinthecoilB?Givereason.

Solution: CurrentinAproducesamagneticfieldaroundit,andifBisclosetoA,partofmagneticfieldpassesthroughB.IfthecurrentinAischanged,magneticfieldthroughBalsochangesandhencecurrentwillbegeneratedincoilBduetoelectromagneticinduction.

Q.9. Statetheruletodeterminethedirectionofamagneticfieldproducedaroundastraightconductorcarryingcurrent.

Solution: Therulethatisusedtodeterminethemagneticfieldproducedaroundastraightconductorisright-handthumbruleorMaxwell’scorkscrewrule.Imaginethatyouareholdingacurrent-carryingstraightconductorinyourrighthandsuchthatthethumbpointstowardsthedirectionofthecurrent.Thenyourfingerswillwraparoundtheconductorinthedirectionofthefieldlinesofthemagneticfield.Thisisknownastheright-handthumbrule.

Q.10. Statetheruletodeterminethedirectionofaforceexperiencedbyacurrent-carryingstraightconductorplacedinamagneticfieldwhichisperpendiculartoit.

Solution: Flemingsleft-handruleisusedtodeterminethedirectionoftheforceonacurrent-carryingstraightconductorplacedinamagneticfield.Accordingtothisrule,stretchthethumb,forefingerandmiddlefingerofyourlefthandsuchthattheyaremutuallyperpendicular.Iftheindexfingerpointsinthedirectionofmagneticfieldandthemiddlefingerinthedirectionofcurrent,thenthethumbwillpointinthedirectionofmotionortheforceactingontheconductor.

Q.11. Statetheruletodeterminethedirectionofacurrentinducedinacoilduetoitsrotationinamagneticfield.




Solution: Fleming’sright-handruleisusedtodeterminethedirectionoftheinducedcurrentinacoilduetoitsrotationinamagneticfield.Itstatestostretchthethumb,theindexfingerandthemiddlefingeroftherighthandinsuchawaythattheyaremutuallyperpendiculartoeachother.Ifthethumbindicatesthedirectionofmotionoftheconductor,theindexfingerindicatesthedirectionofthemagneticfieldthenthemiddlefingerwillindicatethedirectionoftheinducedcurrent.

Q.12. Explaintheunderlyingprincipleandworkingofanelectricgeneratorbydrawingalabelleddiagram.Whatisthefunctionofbrushes?

Solution: Anelectricgeneratorisadeviceusedtoconvertmechanicalenergyintoelectricalenergy.

Principle:Anelectricgeneratorisbasedontheprincipleofelectromagneticinductionaccordingtowhichifaclosedcoilisrotatedaboutanaxisperpendiculartoauniformmagneticfield,aninducedcurrentisproducedwhosedirectionisgovernedbyFleming’sright-handrule.

Construction:Anelectricgeneratorconsistsofarectangularcoilcalledthearmature,fixedmagnet,slipringsandcarbonbrushes.

Working:Whenthearmatureisrotatedintheclockwisedirectioninsidethemagneticfieldproducedbythemagnets,itcutsmagneticlinesofforce.ThischangingfieldproducesinducedcurrentinthecoilwhosedirectionisgivenbyFleming’sright-handrule.WhentheaxleattachedtotwoslipringsisrotatedsuchthatthearmABmovesupandCDdownwards,inducedcurrentstartstoflowfromAtoBandCtoD.Thus,aninducedcurrentflowinthedirectionABCDandintheexternalcircuit,itflowsfromB2toB1.Afterhalfarotation,armCDstartsmovingup,andABmovesdown.Asaresult,thedirectionofinducedcurrentwillbeDCBAandbegintoflowfromB1toB2intheexternalcircuit.Thus,aftereveryhalfrotation,thepolarityofthecurrentintherespectivearmschanges.Suchacurrent,whichchangesthedirectionafterequalintervalsoftime,iscalledanalternatingcurrent.

Functionofcarbonbrushes:CarbonbrushesB1andB2,arepressedagainstslipringstomaintaincontinuouscontactwithrings.Theexternalcircuitisconnectedtothegeneratorthroughbrushes.

Q.13. Whendoesanelectricshortcircuitoccur?




Solution: Inhouseholdelectriccircuits,iftheinsulationofwiresisdamagedorthereisafaultintheappliance,livewireandtheneutralwirecomesintodirectcontactandshortcircuitoccurs.Insuchasituation,resistanceofthecircuitisverylowthencurrentflowsthroughthewireisveryhigh.Thissituationisknownasashortcircuit.Shortcircuitmayoccurwhentoomanyelectricappliancesareconnectedtoasinglesocket,orawhenahigh-powerratedapplianceisconnectedtolowpowercircuit.,thecurrentinthecircuitabruptlyincreases.

Q.14. Whatisthefunctionofanearthwire?Whyisitnecessarytoearthmetallicappliances?

Solution: Thegreencolouredinsulationwireindomesticcircuitsisearthwire.Itisconnectedtoametalplatedeepintheearthnearthehouse.Itisconnectedtometalpartsofelectricappliancesliketheelectricpress,toaster,tablefan,refrigerator,etc.,ifthelivewiregetsdamagedandtouchesthemetalpartthencurrentalsoflowsthroughthemetalpartofappliancewhichmaygiveelectricshockifwetouchit.Theearthwiretakesthiscurrenttotheearthpreventingdamagetoapplianceaswellastheuser.

Q.15. Thephenomenonofelectromagneticinductionistheprocessofchargingabodytheprocessofgeneratingamagneticfieldduetothecurrentpassingthroughacoilproducinginducedcurrentinacoilduetorelativemotionbetweenthemagnetandthecoil

Solution: Thephenomenoninwhichelectriccurrentisinducedinacoilduetorelativemotionbetweenamagnetandthecoiliscalledelectromagneticinduction.Electromagneticinductionisaphenomenoninwhichachangingmagneticfieldacrossaloopofwireresultsinthegenerationofaninducedemf.

theprocessofrotatingacoilofanelectricmotor

Q.16. Thedeviceusedforproducingelectriccurrentiscalledagenerator

Solution: Thedeviceusedforproducingelectriccurrentiscalledanelectricgenerator.Anelectricgeneratorisadevicethatconvertsmechanicalenergyobtainedfromanexternalsourceintoelectricalenergyastheoutput.

galvanometerammetermotor

Q.17. TheessentialdifferencebetweenanACgeneratorandaDCgeneratoristhatACgeneratorhasanelectromagnetwhileaDCgeneratorhasapermanentmagnet.DCgeneratorwillgenerateahighervoltage.ACgeneratorwillgenerateahighervoltage.ACgeneratorhasslipringswhiletheDCgeneratorhasacommutator.

Solution: TheessentialdifferencebetweenanACgeneratorandaDCgeneratoristhattheACgeneratorhasslipringswhiletheDCgeneratorhasacommutator.InDCgenerator,wehavetwosplitringsalsoknownascommutatortopreventthechangeindirectionofthecurrentwhileinAC,wewantthedirectiontobechangedsoweusenormalslipringstotransfercurrentfrominsideofthegeneratortooutsideofthegenerator.

Q.18. Atthetimeofshortcircuit,thecurrentinthecircuitreducessubstantially.doesnotchange.increasesheavily.

Solution: Ashortcircuitisanelectricalcircuitthatallowsacurrenttotravelalonganunintendedpath,oftenwhereessentiallyno(oraverylow)electricalimpedanceisencountered.Atthetimeofshortcircuit,thecurrentinthecircuitincreasesheavily.

varycontinuously.

Q.19. Anelectricmotorconvertsmechanicalenergyintoelectricalenergy.TrueFalse

Solution: Anelectricmotorconvertselectricalenergytomechanicalenergy.Theyoperateusingprinciplesofelectromagnetism,whichshowsthataforceisappliedwhenanelectriccurrentispresentinamagneticfield.Theelectricmotorisanapplicationofthemagneticeffectofelectriccurrent.Theyareusedinwashingmachines,electricfans,toys,etc.

Q.20. Anelectricgeneratorworksontheprincipleofelectromagneticinduction.True

Solution: Whenacoppercoilisrotatedinthemagneticfield,anelectriccurrentisinducedinthecoil.Thisphenomenoniscalledelectromagneticinductionandelectricmotorworksonthisprinciple.

False

Q.21. Thefieldatthecentreofasolenoidcarryingcurrentwillbeparallelstraightlines.True




Solution: Insideasolenoid,magneticfieldlinesareparalleltoitsaxisanduniformlydistributed.Thefieldlinesinsidethesolenoidareintheformofparallelstraightlines.Thisindicatesthatthemagneticfieldisthesameatallpointsinsidethesolenoid.Thatis,thefieldisuniforminsidethesolenoid.

False

Q.22. Awirewithagreeninsulationisusuallythelivewireofanelectricsupply.TrueFalse

Solution: Inthedomesticpowersupply,thewirewithgreeninsulatingcoveriscalledearthwire.Thelivewireisbrownincolourandbringsinthecurrent.

Q.23. Listtwomethodsofproducingmagneticfield.

Solution: Thetwomethodsofproducingmagneticfieldare:

1.Currentcarryingwireproducesamagneticfield.

2.Permanentmagnetsproducemagneticfieldaroundthem.

Q.24. Howdoesasolenoidbehavelikeamagnet?Canyoudeterminethenorthandsouthpolesofacurrent-carryingsolenoidwiththehelpofabarmagnet?Explain.

Solution: Solenoidconsistsofacoilofmanycircularturnsofinsulatedcoppercoilswrappedcloselyintheshapeofacylinder.Whencurrentflowsthroughthecoilsofthesolenoid,themagneticfieldwillbeproducedaroundthecoilsasshowninthefigure.Thesefieldlinesaresimilartomagneticfieldlinesduetopermanentmagnet.Currentcirculatingsolenoidbehavessimilartoabarmagnet.

Wecanidentifynorthorsouthpolesofasolenoidwiththehelpofabarmagnet.Theendofthesolenoidwhichrepelsthesouthpoleofbarmagnetbehavesasthesouthpole.Similarly,theendwhichrepelsthenorthpoleofabarmagnetbehavesasthenorthpole.

Q.25. Whenistheforceexperiencedbyacurrent-carryingconductorplacedinamagneticfieldlargest?

Solution: Theforceactingonthecurrent-carryingconductorismaximumwhenthecurrentintheconductorisperpendiculartothemagneticfielddirection.

Note:

F=BILSinθθ=Anglethatcurrentmakeswiththemagneticfield.




Questions

Q.1. Whydoesacompassneedlegetdeflectedwhenbroughtnearabarmagnet?

Solution: Acompassneedleisasmallbarmagnetandtheendsofthecompassneedlepointapproximatelytowardsnorthandsouthdirections.Hence,whenitisbroughtnearabarmagnet,itsmagneticfieldlinesinteractwiththebarmagnetandthecompassneedlegetsdeflected.

Q.2. Drawmagneticfieldlinesaroundabarmagnet.

Solution:

Thelinesofmagneticfieldfromabarmagnetformclosedlines.Thestrongestexternalmagneticfieldsarenearthepoles.Amagneticnorthpolewillattractthesouthpoleofanothermagnet,andrepelanorthpole.

Q.3. Consideracircularloopofwirelyingintheplaneofthetable.Letthecurrentpassthroughtheloopclockwise.Applytheright-handruletofindoutthedirectionofthemagneticfieldinsideandoutsidetheloop:

Solution:

Consideracircularloopofwireasshowninthefigure.Theendsofthecoilareconnectedtoabatterythroughaswitchandavariableresistance.Whenthecircuitisclosed,thecurrentflowsthroughtheloopandamagneticfieldwillsetuparoundtheloop.ConsiderthepointAintheloop.ApplyingRight-handthumbrule,sincethedirectionofcurrentisintheupwarddirectionthedirectionofthemagneticfieldsetupwillbeinaclockwisedirection.Similarly,atpointBthedirectionofthemagneticfieldwillbeinananti-clockwisedirection.

Q.4. Whichofthefollowingpropertyofaprotoncanchangewhileitmovesfreelyinamagneticfield?(Theremaybemorethanonecorrectanswer.)

massspeedvelocity

Solution: Eachmovingchargedparticleinamagneticfieldexperiencesaforce.Thedirectionofforceexperiencedbyapositivecharge(i.e.,aproton)isgivenbyFleming'slefthandrule.Theforceactingontheprotonwouldchangebothvelocityandmomentum.

momentum

Solution: Eachmovingchargedparticleinamagneticfieldexperiencesaforce.Thedirectionofforceexperiencedbyapositivecharge(i.e.,aproton)isgivenbyFleming'slefthandrule.Theforceactingontheprotonwouldchangebothvelocityandmomentum.

Q.5. StateFleming’sleft-handrule.




Solution: Itstatesthatifwestretchthethumb,forefingerandthemiddlefinger(ofthelefthand)suchthattheyaremutuallyperpendicularandiftheforefingerandthemiddlefingerpointsinthedirectionofmagneticfieldanddirectionofcurrentrespectively,thenthethumbwillbeinthedirectionofmotionortheforceactingontheconductor.

Fleming’sleft-handrule:

Q.6. Explaindifferentwaystoinducecurrentinacoil.

Solution: Thedifferentwaystoinducecurrentinacoilareasfollows:

(i)Movingamagnettowardsacoilsetsupacurrentinthecoilcircuit,

(ii)Ifacoilismovedrapidlybetweenthetwopolesofahorse-shoemagnet,thenanelectriccurrentisinducedinthecoil.

Q.7. Statetheprincipleofanelectricgenerator.

Solution: Agenerator,alsoknownasadynamo,isadeviceusedtoconvertmechanicalenergyintoelectricalenergy.Itworksontheprincipleofelectromagneticinduction.Whenaclosedcoilisrotatedinauniformmagneticfieldwithitsaxisofrotationperpendiculartothedirectionofthemagneticfield,themagneticfieldlinespassingthroughthecoilchangesandthisinducesacurrentintheloop.

Q.8. Nametwosafetymeasurescommonlyusedinelectriccircuitsandappliances.

Solution: Twosafetymeasurementscommonlyusedinelectriccircuitsare:

1.Electricfuse:Electricfuseisconnectedinseriestopreventoverloadingorshort-circuiting.Inthecaseofoverloadingorshort-circuiting,currentinthecircuitbecomesveryhigh.Alargeamountofheatisproducedduetothishighcurrentandfusegetsmeltedfirstatthistemperature.

2.Properearthingpreventsdamageduetoleakageofcurrent.Metalpartsofelectricappliancesaredirectlyconnectedtoanearthwire.Ifthelivewirecomesincontactwiththemetalpart,currentflowsthroughtheearthwiretotheearthandpreventsdamagetotheapplianceaswellastheuser.

Q.9. Listthepropertiesofmagneticfieldlines.

Solution: 1.Magneticfieldlinesareparalleltoeachotherintheuniformmagneticfield.

2.Magneticfieldlinesdonotcrosseachother.

3.Magneticfieldlinesalwaysformaclosedloop.

4.Outsidethemagnet,magneticfieldlinesaredirectedfromtheNorthPoletotheSouthPoleofthemagnet,whereasinsidethemagnettheyaredirectedfromtheSouthPoletotheNorthPoleofthemagnet.

5.Therelativestrengthofthemagneticfieldisdepictedbythedegreeofclosenessofthefieldlines.Fieldlinesaremorecrowdedataplacewherethefieldisstronger.

Q.10. Themagneticfieldinagivenregionisuniform.Drawadiagramtorepresentit.




Solution: Theuniformmagneticfieldlinesarerepresentedbyparallelequidistantlines.

Themagneticfieldisschematicallypresentedinthediagrambymagneticlinesofforcewhicharecalledasthelinesofmagneticinduction.Arrowsinthediagramshowthedirectionofmagneticlines.Thelinesofinductionarecollectivelycalledtheflux.ItisassumedthatthelineofinductionemergedfromtheNorthPoleandterminatedattheSouthPoleoutsidethemagnet.

Q.11. TakeasmallaluminiumrodAB(ofabout5cm).Usingtwoconnectingwiressuspendithorizontallyfromastand,asshowninFig.Placeastronghorse-shoemagnetinsuchawaythattherodliesbetweenthetwopoleswiththemagneticfielddirectedupwards.Forthisputthenorthpoleofthemagnetverticallybelowandsouthpoleverticallyabovethealuminiumrod.Connectthealuminiumrodinserieswithabattery,akey,andarheostat.NowpassacurrentthroughthealuminiumrodfromendBtoendA.Whatdoyouobserve?Itisobservedthattherodisdisplacedtowardstheleft.Youwillnoticethattherodgetsdisplaced.Reversethedirectionofcurrentflowingthroughtherodandobservethedirectionofitsdisplacement.Itisnowtowardstheright.Whydoestherodgetdisplaced?

Inaboveactivity,howdowethinkthedisplacementofrodABwillbeaffectedif(i)currentinrodABisincreased;(ii)astrongerhorse-shoemagnetisusedand(iii)lengthoftherodABisincreased?

Solution: (i)Ifthecurrentintherodisincreased,theforceexertedonthecurrent-carryingrodincreasesandhence,thedisplacementoftherodincreases.

(ii)Ifastronghorse-shoemagnetisused,magneticfieldstrengthincreasesandhenceforceonthecurrent-carryingrodalsoincreases.Thisincreasesthedisplacementoftherod.

(iii)Ifthelengthoftherodisincreased,theforceontherodincreases.Displacementoftheroddependsonthemassoftherodaswell.Therefore,dataisinsufficienttojudge.

Q.12. Whatistheprincipleofanelectricmotor?

Solution: Theelectricmotorworksontheprincipleofthemagneticeffectofcurrent.Whenacurrent-carryingconductorisplacedinamagneticfield,itexperiencesmagneticforceonit.ThedirectionoftheforcecanbefoundusingFleming’sleft-handrule.Note:Anelectricmotorisarotatingdevicethatconvertselectricalenergyintomechanicalenergy.Whenarectangularcoilisplacedinamagneticfieldandcurrentispassedthroughit,aforceactsonthecoilwhichrotatesitcontinuously.

Q.13. Namesomesourcesofdirectcurrent.




Solution: Someofthesourcesofdirectcurrentaredrycells,buttoncellsandleadaccumulator.Note:Directcurrentisanelectriccurrentflowinginonedirectiononly.

Q.14. Anelectricovenof2kWpowerratingisoperatedinadomesticelectriccircuit(220V)thathasacurrentratingof5A.Whatresultdoyouexpect?Explain.

Solution: Poweroftheoven,P=2kW=2000WPotentialdifferenceapplied,V=220VPowerconsumedcanbewrittenas,P=V×I⇒I=PV=2000W220V=9.09A

Thisexceedsthesafelimitvalueofthedomesticcircuit,i.e. 5A.Thus,electricfuseinthecircuitwillmeltandbreaksthecircuit.

Q.15. Whydon’ttwomagneticlinesofforceintersecteachother?

Solution: Thetwomagneticfieldlinesdonotintersecteachotherbecauseatthepointofintersectiontherewillbetwodirectionsofmagneticfieldbecauseoftwotangentlinesatapoint,whichisnotpossible.

Q.16. Themagneticfieldinsidealongstraightsolenoid-carryingcurrentiszero.decreasesaswemovetowardsitsend.increasesaswemovetowardsitsend.isthesameatallpoints.

Solution: Themagneticfieldinsidealongstraightsolenoidcarrying-currentisthesameatallpoints.Themagneticfieldinsidealongstraightsolenoid-carryingcurrentisthesameatallpoints.Itisbecausethemagneticfieldinthesolenoidisconstantbecausethelinesarecompletelyparalleltoeachother.

Q.17. Apositively-chargedparticle(alpha-particle)projectedtowardsthewestisdeflectedtowardsthenorthbyamagneticfield.Thedirectionofthemagneticfieldis

towardsthesouthtowardstheeastdownwardupward

Solution: Herealphaparticleismovingtowardsthewest,sothedirectionofcurrentistowardsthewest.Thedeflectionistowardsthenorth,sotheforceistowardsthenorth.Itstatesthatifwestretchthethumbthedirectionofthemagneticfieldisupward.

Q.18. Whatistheroleofthesplitringinanelectricmotor?

Solution: Asplitringactsjustlikeacommutatorintheelectricmotor.Acommutatorisadevicethatreversesthedirectionofflowofcurrentthroughacircuit.Thereversingofthiscurrentalsoreversesthedirectionofforceactingonthetwoarms.Note:Thereversingofcurrentisnecessaryfortherotationoftherectangularcoilinthesamedirection.

Q.19. Whichsourcesproducealternatingcurrent?

Solution: Thesourcesarehydroelectricpowerplants,thermalpowergenerators,nuclearpowergenerators,ACgeneratorsproducealternatingcurrent.

Note:Alternatingcurrentisthecurrentthatperiodicallyreversesitsdirection.

Q.20. Whatprecautionshouldbetakentoavoidtheoverloadingofdomesticelectriccircuits?

Solution: Followingprecautionsshouldbetakentoavoidtheoverloadingofdomesticcircuits:

1. Theelectricfusemustbeconnectedinserieswiththecircuittopreventoverloadingorshort-circuiting.2. Donotusetoomanyhigh-powerapplianceslikeair-conditioner,electricmotor,waterheater,

etc.simultaneously.3. Donotconnecttoomanyappliancestoasinglesocket.4. Usetheappliancewithinthesafelimitoftheelectriccircuit.

Q.21. Arectangularcoilofcopperwiresisrotatedinamagneticfield.Thedirectionoftheinducedcurrentchangesonceineachtworevolutionsonerevolutionhalfrevolution




Solution: Whenarectangularcoilofcopperwiresisrotatedinamagneticfield,thedirectionoftheinducedcurrentchangesonceineachhalfrevolution.Note:Splitringusedintheelectricmotorisalsocalledasacommutator.Acommutatorisusedtoreversethedirectionofcurrentinthecoilofmotor.Thefunctionofcommutatorringsistoreversethedirectionofcurrentflowingthroughthecoileverytimethecoiljustpassestheverticalpositionduringarevolution.Inotherwords,commutatorringsreversethedirectionofcurrentflowingthroughthecoilaftereveryhalfrotationofthecoil.

one-fourthrevolution







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CBSE NCERT Solutions for Class 10 science Chapter 13

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