初三物理知识点总结

初三物理知识点总结

Physicalquantity(unit)formula;deformationofremarkformula

SpeedV(m/S)v=S:distance/t:time

GravityG(N)G=mgM:massg:9.8N/kgor10N/kg

Thedensityof=m/Vm(kg/m3)P:quality:VolumeV

TheresultantforceisthesameasF(N):Fand=F1+F2

Intheoppositedirection:whenFistheoppositeof=F1-F2,F1>F2

BuoyancyFfloat

(N)F,floating=Gmatter-G,dependingontheG:thegravityoftheobjectintheliquid

BuoyancyFfloat

(N)Ffloating=Gmatter,thisformulaappliesonly

Objectfloatingorsuspended

BuoyancyFfloat

(N)F=G=mg=Pfloatingrowrowrowrowrow:GgVliquidliquidgravity

PlatoonM:thequalityoftheliquid

P:liquidliquiddensity

PlatoonV:thevolumeoftheliquid

(thatis,thevolumeimmersedinaliquid)

LeverbalanceconditionsF1L1=,F2L2,F1:powerL1:powerarm

F2:resistanceL2:resistancearm

FixedpulleyF=G

S=hF:thepullofthefreeendoftherope

G:gravityofobjects

S:thedistanceatwhichtheendoftheropemoves

H:thedistancethatanobjectrises

MovingpulleyF=(Gobject+Gwheel)

S=2,h,Gobjects:thegravityofobjects

Gwheel:thegravityofthemovingpulley

PulleyblockF=(G,+Gwheel)

S=nHN:thenumberofsegmentsoftheropebymovingthepulley

MechanicalworkW

(J)W=FsF:force

S:thedistancetraveledinthedirectionofforce

Usefulwork,W,yes

TotalWtotalW=GH

Wtotal=Fsappliespulleyblockvertically

Mechanicalefficiency=x100%

PowerP

(W)P=

W:work!

T:time

PressureP

(Pa)P=

F:stress

S:forcearea

LiquidpressureP

(Pa)P=PGHP:liquiddensity

H:depth(fromliquidleveltodesiredpoint)

Verticaldistance

Unitformulaofphysicalquantity

Name,symbol,name,symbol

Thequalityismkgkgm=pv

ThetemperatureistdegreesCelsius,CdegreesCelsius

Speedvm/sec,m/sv=s/t

Densitypkg/M3kg/m3p=m/v

Force(gravity)FNewton(cow)NG=mg

ThepressureisPPascal(PA)PaP=F/S

WorkWJoule(focus)JW=Fs

PowerPwatt(W)wP=W/t

CurrentIampere(an)AI=U/R

VoltageUvolts(volts)VU=IR

ResistanceRohm(OU)R=U/I

ElectricalworkWJoule(focus)JW=UIt

ElectricalpowerPwatts(Watts)wP=W/t=UI

HeatQJoule(coke)JQ=cm(T-Tdegrees)

SpecificheatCJiao/(kgdegreeC)J/(kgdegreesC)

Inthevacuum,thespeedoflightis3*108meterspersecond

G9.8Newton/kg

15degreesCairspeedof340meterspersecond

[heatpart]

1,heatabsorption:Qabsorption=Cm(T-t0)=Cm,deltaT

2heatrelease:Q=Cm(t0-t)=Cm=t

3,calorificvalue:q=Q/m

4,theefficiencyoffurnaceandheatengine:ETA=Qtheeffectiveuseof/Qfuel

5,heatbalanceequation:Q=Qsuction

6,thermodynamictemperature:T=T273K

[electricalpart]

1,currentstrength:I=Q,electricity/t

2,resistance:R=PL/S

3Ohm'sLaw:I=U/R

4Joule'slaw:

(1)Q=I2Rtuniversalformula)

(2)Q=UIt=Pt=UQelectric=U2t/R(pureresistanceformula)

5、seriescircuit:

(1)I=I1=I2

(2),U=U1U2

(3),R=R1R2

(4)U1/U2=R1/R2(partialpressureformula)

(5)P1/P2=R1/R2

6、parallelcircuit:

(1),I=I1I2

(2)U=U1=U2

(3),1/R=1/R11/R2[R=R1R2/(R1R2)]

(4)I1/I2=R2/R1(shuntformula)

(5)P1/P2=R2/R1

7fixedresistance:

(1)I1/I2=U1/U2

(2)P1/P2=I12/I22

(3)P1/P2=U12/U22

8electricwork:

(1)W=UIt=Pt=UQ(universalformula)

(2)W=I2Rt=U2t/R(pureresistanceformula)

9electricpower:

(1)P=W/t=UI(universalformula)

(2)P=I2R=U2/R(pureresistanceformula)

AllphysicsformulasunderGradeEight

V/V/Pliquiddischarge=P(Ffloat=G)

V/V=P-Pliquiddewrowmaterial/P

V/V=Pexposed-P/Pliquidliquid

V=V,G/F=P/Pliquidfloating

Aphysicaltheorem,law,formula

I.themotionofaparticle(1)--rectilinearmotion

1)uniformvariablelinearmotion

1.averagespeed=V=s/t(definition)2.usefulinferencesVt2-Vo2=2As

3.intermediatetime,speedVt/2=V,flat=(Vt+Vo)/24.,endvelocityVt=Vo+at

5.intermediatepositionspeedVs/2=[(Vo2+Vt2)/2]1/26.displacementS=Vflatt=Vot+at2/2=Vt/2t

7.accelerationa(Vt-Vo)/t={VoisaandVotothesamedirection,a>0(acceleration);reversea<0}

The8.corollaryiss=aT2{Deltasforcontinuoustime(T)adjacentequaldisplacementdifference}

9.mainphysicalquantitiesandunits:initialvelocity(Vo):m/s;acceleration(a):m/s2;terminalvelocity(Vt):m/s;time(T)seconds(s);displacement(s):m(m);distance:m;speed

unitconverted:1m/s=3.6km/h.

Note:

(1)theaveragespeedisavector;

(2)theobjectisverylargeandtheaccelerationisnotnecessarilylarge;

(3)a=(Vt-Vo)/tisjustameasure,notadecision;

(4)otherrelevantcontent:particle,displacementanddistance,referencesystem,timeandtime(seebook1,P19),/s--tdiagram,v--tdiagram/speedandrate,instantaneousvelocity[seebook1,P24].

2)freefallmotion

1.initialvelocity=Vo2,velocityVt=GT

3.dropheighth=gt2/2(downfromVoposition)4.inferenceVt2=2GH

Note:

(1)freefallmotionisauniformlyacceleratedlinearmotionwithzeroinitialvelocity,andfollowsthelawofuniformandvariablerectilinearmotion;

(2)a=g=9.8m/s2=10m/s2(theaccelerationofgravityattheequatorissmallerinthemountainsthanplains,vertical

direction).

(3)verticalprojectilemotion

1.s=2.Vot-gt2/2displacementspeedVt=Vo-gt(g=9.8m/s2=10m/s2)

3.usefulinferencesVt2-Vo2=-2gs4.risemaximumheightHm=Vo2/2g(throwpointscount)

5.round-triptimet=2Vo/g(timefromthrowingbacktooriginalposition)

Note:

(1)thewholeprocessisauniformdecelerationlinearmotion,inwhichtheupwarddirectionispositive,andtheaccelerationisnegative;

I.measurement

ThelengthofL:mainunits:meters;measurementscale;measurementtools:whenestimatingtheminimumscalereadnext;lightunitisaunitoflength.

Thetimeinseconds;t:themainmeasurementtools:watchwithstopwatchinthelaboratory.1=3600seconds,onesecond=1000milliseconds.

3M:substancescontainedinthenumberofobjectscalledquality.Mainunit:kg;measuringtools:scales;laboratory

trays;balances.

Two.Mechanicalmovement

Themechanicalmovement:theobjectpositionchangesofmovement.

Reference:tojudgethemotionofanobject,anotherobjectmustbechosenasthestandard.Thisobjectischosenasastandard.Itiscalledareference.

Theuniformlinearmotion:

Comparethetwomethodsofmovingspeed:acomparesthedistancetraveledinequaltime.Bcomparesthetimerequiredtotravelbyequaldistance.

Formula:1meterspersecond=3.6km/h.

Three,force

TheFforce:forceistheobjectroleofobjects.Theforcesactingbetweenbodiesarealwaysreciprocal.

Aunitofforce:Newton(N).Aninstrumentformeasuringforce:adynamometer;alaboratoryusesaspringbalance.

Theactofmakinganobjectdeformorchangethestateofanobject.

Achangeinthestateofanobjectisachangeinthespeedor

directionofanobject.

Thethreeelementsofthethreeelements:forcesize,directionandfunctioniscalledforce.

Theforcediagramshouldbescaled;theschematicdiagramofforceisnotscaled.

3G:gravityduetotheearthtobringtheobjectsbyforce.Direction:verticaldownward.

Gravityandmassrelations:G=mg,m=G/g

G=9.8cow/kg.Reading:9.8cowsperkilogram,whichmeans1kgofbodyweightand9.8kgofgravity.

Centerofgravity:thepointofgravityiscalledthecenterofgravityofanobject.Thecenterofgravityofaregularobjectatthegeometriccenterofanobject.

Thetwo:theequilibriumconditionsoftheforceactonthesameobject;twoforceequalandoppositedirection;inastraightline.

Anobjectcanbestationaryattwoforcesandcanmoveatuniformspeed.

Theequilibriumstateofanobjectisastateinwhichtheobjectisinastationaryoruniformlinearmotion.Theresultantforceofanobjectinequilibriumiszero.

Thesynthesisofthesamelineoftwoforces:thesamedirectionofresultantforcedirectionF=F1+F2;andF1,F2thesamedirection;

Theoppositedirection:forceF=F1-F2,thedirectionoftheresultantforceisthesameasthatofthelargeforce.

Thesameconditions,therollingfrictionforceofslidingfrictionforceismuchsmallerthan.

Slidingfrictionisrelatedtopositivepressure,contactsurface,materialproperties,androughness.[slidingfriction,rollingfriction,staticfriction]

7.Newton'sfirstlaw,alsoknownasthelawofinertia,thecontentis:allobjectsintheabsenceofexternalforce,alwaysmaintainastaticoruniformlinearmotionstate.Inertia:thepropertyofanobjecthavingthestateofbeingstationaryoruniforminalinearmotion,calledinertia.

Fourdensity

Thedensityofasubstance:thequalityofunitvolume,densityisapropertyofmatter.

Formula:m=PVinternationalunit:kg/M3g/cm3commonunits,

Relationship:1g/cm3=1*103kg/m3;

WaterP=1x103kg/m3;

Reading:103kilogramspercubicmeter,representing1cubicmetersofwater,thequalityof103kilograms.

Thedensitymeasurement:measuringqualityofpalletscales,solidorliquidvolumemeasuringcylinder.

Unitofareaconversion:

1cm2=1*10-4m2,

1mm2=1*10-6m2.

Five,pressure

ThepressureP:objectunitareapressureiscalledpressure.

PressureF:theforceactingverticallyonthesurfaceofanobject(N).

Theeffectofpressureisexpressedbypressure,whichisrelatedtothesizeofthepressureandtheareaoftheforce.

Pressureunit:cattle/M2;specialname:Pascal(Pa)

Formula:F=PS[S:theforcearea,thecommonpartoftwoobjectscontact;unit:m2.]

Themethodofchangingthepressureis:reducingpressureorincreasingtheforceareacanreducethepressure;secondly,increasingthepressureorreducingtheforceareacanincrease

thepressure.

Theliquidinternalpressure:[internalpressuremeasuringliquid:liquidpressuregauge(Utubemanometer).]

Causes:astheliquidhasgravity,itproducespressureonthebottomofthecontainer;pressureisappliedtothewallofthevesselbecauseofitsliquidflow.

Law:atthesamedepth,thepressureisequalinalldirections;thegreaterthedepth,thegreaterthepressure;atthesamedepthoftheliquid,thedensityoftheliquidislargeandthepressureisgreat.[depthhtheverticalheightoftheliquidtoapointoftheliquid.]

Formula:P=PGHH:unit:m;P:kg/M3g=9.8/kgofcattle.

Atmosphericpressure,atmosphericpressurecausedbygravity,atmosphericpressurethatexistsandisagreatMagdeburghemispheresexperiment,determinationofatmosphericpressurevaluesisToriandLi(Italyscientists).WhentheToritubeistilted,themercurycolumnstaysthesameandthelengthbecomeslonger.

1standardatmosphericpressure=76cm,mercurycolumn=1.01*105PA=10.336m,watercolumnhigh

Aninstrumentformeasuringatmosphericpressure:Barometer(mercurybarometer,cassettebarometer).

Atmosphericpressurevarieswithaltitude:thehigherthe

altitude,thelowerthepressure,whichdecreaseswithincreasingaltitudeandtheboilingpointdecreases.

Six,buoyancy

1.buoyancyandcauses:objectsimmersedinliquids(orgases)aresubjectedtoliquids(orgases),andtheirbuoyancyiscalledbuoyancy.Direction:verticalupward;cause:liquidtoupperandlowerpressuredifferenceofanobject.

2.Archimedesprinciple:theobjectimmersedinaliquidisupwardbuoyancy,thesizeofthebuoyancyisequaltothegravityoftheliquid.

F=G=PfloatingliquiddischargeliquidgV.(Vrowsindicatethesizeoftheliquidintheobject)

Formula3.:F=G-T=floatbuoyancyP=F,liquidgVunderpressure

When4.objectsfloat:F=GandPfloatingmatterP<liquidwhentheobjectsuspended:F=GandsubstancePfloatingliquid=P

Whentheobjectsurface:F>GandP<floatingsubstancePsolutionwhentheobjectsinks:F<GandP>floatingsubstancePsolution

Seven,simplemachinery

Theleverbalancecondition:F1l1=F2l2.Forcearm:the

verticaldistancefromthefulcrumtotheforceactingontheline

Theaimoftheleverinthewaterpositionistoadjustthelengthofthepowerarmandtheresistancearmbyadjustingthenutatbothendsofthelever.

Fixedpulley:equivalenttoequalarmlever,cannotsaveeffort,butcanchangethedirectionofforce.

Movingblock:equivalenttothepowerarmis2timestheresistancearmlever,cansavehalfoftheforce,butcannotchangethedirectionofforce.

Thepower:twoessentialfactors:theroleoftheforceontheobject;theobjectinthedirectionoftheforcebythedistance.W=FSworkunit:Joule

3.power:theworkdonebyanobjectinunittime.Aphysicalquantityindicatingthespeedatwhichanobjectdoesitswork,i.e.,alargepowerobjectcandoworkquickly.

TheunitofW=PtP:Watt;unitofW:Joule;tunit:sec.

Eight,heat:

Thetemperatureoftsaid:thedegreeofhotandcoldobjects.[isastatequantity.]

Commonthermometerprinciple:accordingtoliquidexpansionandcontractionproperties.

Thedifferencebetweenthermometerandthermometeris:range,minimumscale,glassbulbandbenttubule,andmethodofuse.

Theheattransferconditions:temperaturedifference.Heat:theamountofheatabsorbedorreleasedbyanobjectduringheattransfer.[processquantity]

Heattransfermode:conduction(heattransferalongtheobject),convection(byliquidorgasflowtoachieveheattransfer)andradiation(hightemperatureobjectsdirectlyoutoftheheat)threekinds.

3:vaporizationphenomenonfromliquidintoagaseoussubstance.Way:evaporationandboiling,vaporizationtoheatabsorption.

Factorsinfluencingevaporationrateare:liquidtemperature,liquidsurfaceareaandliquidsurfaceairflow.Evaporationhasacoolingeffect.

ThespecificheatcapacityofC:amaterialunitmass,temperatureriseof1degreesCelsiuswhentheheatabsorbedbytheheatcapacityofthismaterialiscalled.

Specificheatisoneofthepropertiesofasubstance.Theunithasthelargestspecificheatofthewaterinthecommonsubstance.

Cwater=4.2*103Jiao/(kgC)reading:4.2*103joulesperkilogramcelsius.

Physicalmeaning:themassis1kilograms,thewatertemperatureisincreasedby1degrees,andtheabsorbedheatis4.2*103jiao.

Thecalculationofheat:Q=cmQ=cmtdropdeltadeltaT+absorption

QandC,m,deltaTisproportionaltoC,m,deltaTisinverselyproportionalto.Deltat=Q/cm

6.internalenergy:thesumofkineticenergyandmolecularpotentialenergyofallmoleculesinanobject.Allbodieshaveinternalenergy.Internalenergyunit:Joule

Theinternalenergyofanobjectisrelatedtothetemperatureoftheobject.Whenthebodytemperatureincreases,theinternalenergyincreases;thetemperaturedecreasesandtheinternalenergydecreases.

Themethodofchangingtheinternalenergyofanobject:doingworkandheattransfer(whichisequivalenttochangingtheinternalenergyofanobject)

7.thelawofconservationandTransformation:energythatdoesnotcomeoutofnowhere,willnotdisappear,itwillonlybetransformedfromoneformintootherforms,ortransferredfromonebodytoanother,andtheamountofenergyremainsunchanged.

Nine,circuit

Thecircuitiscomposedofpowersupply,switch,electrical

appliances,wiresandothercomponents.Tokeepcurrentinthecircuit,thecircuitmusthaveapowersupplyandthecircuitshouldbeclosed.Thecircuithascircuit,breakcircuit(opencircuit),shortcircuitofpowersupplyandelectricappliance.

Theeasyconductivesubstancecalledconductor.Anaqueoussolutionofmetals,acids,bases,salts.Asubstancethatisnotconductiveiscalledaninsulator.Suchaswood,glass,etc..

Insulatorscanbeconvertedintoconductorsundercertainconditions.

Identificationof3seriesandparallelcircuits:Series:currentbifurcation,

(3)FMisslightlygreaterthanFN,generallyregardedasFM=FN;

(4)otherrelevantcontent:staticfriction(size,direction)[seevolume1P8];

(5)physicalquantities,symbolsandunitsB:magneticinductionintensity(T),L:effectivelength(m),I:currentintensity(A),V:chargedparticlevelocity(m/s),q:chargedparticles(chargedbody),electricity(C);

(6)thedirectionofAmpereforceandLorentzforcearedeterminedbythelefthandrule.

2)thesynthesisanddecompositionofforces

1.thesynthesisofforcesonthesamelineisthesamedirection:F=F1+F2,reverse:F=F1-F2(F1>F2)

2.synthesisofangularforce:

F=(F12+F22+2F1F2cos)1/2(F1groupF2cosinetheorem):F=(F12+F22)1/2

3.forcesizerange:|F1-F2|=F=|F1+F2|

Theorthogonaldecompositionof4.forces:Fx=Fcosbeta,Fy=Fsinbeta(betaistheanglebetweentheresultantforceandtheXaxis,TG,beta=Fy/Fx)

Note:

(1)thesynthesisanddecompositionofforce(vector)followstheparallelogramrule;

(2)therelationbetweentheresultantforceandthecomponentforceistheequivalentsubstitutionrelation,whichcanbeusedasasubstituteforthecomponentforce,andviceversa;

(3)inadditiontoformulamethod,itcanalsobesolvedbygraphmethod.Atthistime,thescaleshouldbechosenandplottedstrictly;

(4)whenthevalueofF1andF2isconstant,thegreatertheangle(alphaangle)ofF1andF2,thesmallertheresultantforce;

(5)thesynthesisofforcesonthesamelinecantakethepositivedirectionalongthestraightline,andthedirectionofforceisrepresentedbypositiveandnegativenumbers,andisreducedtoalgebraicoperations.

Four,dynamics(movementandforce)

1.Newton'sfirstlawofmotion(Lawofinertia):anobjecthasinertia,andalwaysmaintainsauniform,linear,orstationarystateuntilanexternalforceforcesittochangeit

2.Newtonsecondlawofmotion:F==maora=F,/ma{,determinedbyexternalforces,inaccordancewiththedirectionoftheexternalforce}

3.Newton'sthirdlawofmotion:F=-F'{signintheoppositedirection,F,F'eachroleineachother,thepracticalapplicationofbalanceforceandforcecounterforcedifference:recoilmovement}

4.concurrentforcebalanceF=0,{generalizedorthogonaldecompositionmethod,threeintersectionprinciple}

5.overweight:FN>G,weightloss:FN<G{accelerationdirectiondown,allweightloss,accelerationdirectionupward,alloverweight}

6.theapplicableconditionsofNewton'slawsofmotion:suitableforsolvinglow-speedmotionproblems,applicabletomacroobjects,notapplicabletodealingwithhigh-speed

problems,notapplicabletomicroscopicparticles[seebook1P67]

Note:theequilibriumstatemeansthattheobjectisinastationaryoruniformlinearstate,orthatitrotatesatuniformspeed.

Fivevibrationandwave(mechanicalvibrationandmechanicalvibrationtransmission)

F=-kx{F:1.harmonicvibrationrestoringforce,theproportionofk:coefficient,x:displacement,FdirectionandXsignalwaysreverse}

2.cycleT=2pi{l:(l/g)1/2(m),thelengthofthependulumg:localgravityaccelerationvalue,theestablishmentofconditions:theswingangletheta<100;l>>r}

3.forcedvibrationfrequencycharacteristics:F=fdrivingforce

4.resonanceconditionsoccur:Fdrivingforce=fsolid,A=max,resonancepreventionandapplication[seevolume1P175]

5.mechanicalwave,transversewaveandlongitudinalwave[seevolumesecondP2]

6.wavevelocityv=s/t=lambdaf=lambda/T{wavepropagationacyclepropagatesonewavelengthforwardthewavevelocityisdeterminedbythemediumitself}

7.soundwavevelocity(inair)0DEGC:332m/s;

20DEGC:344m/s;30DEGC:349m/s;(acousticwaveislongitudinalwave)

Asharpdiffractionof8.waves(wavestravelaroundobstaclesorholes):conditionsofobstructionsorholesaresmallerthanorsmallerthanthewavelength

9.waveinterferenceconditions:twowavefrequency(constantamplitude,thesameissimilar,thesamevibrationdirection)

10.Dopplereffect:becauseofthemutualmovementbetweensourceandobserver,LEDsourceemissionfrequencyandreceivefrequencydifferent{mutuallyclose,receivingfrequencyincreases,conversely,decreases,seesecondcopiesofP21}

3.thetheoryofmoleculardynamicsisthatmatteriscomposedofalargenumberofmolecules;alargenumberofmoleculesundergoirregularthermalmotions;thereisinteractionbetweenmolecules.

Thegravitationalattractionandrepulsionbetween4.molecules(1)r<r0,fleads<frepulsion,andFmolecularforceexhibitsrepulsiveforce

(2)r=R0,f=f,F,molecularforce=0,Emolecularpotential=Emin(minimum)

(3)r>r0,fleadsto>frepulsion,andtheFmolecularforceexhibitsattraction

(4)r>10r0,f=f=0Fmolecularforcespending,about0,about0Emolecularpotential

5.thefirstlawofthermodynamicsW+Q=Delta{U(powerandheattransfer,thetwoobjectscanchangethewaythatisequivalentineffecton),

PositiveworkisdoneonabodyoutsideW:(J),Q:(J)absorbsheat,canincreasetheU:(J),relatedtothefirstkindcannotcreate,seesecondcopiesofP40}

Nine,thenatureofgas

1.stateparameterofgas:

Temperature:thedegreeoftemperatureofanobjectonthemacroscopiclevel;themicroscopicsignoftheextentoftheirregularmovementofmoleculesintheobject,

TherelationshipbetweentemperatureandCelsiustemperature:T=t+273{T:(K),t:temperatureinCelsius(c)}

VolumeV:thespaceoccupiedbyagasmolecule.Theunitisconvertedto1m3=103L=106mL

PressureP:intheunitarea,alargenumberofgasmoleculesfrequentlyimpingingonthewallofthereactorproducecontinuousanduniformpressure.Thestandardatmosphericpressureis1atm=1.013*105Pa=76cmHg(1Pa=1N/m2)

2.gasmolecularmovementcharacteristics:largespacebetweenmolecules;inadditiontothemomentofcollision,theinteractionisweak;molecularmotionrateisverylarge

Thestateequationofidealgas3.:p1V1/T1=p2V2/T2PV/T={T}isconstant,thermodynamictemperature

1,electricalwork:theworkdonebyelectricityiscalledelectricalwork.Theprocessofdoingworkbyelectricityistheprocessofconvertingelectricenergyintootherformsofenergy.

Formula:W=UIt=Pt=t=I2Rt=UQ(whereW=t=I2Rt,appliedonlytopureresistancecircuit)

Unit:Joule(J),commonlyusedunitkilowatthour(KWh)1KWh=3.6*106J

Measurement:anelectricmeter(formeasuringtheamountofelectricalenergyconsumedbyanelectricapplianceinahomecircuit)

Connection:theseriesinthehomecircuitintheroad"1,3"into"2,4";"1,2"fire"3,4"zero

Parameters:220V10A(20A)"saidthemetershouldbeusedin220Vcircuits;ratedcurrentmeterfor10A,inashortperiodoftimecannotexceedthecurrent20A;circuitwithtotalpowercannotexceed2200Wappliances;"50Hz"saidmetershouldbeusedinthefrequencyofthealternatingcurrentcircuit50Hz;"3000R/KWh"saideveryworkingcircuitconsumes1KWhpowermeter

dial3000rpmrotation.

Calculationformulaofelectricpowerindirectlymeasuredbyelectricenergymeter:P=*3.

6*106(W)

2.Electricpower:electricpoweristheworkdonebyelectriccurrentinunittime.Equaltotheproductofcurrentandvoltage.Theunitofelectricpoweriswatt.Formula:P=W/t=UI==I2R(whereP==I2Ronlyappliestopurelyresistivecircuits)

3.Thedifferenceandrelationbetweenratedpowerandactualpower:theratedpowerisdeterminedbytheelectricequipmentitself,andtheactualpowerisdeterminedbytheactualcircuit.Contact:P==(2P),canbeunderstoodthatwhenthevoltageatbothendsoftheapplianceischangedtotheoriginal1/n,thepowerbecomes1/n2oftheoriginalpower.

4thelightandshadeofasmallbulbisdeterminedbytheactualpowerofthebulb.

5,Joule'sLaw:thecurrentgeneratedbytheconductorofheatQisproportionaltothesqu