Labreport物理实验报告英文Word文档下载推荐.docx

Labreport物理实验报告英文Word文档下载推荐.docx

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isthepermittivityofvacuum,

istherelativepermittivity.Permittivityisconstantofproportionalitythatrelatestheelectricfieldinamaterialtotheelectricdisplacementinthatmaterialandrelativepermittivityis 

theratioofthepermittivityofasubstancetothatoffreespaceorvacuum.Differentmaterialshavedifferentrelativepermittivity,thebehindtableincludestherelativepermittivityofsomedifferentmaterial:

Material

Acetaldehyde

AceticAcid

Acetone

Acetone

DielectricConstant 

Source:

（TheEngineeringToolBox,2011.）

Whentwocapacitorsareplacedinseries,thechargeoneachplateisofequalmagnitude,so:

;

hence

（whereQistheamountofchargesonplateandVisthevoltageacrossthecapacitor）.Whenacapacitorischarged（Vacrosscapacitor）:

and

（

istheinitialvoltageaddingonthecapacitor,

isaconstantanditis,Risresistance,Ciscapacitanceand

istheinitialcurrentflowingthroughthecapacitor）.Analogously,whenacapacitorisdischarged,itflows

and

.

Methods

Apparatus:

Powersupply,leads,ruler,calipers,clips,knowncapacitor,aluminumfoil,cling-film,paper,multi-meter,videocamera.

PartA:

usingthreedifferentwaystomeasurethecapacitanceifthegivencapacitor.

Method1ofpartA

Diagram1:

Thismethodismeasuringtheincreasingvoltageofthegivenresistorwhilethecapacitorischarged.Voltageoftheresisterismeasuredbyamulti-meter,whichisatoolthatcanmeasuremanyquantitiessuchasvoltage,current,andresistance.Thegivencapacitorhasanarea（A）of

andthedistance（d）is

.TheVchangesveryfast,sothereneedsaresistertoslowitdownandacameratorecord.Thevoltageofcapacitorcanbefoundbymeasuringthevoltageoftheresister,asvoltageofthecapacitorisequaltotheoutputvoltagesubtractingthevoltageofresistor:

.Whentheloopisconnected,usingthecameratorecordthechangeofvoltage.Afterrecording,drawingagraphoftheV（Vshouldbethevoltageofcapacitoranditisequalto

）andt（thetimeconstant）,thenusingtheequationintheorytofindRCandC.

Table1:

Resultofmethod1ofpartA

t（time）/s

V（voltageofresistor）/v

V（outputvoltage）/v

Analysisforthemethod1

Graph1:

thisgraphisdrawnfromtheresultofmethod1.

Graph2:

thestandardgraph.

V（voltage）

Theinitialvoltage（

）is.

whent=RC,

=,soV=,fromthegraph,t=9swhenV=.Therefore,RCisequalto9,astheresistanceofresistor（R）isgivenandwhichis

.Thecapacitanceofcapacitoris

butheretheresultis

sotheexperimentworksnotwell.Therearesomereasonsresultingtothebigerrorbetweentherealvalueandexperimentvalue.Firstofall,comparingthestandardgraphwiththeresultgraph,Whentimeiszero,thevoltagealsoshouldbezero,however,thevoltageofcapacitorisnotzeroast=0,thisisduetothecapacitorhassomechargesinitbeforetheloopisconnected.Second,asthedataisgottenfromthevideobyeyes,thereexiststhemanmadeerror.Third,thevoltmeteritselfisaresistor,thisalsowillcausetheerror.Inaddition,whentheexperimentisoperated,theloopisnotconnectedverywellandthecapacitorhasbeenused.

Method2ofpartA

Diagram2:

Thismethodismeasuringthecurrentwhilethecapacitorischarging.Thewayofmethod2issameasmethod1andtheresistor,powersupplyandcapacitorarestillthesame.First,usingthecameratorecorddata.Then,drawingagraphaccordingtothesedata.Last,calculatingthecapacitanceaccordingtothegraph.Forthismethod,theformulais

istheinitialcurrentflowingthroughthecapacitor）.

Table2:

Resultofmethod2ofpartA

I（current）/A

Analysisforthemethod2

Graph3:

thisgraphisdrawnfromtheresultofmethod2.

Therelationshipbetweenthecurrentandtimeis

.Whent=RC,

theinitialcurrent（

）is,soI=.Fromthegraph,thetime（t）iswhenI=.Ast=RC,soRC=,

.Comparingtheresultandtherealcapacitance,thismethodworkswell.However,therearestillsomeerrorswhicharecannotbeavoided.Forexample,thedatagottenfromthevideoisnotaccuracy.

Method3ofpartA

Diagram3

Thismethodismeasuringthevoltagewhiledischarging.Similartothemethod1and2,thismethodisalsousingcameratorecordthedataanddrawingagraph,then,usingthegraphandformulatogetthecapacitanceofthecapacitor.

Table3:

Resultofmethod3ofpartA

V（voltageofcapacitor）/v

Analysisforthemethod3

Graph4:

thisgraphisdrawnfromtheresultofmethod3.

Whenacapacitordischarged:

.

=,Whent=RC,

.Fromthegraph,t=3sasV=,SORC=3,

.Therealcapacitanceis

comparingtheresultwiththereal,theresultisnotaccuracy.Therearealsosomeerrorsexist,thefirstisthethereissomecurrentflowingthroughthevoltmeterwhichwasignored.Thesecondiswhenthedatarecordedbyeyes,theremustbesomemanmadeerrors.

PartB:

Makingacapacitor

Thispartisdescribingtheprocessofmakingacapacitorbyusingcling-filmandaluminumfoil.Firstofall,puttingcling-filmonthedeskandspreadingit.Second,layingthealuminumfoilonthecling-filmtidily.Then,puttingthecling-filmabovethealuminumfoilagain.Thenext,lettingthealuminumonthetopandmakesurethetwoaluminumcannottoucheachother.Atlast,rollingthemcarefullyandusingmulti-metertotestwhetherthereiscurrentbetweenthetwoaluminumfoilsforonemeteratime.Afterrolling,thecapacitorwasmade.Thelengthofmaterialsis4meterswithawideofmeters,sothearea（A）is1metersquare.Thedistance（d）betweentwoaluminumfoilsis

whichismeasuredbyacalipers.Ifthecapacitorneedstostoremorecharge,theareashouldbelargerandthedistanceshouldbesmaller.

PartC:

Measuringthecapacitanceofthecapacitormadeinclass.

Method1ofpartC:

Diagram4:

ThispartisgoingtoEstimatethesizeofthecapacitor（capacitance）whichwasmadeinclassbyusingfourmethods.Thismethodismeasuringthecapacitancebyusingaknowncapacitorandlettheminseries.Theformulais

Thevoltageofcapacitor1gottenfromtheexperimentis,theoutputvoltageis20v,so

Theresult

.Inaddition,

Ais

anddis

therefore,

.Thisresultisreasonableandtherearesomeerrorsexist.First,whentheloopisconnected,thecapacitorwillbechargedandthedataonvoltmeterwillchange,soreadingtheinitialdataofthevoltmeter（whichwasusedas

）isnotaccuracy.Second,thepowersupplyhasintervalresistance,sothevoltageofcapacitor1isnotequalto

absolutely.

Method2ofpartC:

Diagram5

Thismethodisusingthesamemethodasmethod1ofpartA.

Table4:

Resultofmethod2ofpartC

Graph5:

=,soV=,fromthegraph,t=whenV=.Therefore,RCisequalto,astheresistanceofresistor（R）isgivenandwhichis

.sotheresultis

.Thisresultisnotgood,whatresultsthebadresultiserrorsofthisexperimentsuchastheintervalresistanceofthevoltmeterandthemanmadeerroronreadingthedatafromvideo.

Method3ofpartC

Diagram6:

Thismethodisalsousingthesamemethodasmethod2ofpartA

Table5:

Resultofmethod3ofpartC

Graph6:

thisgraphisdrawnfromtheresultofmethod3

）is,soI=.Fromthegraph,thetime