ENGR 1181 | Lab 3: Circuits ‐ Preparation Material ‐ Lab Procedure ‐ Report Guidelines ENGR 1181 Lab 3: Circuits Preparation Material Preparation Material 2
ENGR 1181 Lab 3: Circuits Preparation Material Goal of the Circuits: TheCircuitsLabintroducesseriesandparallelcircuitwhichareusedbyengineers.Studentswill
reviewthisdocumentandthentaketheCarmenquizbeforearrivingatlab.
Learning Objectives IntheCircuitsLab,youwill:
1.
2.
3.
4.
5.
Constructelectriccircuitsusingabreadboard
Developtechniquestomeasurevoltage,currentandresistance
ApplyOhm’sLaw,PowerLaw,Kirchhoff’sCurrentLawandKirchhoff’sVoltageLaw
Calculatetheequivalentresistanceofelectriccircuit
Demonstratethepropercircuitconfigurationforagivenscenario
1. Circuits in Technology Electricalcircuitsareusuallylaidoutonprinted
circuitboards.Theboardismadeofan
electrically‐insulatingmaterial.Muchofthe
"wiring"onaprintedcircuitboardismadefrom
insulatedmetalpathsprintedontheboard,
ratherthanactualwires.Thatiswhytheyare
called"printed"circuitboards.
Figure1showsthefrontandbackoftheprinted
circuitboardinsideaniPodTouch.
Combinationsofresistors,capacitors,diodes,
integratedcircuitsareconnectedbyelectrical
pathsontheboards.Thepinsonthe
componentsareconnectedtogetherbywire
tracesontheboard.
Figure 1: The iPod Touch circuit board
2. Measuring Electrical Circuits Current Electricalcurrentistheflowofelectricchargeviaelectrons.Similartowaterflowingthrougha
pipe.Theamountofwaterflowingthroughapipecanbemeasuredingallonsperminute.Electrical
currentisdefinedastheamountofchargethatmovespastalocationinthewireperunittime(1
ampere=1coulombpersecond).
3
ENGR 1181 Lab 3: Circuits Preparation Material Voltage Voltage(ElectricalPotential)isameasureoftheelectricalforcebetweentwopointswhichcauses
currenttoflow.Justaspressurecauseswatertoflowthroughapipe,avoltagedifferencecauses
electronstoflowthroughawire.Voltageisalwaysmeasuredrelativetoareferencepointinvolts
(V).
Figure2showsadigitalvoltmeterbeingusedtomeasurethevoltagedifference(5.23Volts)across
a1000Ohmresistor.Inthiscase,thevoltageandcurrentthroughtheresistorareconstant,
thereforewecallthisadirectcurrent(DC)circuit.
Figure 2: Measuring voltage across a resistor Resistance Resistanceistheoppositiontotheflowofcurrentthroughaconductor.Aresistorisoneofthe
manyexamplesofanelectroniccomponentthatresiststheflowofcurrent.WhenavoltageV(in
Volts)isappliedacrossaresistor,itcausesthecurrentI(Amperes)toflowthroughtheresistor,
andwecancalculateresistanceRusingOhm'sLaw:
∙ .TheunitofresistanceistheOhm
andissometimesgiventheGreeklettersymbolΩ:
Resistance
R
Ω
(1)
4
ENGR 1181 Lab 3: Circuits Preparation Material Light Emitting Diode (LED) AnLEDisadevicethatemitslightwhencurrentflowsthroughit.Itcanbeusedasalightsource,or
asanindicator.Whatmakesituniquefromothercomponentsisthatcurrentcanonlyflowthrough
itinthedirectionofthearrow.Therefore,anLEDisapolarizedcomponentandmustalwaysbe
insertedintoacircuitboardwiththecorrectorientation.
WhenyoubuildaLEDcircuitinlab,youplugtheLEDintoacircuitboardwiththepositivewire
connectedtothepositivesideofthebattery.Figure3showstwodifferenttypesofLEDs.Inthislab
youwillbeusingtheLEDontheleftduetoitsdurabilityhoweverinfuturelabsyouwillusethe
typeofLEDontherightofFigure3.Itisimportantforfuturereferencethatthelongerwiredenotes
thepositiveleadandsotheshorterlead(negative)goestoground.Figure4isanexampleofanLED
inaschematic.
Figure 3: Two types of LEDs Figure 4: LED schematic symbol Electrical Circuit Schematics Aschematicisanengineeringdrawingofanelectricalcircuit.Each
symbolontheschematicrepresentsacomponentinthecircuit.
Figure5showsthesymbolsforvariouselectricalcomponents.
Thelinesintheschematicrepresentthewiresormetalpathsonthe
circuitboardthatconnectthecomponentstogether.Metalslike
copperandaluminum,whichhaveverylowresistance,areusedfor
circuitconnectionsbecausetheyaregoodconductorsofelectricity.
Figure 5: Schematic symbols 5
ENGR 1181 Lab 3: Circuits Preparation Material 3. Electric Circuit Laws Ohm’s Law Electricalcurrentistheflowofelectricchargeviaelectrons.Similartowaterflowingthrougha
pipe.Theamountofwaterflowingthroughapipecanbemeasuredingallonsperminute.Electrical
currentisdefinedastheamountofchargethatmovespastalocationinthewireperunittime(1
ampere=1coulombpersecond).
ThevoltagedifferenceV(Volts)acrossaresistorisequaltotheproductofthecurrentI(Amperes)
andtheresistanceR(Ohms):
Ohm’sLaw
∗ ∗
(2)
Power Law ThepowerdissipatedP(Watts)inacomponentwithresistanceRisequaltoproductofthevoltage
V(Volts)acrossthecomponentandthecurrentI(Amperes)flowingthroughit:
PowerLaw
UsingOhm’sLaw,
∗
∗ (3a)
PowerLaw
∗ ∗
(3b)
Calculation of current, voltage and power UsetheOhm’sLawtosolvesampleproblems:
Considertheresistorschematic(Figure6)thathasaresistorR=10kΩandavoltageinputV=10
volts.
Calculate:thecurrentflowingthroughtheresistor.
Current, I
I
Ω
,
Ω
0.001Amp
1mA
Figure 6: Resistor schematic
R Voltage, V
6
ENGR 1181 Lab 3: Circuits Preparation Material Forthecaseofthesameresistor,R=10kΩbutwithcurrentof0.5mAflowingthrough,
Calculate:Voltageacrosstheresistor
V
I ∗ R
0.5mA ∗ 10kΩ V
5Volts
0.0005A ∗ 10,000Ω UseOhm’sLawandthePowerLawtosolveasampleproblem.ThecircuitinFigure7hasabattery
voltageV=15VoltsandaresistorR=5Ohms.
Calculate:Currentgoingthroughtheresistor.
UsingOhm’sLaw,
Current, I
I
3Amps
15 Volts
BATTERY
R = 5 Ohms
Calculate:Powerdissipatedintheresistor.
UsingPowerLaw,
P
Figure 7: Basic Circuit Schematic V ∗ I
15V ∗ 3A
45Watts
Kirchhoff’s Voltage Law InthecircuitofFigure8,thebatterycreatesanelectronsflow
throughthewiresandeachresistorinaloop.Electronscarry
negativechargeandleavethenegativeterminal of the battery,
returning to the positive terminal. However, conventional current
is defined as the movement of positive charge, so we define the
positive flow of current as the direction shown of the arrow for I.
Current, I
V1
R1
Vbat
V2
R2
V3
R3
Since the same current I flows through each of the resistors, it
creates the voltage differences across each resistor, shown by the
three voltages V1, V2 and V3. Therefore, the battery voltage Vbat is
equal to the sum of the voltage difference:
Kirchhoff’sVoltageLaw
Figure 8: Kirchhoff's Voltage Law 4
7
ENGR 1181 Lab 3: Circuits Preparation Material Kirchhoff’s Current Law Sincevoltageisthesameacrosseveryresistorconnectedinparallel,thesumofcurrentsentering
intoanodeisequaltothesumofcurrentsleavinganode.Anodeinacircuitisthejunctionof3or
morewire,usuallypresentedasadotsimilarlytoFigure9.
Kirchhoff'sCurrentLaw
(5)
I2
I0
I1
Vbat
R1
R2
Figure 9: Kirchhoff's current law sample circuit
Equivalent Resistance For calculation purposes, several resistors can be replaced by a single “equivalent” resistor (Req).
Resistors Connected in Series Sincethecurrentisthesamethroughalltheresistorsconnectedinseries,thentheequivalence
resistanceisthesumofalltheresistors.Figure10isanexampleofhowanequivalentresistance
canbefoundforresistersinseries.
EquivalentResistance series
(6a)
Current, I
Current, I
V1
R1
Vbat
Vbat
Req (Series)
V2
R2
V3
R3
Figure 10: Equivalence of resistors in series 8
ENGR 1181 Lab 3: Circuits Preparation Material Resistors Connected in Parallel Sincevoltageisthesameacrosseveryresistorconnectedinparallel,thetotalcurrentisthesumof
thecurrentsflowingthroughtheindividualresistors.Figure11isanexampleofhowanequivalent
resistancecanbefoundforresistersinparallel.
1
R
EquivalentResistance parallel 1
R1
1
R2
1
R3
6b
I0
I0
Vbat
R1
R2
Vbat
R3
I1
I2
Req (Parallel)
I3
Figure 11: Equivalent resistance of resistors in parallel Notethattheequivalentresistanceis1/Req,soinordertofindReq,theinversemustbetaken.
Calculation of current power dissipated and equivalent resistance Letusconsideranelectriccircuitschematic(showninFigure12)thathasabatteryvoltageof
VBAT=15VoltsconnectedtoresistorsR1=100ohmsandR2=200ohmsinparallel.
Calculate:CurrentacrossresistorR1,powerdissipated(PR1)acrossresistorR1,andequivalent
resistanceReqofthecircuit.
I2
I0
Vbat
15 Volts
R1
100 Ohms
I1
R2
200 Ohms
Figure 12: Basic circuit with resistors connected in parallel 9
ENGR 1181 Lab 3: Circuits Preparation Material Calculate:CurrentgoingthroughR KeepinmindthatinaparallelcircuitthebatteryvoltageacrossR1andR2isthesame
(VBAT=15volts).Therefore,usingOhm’sLawforresistorR1
I
0.15Amp 150mA
Calculate:PowerdissipatedinR usingthePowerLaw
P V ∗ I
15 ∗ 0.15
2.25Watts
Calculate:R forthecircuit.(Hint:SubstituteR1andR2intoEquation6b)
1
R1
1
R
R
1
R2
1
0.015
1
100Ω
1
200Ω
0.015
66.7Ω
Resistances in Parallel and Series Together Whencalculatingequivalentresistance(Req)inacircuit,astepbystepapproachisbest.First,you
mustidentifyeachuniquegroupinthecircuit.Withineachsub‐groupyoushoulddothefollowing:
1. Foreachresistor,identifywhethertheresistorisinseriesorparallel.
2. Ifinparallel,thencalculateRequsingtheparallelmethod.OtherwisecalculateReq
usingtheseriesmethod.
3. Repeatuntilthesub‐groupisreducedtoasingleReq
4. Proceedtothenextsub‐groupusingstepsuntilthetotalReqiscalculated.
SeetheexampleshowninFigure13.Abatteryisconnectedto3resistors(R1,R2andR3).Resistors
R2andR3areconnectedinseriesandR1isconnectedparalleltoresistorsR2andR3.
10
ENGR 1181 Lab 3: Circuits Preparation Material I2
I0
R2
Vbat
R1
I1
R3
Figure 13: A series and parallel resistances circuit I2
I0
I1
Vbat
R1
R23
Figure 14: A series and parallel resistances circuit converted to only parallel resistances circuit I0
Vbat
Req
Figure 15: Simplified circuit with equivalent resistance. Inordertosolvetheoverallequivalenceresistance,weneedtosimplifythecircuitstepbystep.The
firststepwillbetocombineR2andR3tocreateFigure14.InordertoobtainR23,wewillusethe
equivalenceresistanceequation6aforresistorsR2andR3connectedinseries,orR23=R2+R3.Then
wehaveR1andR23inparallelandwecanuseequation6btoobtaintheequivalentresistanceReqto
simplifythecircuitasshowninFigure15.Thefollowingequation6cshowsthecalculationofthe
totalequivalentresistanceoftheseries‐parallelcircuit,
1
R
EquivalentResistance
1
R
1
R
R
1
R
1
R
6c
11
ENGR 1181 Lab 3: Circuits Preparation Material 4. Equipment Breadboard Breadboardsareusedtoquicklybuildandtestprototypeelectroniccircuits.Circuitcomponents
areinsertedintothesmallcontactholesontopoftheboardtomakeelectricalconnectionstoother
components.Figure17belowshowshowgroupsofholesareconnectedtogether(byshinymetal
stripsrunningverticallyandhorizontallyunderneaththeholesontheboard),allowingcircuit
connectionsonthetopsideoftheboardtobemadeeasily.Atthetopleft,thefirsttwoplastic
connectorsarewired(left‐to‐right):1.toGround(Blackconnector),2.to+5Volts(Redconnector).
ThenexttworedconnectorswillbeusedtoconnectTestProbestotheDigitalMultimeter(DMM).
Figure 16: The front of a breadboard showing the connections between the different alignments of holes Figure 17: The back of a breadboard showing the metal connections correlating to the alignment on the front work surface
Digital Multimeter (DMM) DigitalMultimeter(Figure18)aredesignedtomeasureelectricalproperties.Theyaremost
commonlyusedformeasuringvoltage,current,andresistance.Typically,theleadsonthe
Multimeterarecolor‐coded:redisforPositivepolarityandblackisNegative.Thereareseveral
settingsontheMultimeterthatallowittobeversatile.IntheCircuitsLab,wewillonlyusetheDC
VoltssettingandtheOhmssetting.TheDCVsettingstandsfordirectcurrentvoltage,whichwillbe
usedtomeasurethevoltagedifferencebetweentwopoints.TheΩ(Ohm)settingwillbeusedto
measureelectricalresistance.
Note:theDMMwillnotbeusedtomeasureCURRENT.Currentwillbe
calculatedwithOhm'sLawfrommeasuredvoltageandresistancevalues.
12
ENGR 1181 Lab 3: Circuits Preparation Material DC Voltage (Volts)
Resistance (Ohms)
Figure 18: Digital Multimeter (DMM) with probes attached 5. Further preparation assignment InordertofinishyourpreparationforCircuitsLab,studentsarerequiredto:



WatchthevideoonhowtousetheDMM
TaketheCircuitsLabquizonCarmen
CompletethePre‐LabWorksheetbelow
13
ENGR 1181 Lab 3: Circuits Preparation Material Lab 3: Circuits Lab ‐ Pre‐lab Assignment Name________________________________
Team______
SeatNo._______
Thisisanindividualassignment.
SolvethefiveproblemsbelowandhanditinatthebeginningoftheCircuitsLab.
Problem 1. Ohm’s Law Forthecircuitbelow,calculatethevalueoftheresistorRwhichwouldcausethecurrentof2.5mA
toflowinthecircuit.Whatvoltagewouldyoumeasureacrosstheresistor?Showyourcalculations.
(4points)
I
2.5 mA
R=_________________________
15 Volts
Vbat
R
Vres
Vres=________________________
Problem 2. Kirchhoff’s Voltage Law Forthecircuitbelow,calculate:(1)theequivalentresistance,(2)thecurrent,I,flowinginthe
circuit,(3)thevoltagesV1andV2,and(4)verifythatV1+V2=Vbat.Showallcalculations.(Note:1
kΩ=103Ω).(5points)
I
Req =_____________________
R1
10k
V1
I=_______________________
V1=______________________
5 Volts
Vbat
R2
20k
V2
V2=______________________
V1+V2=_________________=Vbat?
14
ENGR 1181 Lab 3: Circuits Preparation Material Name_____________________________________________
Team___________
SeatNo._______________
Problem 3. Power Law ForthecircuitinProblem2,calculatethepowerdissipatedineachresistor,andthetotalpower
generated.Showallcalculations.(3points)
P1=_______________________P2=_______________________PTotal=_______________________
Problem 4. Equivalent Resistance Calculatethetotalequivalentresistanceofthecircuitbelow.Also,calculatethetotalcurrent
suppliedbythebattery,I0.Showallcalculations.(3points)
I0
6 Volts
Vbat
R1
3 Ohms
I1
R2
9 Ohms
I2
R3
18 Ohms
I3
Req =______________________
I0=________________________
Problem 5. Kirchhoff’s Current Law ForthecircuitinProblem4,calculatethe
currents,I1,I2,andI3.DoesI1+I2+I3=I0
(fromProblem4)?Showallcalculations.(3
points)
I1 =_______________________
I2=_______________________
I3=_______________________
DoesI1+I2+I3=_________________=I0?
15
ENGR1181Lab3:Circuits
LabProcedure
Lab Procedure 16
ENGR1181Lab3:Circuits
LabProcedure
Introduction and Background
TheholidayseasoniscomingupandTheLightsCompanyistryingtoimprovetheirholidaylights.
Havingreceivedcustomercomplaintsduringthepreviousholidayseason,thecompanyneedstofix
theircurrentholidaylightconfiguration.Majorityofthecustomersreportedthattheirproblem
withtheHolidaylightswasifonebulbwentout,therestofthechaindiedout.EngineersatBright
LightshavetofigureoutawaytopreventtheproblemthatTheLightsCompanyfaces,andifnot
fixedtheupcomingholidayseasonmightresultinalossforTheLightsCompany.
Yourbosshasaskedyouandateamofelectricalengineerstofigureoutasolutiontothisproblem.
TheLightsCompanydoesnothaveenoughmoneytogoandbuynewparts,thustheengineershave
toreuseasmuchoftheresistorsandLED’savailableatthecompany.Theelectricalengineers
believethatperhapschangingthetypeofcircuit(seriesorparallel)mightsolveTheLights
Company’sproblemwhilenotcostingtoomuch.
Yourteam’staskistodeterminewhichcircuittype,seriesorparallel,wouldbebestforTheLights
Company,andthenreportbackonsolvingTheLightsCompany’sdilemma.
17
ENGR1181Lab3:Circuits
LabProcedure
Circuits Lab Setup Banana Plug Wires
1 Black and 1 Red
DMM
+5 Volt
Power
Module
Breadboard
(Pre-Wired)
Circuit Components
Breadboard Connections +5 Volt Switch Box
+5 Volts Power
Ground
DMM Probe
Wires
18
ENGR1181Lab3:Circuits
LabProcedure
Task 1. Basic Setup
1.1
Plugthe+5VoltModularPowerSupplyintothepowerbaronthelabtable.Plugtheother
end(Bayonetconnector)intothe+5VoltSwitchBoxatthetoprightcornerofthe
Breadboard.PushtheswitchontheSwitchBoxtothelefttoturn+5VoltsPowerontothe
Breadboard.Noticewhichlightindicates"PowerOn".TurntheSwitchBox"Off".
1.2
SetupthebreadboardasshowninFigure19.ConnecttheDMMtotheBreadboardusing
theRedandBlackBananaPlugWiresexactlyasshown.InsertthethreeResistorBoards
Marked100Ohms,200Ohmsand300Ohmsintothecircuitboardexactlyasshown.
Figure 19: Task 1 Setup. 1.3
TurntheDMMtotheOhms(Ω)setting.UsingtheDMMProbeWires,measuretheactual
resistanceofeachresistorandrecordthemeasuredvaluesintheExcelWorksheet.
19
ENGR1181Lab3:Circuits
LabProcedure
Task 2. Lab Measurement and Calculations using Ohm’s Law and Power Law
2.1
Usingwiresandthecorrectresistor,createacircuitaccordingtotheschematic(Figure20).
2.2
Togglepoweron.
2.3
TurnDMMdialtotheDCVsetting.
2.4
Measureandrecordthepowersupply
voltage(VT)intheExcelWorksheet.
2.5
MeasureandrecordthevoltageacrossR
andverifythatthetwovoltagesareequal.
Figure 20: Circuit Diagram for Task 2
2.6
Ifyouhavetime,calculatethepowerandcurrent
in Task2onthelabworksheet.Otherwisethesecanbecalculatedafterlab.UseOhm’slaw
andthePowerlawforthecalculations.
20
ENGR1181Lab3:Circuits
LabProcedure
Task 3. Measure the Equivalent Resistance and Voltages of a Simple Series Circuit
3.1
Togglepoweroff.
3.2
Createacircuitaccordingtothe
schematic(Figure21).Note:Liningup
theresistorsiscritical.
3.3
Whilethepowerisstilloff,measure
andrecordtheequivalentresistanceof
thecircuit.
3.4
Togglepoweron.
*****CURRENTSHOULDNEVERBE
MEASUREDUSINGTHEDMM*****
3.5
MeasureandrecordV1,V2andVTotal
ChecktoseeifV1+V2=VTotal
Figure 21: Circuit Schematic for Task 3 3.6
Ifyouhavetime,usethemeasuredvoltages(Task3)andresistances(Task1)tocalculate
allremainingvaluesontheworksheet.Otherwisecompletetheseafterlab
Task 4. Measure the Equivalent Resistance and Voltages of a Simple Parallel Circuit
4.1
Togglepoweroff.
4.2
Connectthenominally‐valued200Ohmand
the300Ohmresistorsonthebreadboardas
showninFigure22.
4.3
Whilethepowerisstilloff,measureand
recordtheequivalentresistanceofthecircuit.
4.4
CalculateandrecordReqtocheckvaluefrom4.3.
UsethemeasuredvaluesofR2andR3from
Task1.
Figure 22: Circuit Schematic for Task 4 4.5
Askinstructionalstafftocheckyoursetup.
4.6
Togglepoweron.
4.7
UseDMMtomeasureandrecordvoltageacrosstheresistors.
4.8
Ifyouhavetimecalculateallthevaluesintheworksheet.Otherwisecompletetheseafter
lab.
21
ENGR1181Lab3:Circuits
LabProcedure
Task 5. Series‐Parallel Circuit 5.1
Togglepoweroff.
5.2
Connectthenominally‐valued100,200and300
OhmresistorsontheBreadboardasshowninthe
schematicdrawing(Figure23).
5.3
MeasureandrecordReqforthetotalresistance
withtheDMM.
5.4
CalculateReq1‐2‐3.UsethemeasuredvaluesofR1,
R2andR3fromTask1.
5.5
Togglepoweron.
5.6
UsetheDMMtomeasureV1,V3andVT.
5.7
Ifyouhavetimeduringlabcompletethefollowing
calculations,otherwisecompleteafterlab:



Figure 23: Circuit Schematic for Task 5 CalculatecurrentI1.UseOhm’slawandthemeasuredvalueofR1andV1fromprevious
tasksforyourcalculation.
CalculatecurrentsI2andI3byusingOhm’sLawforthetwoparallelpaths.Showyour
workontheworksheet.(Hint:calculateI3usingOhmslawandthenI2=I1‐I3.)
UsePowerlawtocalculateP2andP3.Showappropriatecalculations.
Task 6. LED Circuit
6.1
Togglepoweroff.
6.2
Connectthenominally‐valued200Ohmresistor
andtheLEDinseriestomakethecircuitshown
inFigure24.Determinethecorrectorientationof
theLEDusingthepositiveandnegativeleads.
6.3
Togglepoweron.
6.4
MeasureandrecordthevoltagesVRandVLED
Figure 24: Circuit Schematic for Task 6
22
ENGR1181Lab3:Circuits
LabProcedure
6.5
Togglepoweroff.
6.6
Removeandre‐inserttheresistorinoppositeorientation.Nowtogglepoweronandnote
thevaluesofVRandVLED
6.7
DoestheLEDglowwhenthepowerison?
6.8
Togglepoweroff;RemoveandreinserttheLEDinoppositeorientation.Nowtogglepower
onandnotethevaluesofVRandVLED
6.9
DoestheLEDglow?
6.10
Ifyouhavetimeduringlabcompletethefollowingcalculations,otherwisecompleteafter
lab:


6.11
Calculatethecurrentthroughtheresistor(usingthemeasuredvalueofR2fromTask
1),IRandthroughtheLED,ILED(Hint:HowarethecurrentthroughtheLEDandresistor
related?)
CalculatethepowerdissipatedintheLED,PLED.
UsethisactivityandthevaluesofVRandVLEDtoanswertheLabSpecificDirectionsinthe
ReportGuidelines.
23
ENGR1181Lab3:Circuits
LabProcedure
Task 7. Clean‐Up Procedure Placeallmaterialsbackintheirrespectivecontainers.
Caution:DONOTRemovethe+5VoltPowerandGroundwiresfromtheBreadboard
DONOTRemovetheDMMProbeWiresfromtheBreadboard
DONOTRemovetheSmallGoldWiresfromtheBreadboard
Attheendofthelab,yourBreadboardshouldlookexactlylikethis:
Task 8. Check‐Out Policy
Afteryouhavefinishedthelabandtheclean‐upprocedure,haveyourinstructororGTAsignthe
“End‐of‐LabSignoff”lineattheendoftherubric.Youwilllose5pointsifthisisnotsignedbyyour
Instructor/TA.
24
ENGR1181Lab3:Circuits
LabProcedure
Report Guidelines 25
ENGR1181Lab3:Circuits
LabProcedure
ENGR 1181 | Circuits Lab General Guidelines Write an Executive Summary Fordetailsoncontentandformatting,seetheTechnicalCommunicationsGuideonExecutive
Summaryspecifications.
Lab Specific Directions 
InadditiontorequirementslistedintheTechnicalCommunicationsGuide,besuretobriefly
addressthefollowingquestions.Answerwithinyoursummary,notwithnumbersor
bullets.
 ForthecircuitshowninFigure25below,explainhowcantheequivalentresistance
i.e.Reqbecalculated,inastepbystepapproach.Noequationsneedtobeprovided
forthispart.Simplyincludethethoughtprocessinvolvedinthesimplificationsteps
forcalculatingReq.
Figure 25: Parallel and Series Resistor Circuit JustifywhytheLEDglowedinjustonecaseandnottheotherinTask6.Usethe
recordedvaluesofVRandVLEDinthetwostepsoftask6tosupportyour
justification.
 WhichcircuitconfigurationwouldbebetterforTheLightsCompany(seriesor
parallel)asdiscussedintheIntroduction?Explainyourchoiceandwhytheother
circuitconfigurationwouldnotsolvethecompany’sproblem.(Hint:Iftherewere
moreLEDswhatwouldhappenifonewentoutinseries,inparallel?)
Lastly,attachintheappendixthelabworksheetandsamplecalculations.


26
ENGR1181Lab3:Circuits
LabProcedure
27
ENGR1181Lab3:Circuits
LabProcedure
28