M28_KNIG7655_03_ITG_CH28.pdf

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1、CHAPTER28TheElectricPotentialRecommendedclassdays:2minimum,3preferredBackgroundInformationOfalltheconceptsinintroductoryphysics,electricpotentialisthehardesttograspformoststudents.Itisaveryabstractidea,farremovedfrommostphenomenawithwhichtheyarefamiliar.There’sgoodevidencetha

2、tmoststudentsleaveintroductoryphysicswithlittleknowledgeoftheelectricpotentialorhowitisused.Studentsdorecognizethetermvoltagebecauseofitscommonuse.However,theyassociatevoltagewithvagueandimprecisenotionsaboutthe“flowofelectricity.”Moststudentsareunfamiliarwiththetermspotentia

3、landpotentialdifference,andeventhosewhorecognizethewordshaveessentiallynoknowledgeoftheconceptstowhichtheyrefer.Studentshaveastrongtendencytoconfusetheelectricpotentialwitheithertheelectricfieldortheelectricpotentialenergy,andtheyareliabletousethethreeinterchangeably.Afterstr

4、essingtheimportanceofvectorsforelectricfieldcalculations,andgivingmanypracticeexamplesusingvectorsuperposition,I’vebeensurprisedtofindstudentsattemptingtofindthe“components”oftheelectricpotential.Thefactthattheexpressionsforthefieldandthepotentialofapointchargelooksimilarlike

5、lycontributestostudents’misunderstanding.Theprimaryinvestigationofstudentunderstandingofthebasicconceptofelectricpotential(apartfromtheapplicationsoftheconcepttocircuits)isunpublishedworkattheUniversityofWashington.Studentstherereceivedaconventionalintroductiontotheelectricpo

6、tential.Theyalsohadalaboratoryinwhichtheyusedavoltmetertomeasureelectricpotentialsandfindelectricfieldsonweaklyconductingcarbonpaperwithpainted-onconductingelectrodes.Studentunderstandingwasevaluatedduringthelaboratory,aweekafterthelaboratoryandlectures,andonthefinalexam.Ther

7、ewasstrongevidencethatmoststudentsdidnotunderstandtheprinciplesofthelaboratoryandgainedlittleornoknowledgeofelectricpotentialfromtheexperience.Themajorityofstudentsdidn’tknowwhatthevoltmetermeasured.Whenquestioned,theystatedthatitmeasured“theflowofcharge”or“thedifferenceofcha

8、rge”betweentwopoints.Whenquestionedaboutthe28-1electricfield,nearlya