Pohl's Introduction to Physics: Volume 2: Electrodynamics and Optics

645 Pages·2018·12.7 MB·English

by  Klaus Lüders

Klaus Lüders
Robert O. Pohl
Editors
Pohl’s Introduction
to Physics
Volume 2: Electrodynamics and Optics
With videos:
Demonstrations
and biography of
Robert W.Pohl
Pohl’s Introduction to Physics
Klaus Lüders (cid:2) Robert Otto Pohl
Editors
Pohl’s Introduction to
Physics
Volume 2: Electrodynamics and Optics
Editors
KlausLüders RobertOttoPohl
FachbereichPhysik DepartmentofPhysics
FreieUniversitätBerlin CornellUniversity
Berlin,Germany Ithaca,NY,USA
Translatedby
Prof.WilliamD.Brewer,PhD,
FachbereichPhysik,
FreieUniversitätBerlin,
Berlin,Germany
Additionalmaterialtothisbookcanbedownloadedfrom
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ISBN978-3-319-50267-0 ISBN978-3-319-50269-4(eBook)
https://doi.org/10.1007/978-3-319-50269-4
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Preface to the 24th German Edition (2018) and
the 2nd English Edition (2018)
AccompanyingVolume1,thissecondvolumeof“Pohl”willbepublishedinanup-to-dateformat,
withamodernsystemofnumberingofthechapters,equationsandfiguresandwithexercisesatthe
endofeachchapter. Onceagain,wehavetakentheopportunitytocarry outacriticalreadingof
thewholetext. Alongwithnumerousclarificationsandnewformulations,wehaverevisedmany
figuresandcommentstoconformwithmodernnotationandsymbols,inordertomakereviewing
thematerialandreferencetootherliteratureasstraightforwardaspossible.
As inVolume1, wehavecarried outmajorrevisionstotheaccompanyingvideos. Inthee-book
format,theywillbereadilyaccessibleandcanbeopeneddirectlybyclickingonthelinksprovided.
ThisistruealsoofsupplementaryreferencesfromtheInternet,andofthehistoricaldocumentary
“Simplicity is the Mark of Truth – the Life and Work of Robert Wichard Pohl” by the science
journalistEkkehardSieker(seethePrefacetothe22ndedition,sidenote).Hehasdealtextensively
withthebiographyofRobertWichardPohlinGöttingen.
Onceagain,itisourpleasureanddutytoexpresslythanktheErstesPhysikalischesInstitutatthe
Georg-August-UniversitätGöttingenandtheFachbereichPhysikattheFreieUniversitätBerlinfor
generous support. Special thanks go to Prof. K. Samwer, Prof. G. Beuermann, Mr. J. Feist and
Mr.C.MahnfromGöttingen,aswellasmostespeciallyDr.J.KirsteinfromtheFreieUniversität
Berlin,withoutwhosehelpthepreparationofthevideosforthisneweditionwouldnothavebeen
possible.
The first English edition of Pohl’s “Physical Principles of Electricity and Magnetism” appeared
in1930(translated, aswashis“PhysicalPrinciplesofMechanicsandAcoustics”twoyearslater,
by Winifred M. Deans). It was published by Blackie & Son, Ltd., London and Glasgow. The
translationwasbasedonthesecondeditionofPohl’s“EinführungindiePhysik,Elektrizitätslehre”
(JuliusSpringer,1929).
Thepresentnew,secondEnglisheditionisbasedonthe24theditionof“PohlsEinführungindie
Physik”,Vol.2(ElektrizitätslehreundOptik,SpringerSpektrum,BerlinHeidelberg2018).
Again,wegratefullyacknowledgethehelpofProfessorW.D.BrewerfromtheFachbereichPhysik
oftheFreieUniversitätBerlin,notonlyforcarryingoutthetranslationofthetextwithgreatquality
andspeed,butalso,andthisisprobablyevenmoreimportant,forhishelpwiththeidentification
andclarificationofunclearpartsinthetextandinourcomments.TheEnglish-languagereaderswill
appreciatethenumerouslinksheaddedforfurtherinformation.WeowethanksalsotoE.Siekerfor
histranslationandproductionoftheEnglishversionofhisvideobiographyofR.W.Pohl,whichis
includedinthelinksforthisedition.
WealsowishtothankDr. T.SchneiderandtheSpringer-Verlag formakingthiseditionpossible,
andfortheirgeneroushelpincarryingoutitspreparationandproduction.
Berlin,Göttingen,Ithaca,March2017 K.Lüders
R.O.Pohl
v
From the Preface to the 23rd German Edition
(2009)
After the publication of Vol. 1 of R.W. POHL’s Introduction to Physics, covering the topics of
Mechanics, Acoustics and Thermodynamicsin a new, revised edition in 2008, we nowfollow it
with this Vol. 2, dealing with Electromagnetism and Optics, likewise as a newly-revised edition.
Wehaveagaintakentheopportunitytoaddsupplementalinformationwhereitseemedappropriate
tous. Inadditiontoneworrevisedcommentsandanumberofclarificationsinthetext,thenovel
features include in particular a series of videos showing demonstration experiments as well as
acollectionofexercisesforthereaders. ThechapteronFerromagnetismfromearliereditionswas
againincludedinthesectiononElectromagnetism.
The additionalvideosfor this edition were recorded underourown direction in thenew physics
lecturehallattheUniversityofGöttingen,orelseincooperationwiththePhysicsDidacticsGroup
attheFreeUniversityinBerlin. Themainpartoftheexercisesonelectromagnetismcomesfrom
theoriginalEnglish-languageeditionof1930;however,wehaveagainaddednewexercisestoboth
theElectromagnetismandOpticssections.Theydealinparticularwithquestionswhichariseinthe
text,thefigures,orthevideos,andsoprovideadditionalinformationandanaidtounderstanding
theconceptsintroduced;theyarethusintendedtomakeiteasierforthereadertoreviewanddigest
thematerialinthebook.
BerlinandGöttingen,June2009 K.Lüders
R.O.Pohl
vii
From the Preface to the 22nd German Edition
ROBERTWICHARDPOHLcompletedhisthree-volume“IntroductiontoPhysics”in1940withthe
publicationofthefirsteditionofhis“Optics”. After wehadeditedthenew, revised firstvolume
coveringthefieldsofMechanics,AcousticsandThermodynamicsin2004,wedecidedtocombine
thechaptersonthefundamentalsofElectromagnetismandOpticsintoasecondvolume. Aswith
thefirstvolume,wewantedtomakeanappropriateselectionofthematerialfromthemanyprevious
editions. The present Vol. 2 is based on the 20th editionof the “Elektrizitätslehre” and the12th
editionof“OptikundAtomphysik”,bothofwhichappearedin1967.Forthisvolume,asforVol.1,
the IWF Wissen und Medien (Institute for Scientific Films) in Göttingen prepared short videos
showingoriginaldemonstrationexperiments.TheyaremadeavailablewiththebookasaDVD.
In addition, the DVD contains the historical documentary film1 “Simplicity is the Mark of
Truth” (Original title: “Einfachheit ist das Zeichen des Wahren”, Pohl’s scientific motto; see
theComment),whichwasplanned,researchedand,togetherwiththeDüsseldorfproductionstudio
‘Kiosque’,filmedbythescientificjournalistEkkehardSieker.Thefilmoffersadetailedviewofthe
lifeandworkofRobertWichardPohlinGöttingen. ItdescribeshowR.W.Pohl,togetherwithhis
famouscolleaguesMaxBornandJamesFranck,madeessentialcontributionstoresearchandthe
teachingofphysicsinGermanyinthe1920’s.ThePhysicsInstitutesoftheUniversityofGöttingen
in those days became one of the internationally most important centers of physics. Max Born
engagedearlyoninresearchintoEinstein’stheoryofrelativityandmadeimportantcontributions
tothetheoreticalfoundationofmodernquantumtheory.JamesFranck’sresearchinterestslikewise
layinthefieldofquantummechanics,inparticularintheareasofatomicandmolecularphysics.
R.W.Pohlwasapioneerofsolid-statephysics,andthroughhisresearchandasabrilliantteacher,
heinfluencedgenerationsofphysicistsfromallovertheworld. Theexcellentstandingofphysics
inGöttingenwasbroughttoanabruptendbythepoliticaltakeoveroftheNationalSocialist(Nazi)
Party at the end of January, 1933. Max Born and James Franck were forced to emigrate from
Germany; R.W.PohlremainedasthesolephysicsprofessorinGöttingen. Hewasnotapublicly
politicalperson–hewasascientist,whoseareaofcommitmentwasinhisInstitute.
1Video:
“SimplicityistheMarkofTruth”
–theLifeandWorkofRobertWichardPohl–
http://tiny.cc/xucxny
ThetitleofthisfilmisthetranslationofPohl’sscientificmotto,“Simplexsigillumveri”,underwhichheheldhis
famouslecturesoverseveraldecades. ItwaswrittenonthefrontwallofthephysicslecturehallinGöttingen,and
wasoccasionallymistranslatedbyjokestersas“Sealingwaxistheonlytruth”. Pohl’ssuccessor,R.Hilsch,feltthat
themottowasnolongertimelyandhaditremovedduringarenovationofthelecturehallsometimelater.
“SummerFestival1952”
“ColorCenters”
“R.W.Pohl’sFarewellLecture”(Audioonly)
“Dr.h.c.forErnestRutherford”(Audioonly)
ix
x FromthePrefacetothe22ndGermanEdition
However,inthecourseofhisresearchforthefilm,E.Siekercameuponthelittle-knownfactthat
R.W. Pohlhad contacts to the civil resistance group around Carl Friedrich Goerdeler, which op-
posedtheNaziregime. FollowingthefailedassassinationattemptonHitlerofJuly20th,1944,his
friend and contact to the Goerdeler Group, teacher and lecturer Hermann Kaiser, was sentenced
to death and was executed on the 23rd of January 1945in Berlin-Plötzensee. After the German
capitulation, theBritish OccupyingForces madeR.W.Pohl, amongothers, amemberoftheDe-
nazificationCommissionfortheUniversityofGöttingen.Pohlhimselfregardeditasanobligation
oftheUniversitytomakemajorrestitutionstothescientistswhowereforcedtoleavein1933.The
filmcontainsmanyhistoricaldocumentsandinterviewswithrelatives, friendsandothercontem-
poraries,givinganexceptionalinsightintothelifeofthephysicistRobertWichardPohl.
BerlinandGöttingen,August2005 K.Lüders
R.O.Pohl
R.W. Pohl (1884–1976)
R.W. POHL(1884–1976) discussingcolorcenters(F-centers), elementarycrystallatticedefectswhichwere
discovered at his instituteand investigated there for many years. He is shown during a visit to the Ansco
ResearchLaboratoryinBinghamton,NY,intheyear1951.DetailsofPOHL’slifeandworkcanbefoundonthe
websitehttp://rwpohl.mpiwg-berlin.mpg.deoftheMaxPlanckInstitutefortheHistoryofScience(MPIWG).
There, onecanfindlinkstootherliterature,scientificinstitutionsandwebsiteswhichofferinformationand
documentsontheteachingandresearchofthefamousphysicistinGöttingen. Inaddition, thedocumentary
video“SimplicityistheMarkofTruth”byEKKEHARDSIEKER(Video1)canbefoundontheMPIWGweb
site,togetherwithalltheothervideosfrombothvolumesandotheraudiovisualmaterials,availablebothfor
videostreamingorasdownloads.
Contents
PartI ElectricityandMagnetism
1 TheMeasurementofElectricCurrentandVoltage . . . . . . . . . . . . . . . . 3
1.1 PreliminaryRemarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 ElectricCurrent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 TheTechnicalDesignofCurrentMetersorAmmeters. . . . . . . . . . 11
1.4 TheCalibrationofCurrentMetersorAmmeters . . . . . . . . . . . . . 12
1.5 TheElectricVoltageorPotentialDifference . . . . . . . . . . . . . . . . 13
1.6 TheTechnicalDesignofStaticVoltmeters . . . . . . . . . . . . . . . . . . 14
1.7 TheCalibrationofVoltmeters . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.8 Current-CarryingVoltmeters. ElectricalResistance . . . . . . . . . . . . 16
1.9 SomeExamplesofCurrentsandVoltagesofVaryingStrengths . . . 17
1.10 CurrentImpulsesandTheirMeasurement. . . . . . . . . . . . . . . . . . 20
1.11 CurrentandVoltageInstrumentswithaShortResponseTime.
Cathode-RayTubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
1.12 MeasurementsofElectricalEnergy . . . . . . . . . . . . . . . . . . . . . . 23
Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2 TheElectricField . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.1 PreliminaryRemarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.2 BasicObservations. DifferentFormsofElectricFields . . . . . . . . . . 27
2.3 ElectricFieldsinVacuum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.4 TheElectricCharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.5 FieldsinMatter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.6 ChargesCanMoveWithinConductors . . . . . . . . . . . . . . . . . . . . 37
2.7 InfluenceandItsExplanation . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.8 TheFreeChargesontheSurfaceofaConductor . . . . . . . . . . . . . 41
2.9 CurrentSourcesDeliveringHighVoltages . . . . . . . . . . . . . . . . . . 44
xiii