statement strunk rincke

On a Report by the DPG Concerning the KPC

On a Report by the German Physical Society

Concerning the

Karlsruhe Physics Course

Christoph Strunk

Karsten Rincke

Experimental and Applied Physics Science Education

Universitaumltsstr 31 D-93053 Regensburg

This text can be downloaded from

httpwwwuni-regensburgdephysikdidaktik-physikAktuellesindexhtml

Contents

1 Background and Intention

of the Present Text 1

11 Summary 112 Basic Considerations Concerning

the Karlsruhe Physics Course 1

2 MomentumCurrents in Mechanics 2

21 Rotational Transformations 322 Measurability of the Direction

of theMomentum Current 323 he Technical Addendum to the Report

On the Question of Open andClosed Integration Surfaces 4

3 Entropy and Heat in Thermodynamics 5

31 Temperature Equilibration 632 Conductivity of Entropy 633 Expansion of a gas into a vacuum 7

4 Magnetic Charge and the

Concept of Vacuum in Electrodynamics 7

41 Magnetic Charge 742 he Technical Addendum to the Report

On the Question of Sources of the H-Field 843 Ether Vacuum 8

5 Compatibility 9

6 Summary Assessment

Concerning the DPG Report 10

7 Addendum The Karlsruhe Physics Course

Competing With Other Approaches of Physics

Didactics 10

References 11

1 Background and Intention of the Present Text

11 Summary

he Report on the Karlsruhe Physics Course (KPC) com-missioned by the German Physical Society (DPG) mentionsseveral points the referees consider to be conceptual andtechnical deucircciencies Our arguments will deal with this crit-icism and relate it to established physics textbooks and tothe original texts where the KPC has been published Firsthowever we will take a professional look at the deucirccits theDPG Report claims to have found We will then ask if theconclusions drawn from them have any real basis We havecome to the conclusion that the refereesrsquo arguments are largelyunsubstantiated or have been based upon statements that arenot contained in the KPC text

In brief within a ucircxed coordinate system the momentumcurrent vector within the KPC is identical to the force theKPC relates the qualitative term lsquoheatrsquo to the scientiucircc termlsquoentropyrsquo rather than identiucircying the scientiucircc terms lsquoheatrsquoand lsquoentropyrsquo and themagnetic charges in the KPC are thesources of themagnetic ucirceld H rather than of themagneticucirceld Bmdasha notion well established in themagnetism commu-nity

It is our goal to move the discourse about the KPC to a pro-fessional level Since the report commissioned by the DPGis in German and refers to German KPC-textbooksmanycitations given in this text refer to these textbooks as wellHowever EnglishVersions of the KPC and the teacherrsquos man-ual can be found in the web1

12 Basic Considerations Concerning the Karlsruhe

Physics Course

he KPC-approach was successfully documented in an ex-tensive series of refereed publications (Herrmann amp Schmid1984 Herrmann amp Schmid 1985b Falk 1985 Herrmannamp Schmid 1985a Heiduck Herrmann amp Schmid 1987

1httpwwwphysikdidaktikuni-karlsruhedepublicationpub_fremdsprachenenglischhtml (24th May 2013)

1

C Strunk and K Rincke University of Regensburg Germany

Herrmann 2000 Grabois amp Herrmann 2000) Nearly si-multaneously and independent of the ucircrst publication ofProf Herrmann in 1978 (in German) a similar concept wasdeveloped at MIT by diSessa (1980) In addition withinthe Introductory University Physics Project (Di Stefano 1996Coleman Holcomb amp Rigden 1998) the idea to base physicsupon conservation laws rather than Newtonrsquos equations wasput forward (Moore 2003)

he KPC uses the observation that the relation between cur-rents current densities and surfaces through which currentsow is always the same for the extensive quantities chargeenergy entropy amount of substancemomentum and angu-lar momentum his approach challenges the imaginationbecause an image of what is owing can be gained by usingeveryday notions only in the case of amount of substancemdashinall other caseswe need abstract quantities forwhich appropri-atemental images must ucircrst be constructed in the classroom

It is justiucirced to ask why a teacher would want to choose aconcept based upon the ow of abstract physical quantitieshe answer can be given in at least two waysmdashempiricallyor pragmatically To answer the question empirically meansto investigate the KPCrsquos adequacy in the ucirceld ie in schoolsEmpirical investigations of the eograveectiveness of didactic ap-proaches (of the KPC as well as ofmany other approaches)have been conducted and published both nationally and inter-nationally here aremany reasons whymdashas a consequenceof these investigationsmdashone particular concept might nottake precedence so that teachers curriculum developers andresearchers in didactics would all decide for it One of thesereasons is that the expectations we have for the results of edu-cation are subject to constant social change his means thatteaching must always be in ux as well and in the best casecan make use of continuing developments he co-existenceofmany diograveerent didactic approaches can be understood asan engine for such continued developments We will returnto this in Section 7

A pragmatic answer to the question ofwhy one should choosethis concept would be the following he concepts of chargeenergy entropy amount of substancemomentum and an-gular momentum permeate all of physics To describe amultitude of various phenomena theymust be understood asabstract quantities It can be considered an essential task ofphysics teachingmdashwhether in schools or at universitiesmdashtocreate a certain familiarity with these quantities An advan-tage of the KPC is that it combines the abstract nature ofphysical quantities with a powerfully suggestivemetaphormdashthe metaphor of ow his ow is familiar in the case ofamount of substance (water for example)

he developers of the KPC see an advantage of themetaphorof a ow because a common perspective arises for diograveerentdisciplines of physics disciplines what were originally con-sidered to be diograveerent his perspective allows interconnec-tions and structural commonalities of diograveerent phenomena

he ultimate importance of this argument for the KPC canagain be discussed either empirically (see above) or norma-tively he normative answer would be one that ascertainswhether or not such a uniucirced approach should seen as a gainfor basic science education or if we should forgo this in favorof other aspects One should be aware that this is a questionconcerning theory of education and not physics

2 MomentumCurrents in Mechanics

he conceptual motivation of the KPCmakes use of the factthat despite their undoubted historical successes Newtonrsquoslaws contradict the status ofmodern physics in at least threeways

1 hey contain action-at-a-distance in which the mo-tion of a body can be transferred to other bodies atany distance by instantaneous changes to the forceshis contradicts Einsteinrsquos ucircnding that the eograveects of aforce are conveyed at ucircnite speed and cannot exceedthe speed of light

2 Newtonrsquos First Law requires concepts of (contrary tothe theory of relativity) Newtonrsquos absolute space andabsolute time Without the absolute space and timethe rsaquolinear-uniform motionlsaquo cannot be explained

3 he laws fail to describe rsaquopoint masseslsaquo (or particles)when their relative distances are of the order of the deBroglie wavelength

It is a great handicap to understanding modern physicswhena system of laws is used as the basis of a physics course thathas been considered outdated for the last 100 years becauseit suggests a world-view that is unfounded in important re-spects he commercial GPS systemprovides everybody withan experimental falsiucirccation of Newtonrsquos laws he GPS sys-temwould notwork if it did not take into account the generalrelativistic corrections to Newtonrsquos gravitation theory in itsalgorithms Until now each generation of school and uni-versity students has had the problem of needing to replacethe view of the classical physics they learned in the ucircrst yearsby moremodern concepts that contradict what before wereconsidered to be irrevocable laws Building amathematicscourse for example upon foundations that have long beenconsidered untenable would be unthinkable

he developers of theKPCmade it their goal to ease this prob-lem by introducing an alternative representation ofmechan-ics and electrodynamics based upon another basic principlethat is still valid today his basic principle is the conservationofmomentum with its corresponding continuity equationhe question of whether or not this approach is better orworse for students or pupils than the traditional one shouldbe kept separate from that of its conceptional correctness

2


he KPC interprets Newtonrsquos laws to be expressions ofmo-mentum conservation in static force ucircelds where force takesthe role of a momentum ux or momentum current heterms force andmomentum current are synonymous Use ofthe term current illustrates that a conserved quantity can onlybe altered by inward or outward ows and cannot be changedby production or destruction Newtonrsquos 2nd Law or ratherthe continuity equation for momentum currents determinesthe algebraic sign for the force or momentum current vectorrelative to the time derivative of themomentum Of coursethe force vectorrsquos sign (or the momentum current vectorrsquossign) depends upon the chosen coordinate system

In contrast to other owing quantities such as electric chargeenergy or amount of substance a vectorial nature ofmomen-tum leads to an additional mathematical complication thatmust be avoided in elementary courses in schools Since eachof the threemomentum components obeys its own conser-vation law themomentum current density G that along withthe oriented surface A determines themomentum current

F = G sdot A (1)

is not a vector but a second order tensormdashnamely the (neg-ative) stress tensor known from elasticity theory electro-dynamics or hydrodynamics2 Its elements determine themechanical state of stress of an elasticmedium hese compli-cations are avoided in the examples considered by the DPGreport

21 Rotational Transformations

In a single-dimensional case the mechanical stress is de-scribed by a simple scalar which can be either positive (com-pressive stress) or negative (tensile stress) and retains itssign when the coordinate system is inverted or rotated by180

he alleged inconsistencies described in the DPG re-port emerge because the direction of the force vector orrather themomentum current vector is mistakenly not dis-tinguished from the direction of ow of the x-componentof momentum he dashed lines with arrows in Fig 2 ofthe DPG report do not represent the vector of themomen-tum current (which is identical to the force vector drawnthere as well) but the current density vector for positive x-momentum Correspondingly theword rsaquomomentumlsaquo iswrit-ten next to the vectors (to indicate the direction of ow ofpositive x-momentum) rather than rsaquomomentum currentlsaquo Inthe original caption in the KPC the sentence raquoboth timesx-momentum ows in the negative x-directionlaquo expresses thisclearly he referees also added a Fig2c where the KPC state-ment holds as well because by rotating the x-axis as wellas the direction of ow are reversed he referees correctlywriteraquohe comparison of Figures 2a and 2c clearly illustrates that

the position of the KPC-momentum-current is closely relatedto the orientation of the coordinate systemlaquohis is logical because rotating a coordinate system causespositive x-momentum to become negative x-momentum Ifthe sign of owing charge is reversed in an electrical circuitthe orientation of the electric current density vectors willchange correspondingly

22 Measurability of the Direction of the Momentum

Current

he DPG report correctly states that the principle actio = re-actiomakes it impossible to say whether positivemomentumows to the le or negative momentum ows to the rightIt is correct that the state ofmechanical stress of an elasticmedium does not give preference to a particular directionof ow Exactly the same problem appears in electricity Anammeter cannot decide whether positive charge ows to thele or negative charge ows to the right because the Lorentzforce used to measure this as well as the electric potentialdrop will be the same in both cases he direction of owused in a technical setting is determined by the arbitraryconvention that tells us the owing charge is positive In thesubject of electricity we do not conclude from this arbitrari-ness that electric current has no raquoobjective realitylaquo and that ithas raquono placelaquo in physics as stated by the DPG referees hemethod used by the KPC for determining the direction of acurrent ofmomentum is completely analogous to the stan-dardizedmethod used to determine the technical directionof a current

he conclusions of the DPG report (p 6) stating that raquohequestion asked at the beginning of whether the KPC statementsabout direction ofmomentum currents can be checked exper-imentally must be negated For this reason the direction ofmomentum current introduced by KPC is considered an ar-bitrary convention having no objective reality his currentdoes not exist in nature herefore KPCrsquos momentum currenthas no place in physics and certainly not in physics educationlaquosimply ignores the fact that momentum current is identicalto force heKPC can avoid suchmisunderstandings bymak-ing it even clearer in the text that the concepts of force andmomentum current are synonymous

he referees concluded from themirror symmetry in theirFig 3a that the orientation of the closedmomentum currentowing in this static setup cannot be determined experimen-tally and therefore cannot exist his is of course incorrectbecause according to Eq 1 the value of themomentum cur-rent is determined by the product of themomentum currentdensity G (which in a single spatial dimension is a scalar)and a surface oriented either clockwise or counter-clockwisehe arbitrariness of the orientation of this surface vector cor-responds to the principle actio = reactio making the KPC (or

2his sign reects the diograveerent sign conventions in continuum mechanics and Newtonian mechanics

3


aM1 M2A1 A0

A2

A3 A4

A6

A5

F2

bA1

F1

A2

A4

A5

A3

Figure 1 a Illustration of a closedmomentum current circuit analogous to Fig 3 of the DPG report he spring constantthe length L of the of the springs in the relaxed state and the masses are the same so that the arrangement is perfectlysymmetrical he oriented surfaces A1 to A6 indicate the path of the closedmomentum current circuit here is tensile stressin the springs and in the horizontal part of the frame the stress is compressive Conservation ofmomentum is expressed bythe fact that the integration of the stress tensor yields the same value for the x-momentum current F

x(having the same

sign) for every one of these surfaces Shearing stress appears along the surfaces A2 and A4 through the vertical parts of theframe and the direction of the owing momentum is perpendicular to the direction of the current this is described by theoograve-diagonal elements of the stress tensor hemomentum current owing through surface A1 indicates the force by whichthe le end of the spring is pulled to the le (F1x lt 0) If the orientation of the surface is reversed as it is for surface A0 weobtain the equal and opposite force according to the actio = reactio principle by which the spring pulls the frame to the right(F0x gt 0)b If the connection between the two spheres with masses M1 and M2 is cut the circuit will be interrupted and themasseswill initially be accelerated outward Whereas the sphere on the le emits positivemomentum (F1) the sphere on the rightabsorbs positivemomentum (F2) According to the sign convention of the KPC this ows from the le via the springs andframe to the right-hand sphere If the lengths of the springs go below their rest lengths L the signs of all the local stresses aswell as the directions ofmomentum currents will reverse he spheres slow down and the well-known harmonic oscillationcentered on the equilibrium positions will be established In the initial state of b the forces acting upon the spheres (ie themomentum currents) are at amaximum but the speeds are equal to zero exactly as in the statistic () arrangement in aFor this reason a constant non-zero momentum current must ow in a whose sign is determined by the orientation of thesurfaces If the opposite sign convention of that of the KPC is used and all the surfaces are reoriented the direction of owifmomentum will change and aer interrupting the connection negativemomentum will initially ow from the sphere onthe right to the sphere on the le Physically this is the same process

another) sign convention necessary A non-zero momentumcurrent density is compatible with the symmetry of the ar-rangement because G is not a vector but a scalar or rather asecond order tensor in two or three dimensions hereforethe closedmomentum currents described by the KPC can beuniquely determined by the value of themomentum currentdensity G (themechanical stress) and the oriented surface Ahis is illustrated in the ucircgure 1 in this text which representsa symmetrical situation analogous to that in the DPG reportin both static and dynamic situations

he referees also criticize that the label rsaquopositive momen-tumlsaquo is dependent upon a reference system while the sign ofa charge is absolutemeaning it is determined independentlyof the chosen coordinate system his diograveerence though isinherent to the quantities charge and momentum and notspeciucircc to the KPC It must appear in all representations ofphysics he fact that the values of certain physical quantitiesdepend upon a reference system is not unique Relativity the-ory doesnrsquot say that such quantities have no objective reality

According to relativity theory the fundamental equationsof physics should be formulated in such a way that they areinvariant under transformation of the reference system In or-der for this to be the case the quantities in an equation musttransform in amanner that leaves the equation unchangedwhen the coordinate system is changed his criterion is sat-isucirced by both themomentum current vector (force) and themomentum current density tensor (negative stress tensor)

hemomentum current used in theKPC is nothing else thana consistently used elementary formof thewell-known physi-cal concept of the stress tensor3 Itmust perfectly have a placein physics as is illustrated by the fact that the distinguishedtextbook Landau and Lifschitz (1991 pp 14) devotes an entiresection to it under the title raquoMomentum currentlaquo

3See Kattmann Duit Gropengieszliger and Komorek (1997) for remarks about how to create elementary representations4httpwwwdpg-physikdeveroeograveentlichungstellungnahmen_gutachterkpk-ergaenzungpdf

4


23 The Technical Addendum to the Report On the

Question of Open and Closed Integration Surfaces

he same referees wrote Additional Remarks Concerning theDPG Review of the Karlsruhe Physics Course4 dated the 9thof April 2013 In the summary (p 3) they state raquohe KPC ac-tually abandons Newtonrsquos axioms and goes over to continuummechanics his obscures the fact that continuum mechanics isfundamentally based upon Newtonrsquos three axiomslaquo Althoughthis statement is correct for its part it obscures the fact thatthe continuum mechanics derived in this way is only a lim-iting case of amore general general-relativistic continuummechanics where Newtonrsquos laws are no longer valid his iswhy momentum conservation should be considered morefundamental than Newtonrsquos laws because the latter are sim-ply incompatible with modern physics he question to beanswered is whether or not the KPC allows the contents andbasic relations of school physics to be reproduced withoutundue eograveort his is the case because the contents are thesame only their interpretation is sometimes diograveerent

he authors continue raquoAcorrectmomentum current is formedby integration over c l o s ed surfaceslaquo [emphasis in the origi-nal] Instead the KPC integrates over arbitrary and especiallyopen surfaces herefore the KPC does not generally satisfyconservation ofmomentum but especially in static situationsintroduces fakemomentum currents where no staticmomen-tumowslaquo It should be noted that the referees give no reasonwhy integration over an open surface should not be allowedContrary to this statement in the case of ow phenomenaintegrating over open surfaces is the norm In the case of wa-ter owing through a pipe or electric charge owing througha wire it is obviously suotildecient to integrate over the pipe orwire cross section to ucircnd the (strength of a) current If onlyclosed surfaces were allowed only currents equal to zerowould be found for closed circuits It is impossible to inferthe vanishing of a local current density from the vanishingof a global current his is impossible because (non-zero)currents to diograveerent parts of a closed surface may add upto zero his is the case in the upper part of Fig 2 of theAddendum to the Report

Obvious examples of this fact are closed electric circuits andthe ring currents in oceans A ring current can be set inmotion by induction in a closed electrical conductor Itsexistence cannot be experimentally demonstrated by thebuild-up of charge but by themagnetic ucirceld produced by thecurrent Analogously themomentum current in amediumexpresses itself by the deformation of that medium Exactlylike the momentum current density the magnitude of thedeformation (strain) is a local quantity and is independentof whether themomentum current circuit is open or closedhis is illustrated in Fig 1a and b of our response It is ir-relevant to a state of stress of the springs whether or notit is static (closed momentum current circuit in Fig 1a) orchanges dynamically (open current circuit in Fig 1b)

he refereesrsquo reasoning boils down to denying the existenceof ocean currents by arguing that they could only be provenif the sea level somewhere were to signiucirccantly change

he referees have expendedmuch energy upon the exampleof hydrostatic pressure so we will now use this to once againexplain the argument of the KPC Consider a vertical pipeucirclled with water in a homogenous gravitational ucirceld helower end of the pipe is sealed with a valve Following theprescription of the referees we integrate the stress sensor ofthe water over the (closed) water surface and ucircnd (using theKPC rule) that a positive net current of z-momentum owsinto the water because the pressure at the lower end of thecolumn of water is higher than at the upper end Integratingover the cylindrical mantle makes no contribution henwhy isnrsquot the water set in upwardmotion Because an equalbut opposite net current of z-momentum ows out via thegravitational ucirceld (which has its own stress tensor that de-scribes the transfer ofmomentum through the gravitationalucirceld) so that the total momentum current transferred rela-tive to the water vanishes When the valve is opened andeograveects of friction are ignored the pressure diograveerence and thepositive contribution to themomentum current both disap-pear he water column then begins moving downward Isthis description really more complicated than the traditionalone

In closing we wish to respond to the refereesrsquo comment thatby eliminating Newtonrsquos ucircrst Law the concept of inertialsystem is also eliminated As Falk and Ruppel (1975 sect30)describe in detail inertial systems can be deucircned by simplyapplying the balance ofmomentumof an N-body system Aninertial system is presentwhen the bodies in it only exchangemomentumwith each other and themomentumof the centerofmass in the N-body system is constant If the latter in notsatisucirced the N-body systemmust exchangemomentumwithanother system Falk and Ruppel (1975) call this other systemthe inertial ucirceld According to the principle of equivalenceof general relativity this is identical to the gravitational ucirceldbecause it is impossible to decidewhether the N-body systemis accelerated by a gravitational ucirceld or if the reference sys-tem used is being accelerated and is therefore not an inertialsystem he referees have used an invalid objection again

3 Entropy and Heat in Thermodynamics

For the last 150 years introductions to thermodynamics havesuograveered from conceptual diotildeculties having to do with themultitude of changes to themeaning of theword rsaquoheatlsaquo hesediotildeculties are demonstrated by the fact that the subject of rsaquoex-perimental thermodynamicslsaquo is unpopular even among stu-dents at university level he usual deucircnition for rsaquoheatlsaquo usedby physicists today is raquoheat is a form of energylaquo Unfortu-nately this deucircnition actually says nothing at all becauseenergy is by no means speciucircc to thermodynamics It is

5


found everywhere in physics If we wish to introduce theenergy form rsaquoheatlsaquo as opposed to other forms of energy notonly qualitatively (raquoheat is random motionlaquo) but by measure-able quantities we will have to use entropy New universitylevel textbooks (Kittel amp Kroumlmer 2001 Schroeder 2000Stierstadt 2010) acknowledge this by introducing entropyfrom the start by its relation to statistical physics To datethis is not done in schools because the basic concepts havenot been made available in current didactics As so oen theconcept of entropy introduced phenomenologically

Right from the beginning theKPC structures thermodynam-ics in a way that conforms with this specialized branch ofscience by using conjugated pairs of extensive and intensivequantities instead of using the energy forms heat and workas inexact diograveerentials To do so the KPC relates entropy tothe everyday perception of heat without describing entropyas a new type of substance (just as it would not describe en-ergy electric charge or momentum as a substance) Heathas no unit in everyday life (not even the Joule) because wedo not measure there It has been suotildeciently documentedhow the everyday concept of heat interfereswith temperature(compare for example Duit 1986 Kesidou amp Duit 1993)Introducing the physical concept of rsaquoheatlsaquo in school can beconsidered a standard problem as long as it is made clearin class what is meant by it scientiucirccally and what is nothe assignedmeanings in this case are assertions and do notnecessarily result from scientiucircc considerations because ev-eryday terms are not scientiucircc terms To relate the every-dayterm rsaquoheatlsaquo to the technical term heat by introducing thetechnical term heat as a transfer form of energy is not theonly possibility We can just as well point out the closeness ofthe every-day term rsaquoheatlsaquo with the technical term entropy Inboth cases students will have to reinterpret their every-dayconcept if they want to argue scientiucirccally

he authors of the KPC promote their assertion statingthat the physical quantity entropy is very similar to the pre-scientiucircc everyday idea of rsaquoheatlsaquo his allows an intuitiveunderstanding of a diotildecult quantity independent of thestatistical interpretation of entropy but compatible with ithe relation between entropy and thermal energy transfer isonly developed later on (a discussion of the relation betweenchronology of introduction and conceptual hierarchy can befound in Section 7) his is analogous to electricity whereinitially electric charge is introduced then electric currentand next electric conductivity he fact that energy is alwaystransferred along with charge is discussed only later

If one decides to introduce entropy and not energy as thetypical quantity for thermal phenomena a unit is needed Inthe KPC the unit Carnot (Ct) is introduced for this As soonas the relation to energy has been established the units ofentropy and energy can be related to each other Ct = JKhe referees claim that in the KPC the entropy and the scien-

tiucircc term heat have been made synonymous his statementis nowhere to be found in theKPC textbook Instead entropyis introduced as a basic quantity for describing thermal phe-nomena It also states that it has a lot of similarity to what iscalled rsaquoheatlsaquo in everyday life he statement about this in theKPC is correct without a doubt However the referees aremistaken if they assume that the connection between every-day and specialized scientiucircc terminology exists a priori andis not created in the classroom5 We consider it incorrect todeclare the assertion everyday term rsaquoheatlsaquo = specialized scien-tiucircc term heat as absolute and then raquoidentifylaquo a fundamentalmistake on this basis

he commentaries about thermodynamics in the DPG reportare to be found under the titles Temperature equilibrationExpansion of a gas into a vacuum and Conductivity of entropyWe will begin with the ucircrst and last of these three pointsbecause they relate closely to each other

31 Temperature Equilibration

he referees make a special demand of the KPCWe wouldnormally expect a ucircrst introduction to the simplest thermalphenomena on the ucircrst pages of a textbook (as it is done onpage 7 ofHerrmann 2010b) In contrast the referees demandthat these phenomenamust be completely explained rightthere raquoIf entropy has to be introduced already as is done inthe KPCmdashwhich in this case constitutes a complicationmdashit isnecessary to explain its role in natural processes correctly andcompletely he KPC does not do thislaquo

his excessive demand contradicts the basic assumptionsunderlying any successful elementary exposition Beyondthis the statement is false because the relationship betweenentropy transfer and energy transfer is explained a couple ofpages later in Section 110 on page 17 Entropy generation inheat transfer is explained in Section 111 on page 19

How should this criticism be understood Are the refereesactually accusing the KPC of dedicating too much space (ie12 pages) to introducing all the phenomena of heat transferand introducing all the quantities which are necessary to aquantitative description

32 Conductivity of Entropy

he referees are of the opinion that the concept of entropyconductivity is unsound becausemore entropy ows into thecold end of a conductor than is released at the hot end How-ever it should be noted that the amount of entropy owingaway is in fact proportional to the temperature diograveerence∆T whereas the amount of entropy produced is proportionalto ∆T 2 In any case the process of heat conduction can onlybe described for small enough ∆T by a linear relation between

5In everyday life when the word rsaquoforcelsaquo is used oen it is used in terms closer to rsaquopowerlsaquo or rsaquoenergylsaquo rather than force in mechanics

6


∆T and the entropy current IS or the energy current I

E re-

spectively his implies that nonlinear contributions given byσS(T ) = λ(T )T where λ(T ) is the conventional conductivity

deucircned in terms of the energy current must be negligiblehe proportionality between σ

S(T ) and λ(T ) is justiucirced by

the equation IE= T sdot I

S(Eq 10 in Section 110) for the relation

between the energy current and entropy current on surfaceswith constant temperature For this reason the concept ofentropy conductivity easily agreeswith the conventional heatconductivity as deucircned by Fourierrsquos law

33 Expansion of a gas into a vacuum

he referees object to the description of irreversible expan-sion of a (not necessarily ideal) gas into a vacuum in Section27 his is based upon the way the referees chose to interpretthe observations on page 41 of the KPC

1 When entropy is added to a gas its temperature rises

2 when a gas is expanded at constant entropy the tem-perature decreases

as relating directly to the process of free expansion into avacuum his is nowhere to be found in the KPC text heauthors of the KPC only remind readers at this point aboutwell-known characteristics of gases in order to justify pos-sible expectations for the experimental result6 In order toavoid the complications that arise with this process in realityonly the starting and end states before and aer expansion areconsidered Instead of considering the complicated and diotilde-cult to describe process of irreversible expansion the KPCauthors have replaced the actual process by two consecutivereversible ersatz processes hese processes are an isentropicexpansion while performing work and an isochoric heatingin which the same amount of energy withdrawn during theucircrst process is fed back from a heat reservoir along with thecorresponding amount of entropy Crucial to the conclusionsdrawn from this that the temperature of an (ideal) gas un-dergoing an irreversible process is the same in its initial anducircnal status is the fact that the starting and end states of thegases in the real and reversible ersatz processes are identicalhis fact justiucirces the statement in the KPC that raquoBoth eograveectscancel each other outlaquo

Authors of conventional textbooks call such an approachthe only possible one (compare Nolting 2005 p 179 forexample) because the traditional representation of thermo-dynamics tells us that only reversible processes can be dealtwith quantitatively his is because in the case of irreversibleprocesses changes of entropy are diograveerent than the sumof en-tropy owing in and owing out Why should this approach

which is found in conventional textbooks be inadmissiblefor the authors of the KPC

he reviewers write raquohe attempt by the KPC to center ther-modynamics solely around entropy and temperaturemust beviewed as physically mistaken and leading to false conclusionsIt equates two diograveerent physical quantities thereby making anelementary mistake Putting the fundamentally wrong iden-tiucirccation of entropy and heat at the beginning immediatelyleads to contradictions As the examples above have shown theauthors themselves have fallen for this as can be seen in theirdescription of expansion of an ideal gas in a vacuum Howcan this approach be easier for school pupils to understandWhereas the physically correct explanation of entropy as thequantity deciding about the course of irreversible processes anddenoting the number of states a system can take is missing theKPC introduces entropy as a complication at a point where theconcept of quantity of heat would suotildecelaquo he referees haveproved wrong statements that are either not in the KPC textor are scientiucirccally correct and then they admonish the lackof important statements in the text that are actually there

4 Magnetic Charge and the Concept of Vacuum in

Electrodynamics

41 Magnetic Charge

he referees write raquoPaul Dirac speculated that magneticcharges and amagneticmonopole could exist as elementaryparticles he existence of magnetic charge would eliminatethe asymmetry between the electric ucirceld and the magneticux density in Maxwellrsquos equations Despite intensive eograveortit has not been possible to experimentally prove the existenceof isolatedmagnetic charges Contrary to this experimentallyproven fact which is acknowledged in the teaching manual forelectrodynamics (p 15) of KPC [2]7 the KPC assumes in thetextbook for secondary level 2 Volume 1 Electrodynamics [3]8

the existence ofmagnetic charge (p 41)laquo

his passage is doubly surprising because

1 One can hardly claim that the non-existence ofmag-neticmonopoles can be experimentally veriucirced hisgoes against the general and basic epistomological po-sition of empiric science which states that the non-existence of an experimental ucircnding can be falsiucircedbut never veriucirced

2 he referees assume that the objects called rsaquomagneticchargelsaquo by the KPC aremagneticmonopoles his isexplicitly contrary to the actual text in the KPC whereit is stated that raquohe total magnetic charge of amag-

6he gas in the ucircrst container expands approximately adiabatically and initially cools down while the gas owing into the originally empty secondcontainer is adiabatically compressed and initially warms up until the process of heat conduction leads to a temperature equilibrium between the twocontainers Only this common end temperature can be compared to the starting temperature

7Herrmann (2002)8Herrmann (2010a)

7


net is zero [emphasis in the original] his diograveers fromelectric charge A body can be given a [] small electricnet charge his diograveerence between an electric chargeand amagnetic charge is very important It means thatthere are electric currents (owing electric charge) butno magnetic currents (owing magnetic charge)laquo Ob-viously the authors of the KPC ucircnd it very importantfor the readers to avoid exactly themisconception thatmagnetic charge is identical to magneticmonopolesand to make the reader aware of the central diograveerencebetween freelymoving electric charge and boundmag-netic charge Nevertheless the reviewers again con-clude that raquohe obvious experiment for this is to sawa bar magnet into two parts (compare Fig 6) As weknow doing this produces two new bar magnets andno isolated charge his is not an isolated case but asalready stated above the search for magneticmonopoleshas remained unsuccessful herefore there is no exper-imental justiucirccation for magnetic charges up to todaylaquo

hese statements stand in opposition to the ones in highlyregarded classical textbooks One example is in the new edi-tion ofGerthsenrsquos textbooks by one of the referees (Meschede2006 p 363) raquohere are certain cases where it would seemobvious that the image of spatially concentrated rsaquomagneticchargelsaquo should be used In the case of long solenoids or barmag-nets (length l) point-like rsaquomagnetic chargeslsaquo or pole strengthsplusmnP could be attached to pole shoeswhere almost all B-lines con-verge or diverge so that themagneticmoment of the solenoidor bar is given by micro = P l laquo

It is therefore even more surprising that the DPG reportcontinues with the following statement raquohe question is notwhether magnetic charge exists or not but whether introduc-ing it serves any purpose his is an argument that completelydiscredits the KPC in the eyes of serious scientists It is anobvious example of how the KPC bends fundamental physicalfacts to ucirct didactic convictionslaquoAgain statements in theKPCare said to be wrong or misleading even when similar state-ments can be found in established conventional textbooks Ifthe text (Herrmann 2010a pp 41) is looked at with unprej-udiced eyes it is obvious that the KPC authors are talkingabout magnetic surface charges as is done in conventionaltextbooks (Meschede 2006 Jackson 1975) and not magneticmonopoles

his is said explicitly in the KPC-text in the sentence pre-ceding the critized one raquoMagnetic surface charges on a per-manent magnet can be introduced by analogy with boundelectric charges on the surface of a polarized dielectric mate-riallaquo (Herrmann 2002)

he referees continue raquohe referees of the DPG are of the opin-ion that even in schools only experimentally provable factsmaybe taught for which a didacticmethodmust be found and that

physical rsaquofactslsaquo may not be invented so that a didacticmethodappears more elegantlaquoWe consider that this statement canbe agreed upon and that it is generally shared However upto this point (and beyond) proof that the KPC authors haveinvented experimental facts is missing

42 The Technical Addendum to the Report

On the Question of Sources of the H-Field

In their addendum to the report the authorsmdashin a puzzlingand surprising contradiction to their own reportmdashdedicateseveral pages to explain things that are seen in exactly thesame way by the KPC namely that the sources of the H-ucirceldare sinks ofmagnetization M However the authors rigidlystand by their view that themagnetic charges described in theKPC are themagneticmonopoles in the Dirac sense Evenwhen considered in a charitable light this view is a clearmisleading his can be clearly seen in F Herrmannrsquos lecturenotes9 wheremagnetic and electric quantities are related toeach other and where rsaquomagnetic phantom chargeslsaquo at theends of amagnet are explicitly discussed Even more clearlythe author adds that the analog electric charge density onthemagnetic side should be set equal to zero raquobecause freemagnetic charge does not existlaquo (page 52 below)

As the referees conclude in their addendum it is just as possi-ble to describe the B-ucirceld of a permanentmagnet byAmperersquosmolecular currents namely the bound (electric) surface cur-rents micro0rot M his yields exactly the same relations betweenB H and M as the (also bound) magnetic surface chargesthat the KPC uses in its description he latter are perfectlyanalogous to the polarization charges bound to surfaces thatoccur in conjunction with dielectricmedia Again there isan example in which two diograveerent explanations (magneticsurface charges vs electric surface currents) lead to exactlythe same phenomenology and cannot therefore be experi-mentally distinguished A disadvantage of electric surfacecurrents is that themagnetic ucirceld of permanent magnets areusually created by electron spins which as we well knowcannot be explained by orbital motion of an electric charge

43 Ether Vacuum

he DPG report of this section begins as follows raquohe KPCasks the question ([4]10 p46) rsaquoWhat does the electromagneticwave actually travel through Who or what functions here asthe carrierlsaquo Although starting with Fizeaursquos experiments andthen those ofMichelson andMorley modern physics has ex-cluded the possibility of such a carrier the KPC continues ([4]p46) rsaquoAer this [apparently aer these experiments (com-ment by the referees)] it [the carrier (comment by the ref-erees)] was given a diograveerent name because the word ether

9httpwwwphysikdidaktikuni-karlsruhedeskripten (19th April 2013)10Herrmann (2010c)

8


brought up too many obsolete images his new name is lsquovac-uumrsquo in English lsquoemptinessrsquo he carrier of electromagneticwaves is called lsquovacuumrsquo [] If one says that in a region of spacea vacuum can be found it means that although there is nochemical matter to be found there something else ismdashnamelythe carrier of electromagneticwaves As long as nowave travelsthrough the vacuum the vacuum is said to be in its lsquogroundstatersquolaquo

he KPC authors clearly state here that the word ether is con-nected to antiquated ideas that they do not share Nonethe-less the referees accuse themof an antiquated understandingnamely that the word rsaquocarrierlsaquo means the same as the termrsaquoetherlsaquo which stems from the early 20th century We ucircnd thisaccusation to be unfair because in the next passage the KPCauthorswrite raquoPeople used to think that lightwas amechanicalwave in this ether which makes the carrier move exactly likethe air moves as the result of sound waveslaquo he KPC authorshave clearly distanced themselves from the ether model thathas long been disposed of Irregardless the referees continuewith their comments raquohe KPC argues that although theword etherwas eliminated as a consequence of the experimentselectromagnetic waves still have a carrier medium (similar tosound waves) When so expressed it causes misleading if notfalse ideaslaquo

In our opinion the KPC authors have been wrongly accusedof saying that electromagnetic waves have a carrier of thesame type as the one sound waves have

It is remarkable that the referees then write raquohey [electro-magnetic waves comment by the authors] do not need theether or the vacuum as a carrier mediumlaquo but then alreadyrelativize their conviction in the next sentence raquoIn fact basedupon quantum theory the vacuum can be considered amodernsuccessor to the etherlaquo he KPC states exactly this on page46 he referees continue to clarify raquoHowever a decisivediograveerence to the classical ether is that the vacuum of quantumucirceld theory is Lorenz invariant so that it satisucirces the theoryof relativity and does not single out a reference systemlaquo hisis without a doubt correct Correspondingly nowhere inthe KPC do we ucircnd the statement that the carrier mediumdiscussed there would single out a reference system Howcould a vacuum single out a reference system

he refereesrsquo thesis that raquohe examples given here show thataccording to the present state of scientiucircc knowledge the KPCmakes false statements (the existence of magnetic charge ormonopoles) or creates false images by imprecise formulations(vacuum)laquo cannot be documented by texts in the KPC

5 Compatibility

he question of compatibility is an important one that shouldbe discussed Unfortunately although the referees asked thequestion they only answered it in a very limited way raquoIt

is the task of physics teaching to represent the current stateof physics so that students can understand the phenomena ofnature and technical devices [] To do so school physicsmust hold to the national and international terminology inuse today that has made the dialog both inside and outsidethe world of physics possible and has also stood the test of timewhen checked against experiments hemomentum current ofthe KPC does not fulucircll these requirements as its terminologyis not found in nationally and internationally disseminatedcommon books for students of physics Just a look at the indexin various textbooks proves this For example in the textbookGerthsen Physics [6] the term force is referred to 14 times andmomentum current is not mentioned at alllaquo

Aer negating the scientiucircc relevance of rsaquomomentum cur-rentlsaquo in great detail the DPG report then limits itself to stat-ing which terminology is in general use Counting indexentries seems an insuotildecient method for determining whichterms are shared by the scientiucircc community and to whatextent Even if it came to using these ucircndings as a reasonto accept or reject a term we would like point out that the23rd edition of Gerthsen (Meschede 2006) uses the conceptofmomentum current several times in the body of the text(p 171 and p 239) In other words it appears that this termwhich is completely identical with the term force is compati-ble with more conventional descriptions in physics Otherreputable texts use this term aswellmdashin Landau and Lifschitz(1991) the term rsaquomomentum current densitylsaquo even appearsin the otherwise very short index

Regarding the refereesrsquo criticism of introducing units thatare not generally used in physics we agree Even thoughthe developers of the KPC consider them useful we believethat the potential problems of communication resulting fromthem should be avoided

Amuch more important question however is what the ad-vantages and disadvantages are for pupils who have beentaught according to the KPC before they begin a furthereducation and later enter into their professional lives Indiscussions about the KPC it is oen said that pupils andstudents who have been taught according to the KPC can-not participate as equals in discourse about subjects in thenatural sciences because they have only marginally learnedand practiced concepts such as rsaquoforcelsaquo he term momentumcurrent is said to be unusual in everyday life

At ucircrst glance this rings true However it is also true thatthe concept of forcemdashas introduced by other approaches andas understood by expertsmdashis associated with the intendedimages only by aminority of students According to investiga-tions of this topic general ideas about of rsaquoforcelsaquo are very closeto those of rsaquoenergylsaquo rsaquovitalitylsaquo or rsaquomotionlsaquo It is important torealize that when the word rsaquoforcelsaquo is used in everyday life aswell as in popular scientiucircc literature the partner in commu-nication will in many cases activate varied colorful imagesand very little will comply with the intensions of physics

9


education

Just because there are problems of understanding connectedwith the term force it shouldnot be assumed thatmomentumcurrent is any better without ucircrst having signiucirccant empiri-cal investigations to support this Such investigations shouldinform us about what pupils and students who have receivedthe KPC and those who have learnedmechanics in anotherway experience later on in their studies and working lives

In regard to ensuring the compatibility of theKPCwewouldask its developers to comply with certain things We con-sider a statement like raquohe namemomentum current for thequantity F has existed since the beginning of the last centuryHowever the name force for the quantity F is still widely inuse today and is found much more oen than the name mo-mentum currentlaquo (Herrmann 2010d p 32) not to be helpfulfor reaching this goal We consider this an attempt to decidewhich term rsaquoforcelsaquo or rsaquomomentum currentlsaquo is the one of thefuture Just as we criticized the referees for doing this whichled to counting words in glossaries we also criticize the KPCauthors for attempting to decide which term should be usedpreferably by the scientiucircc community

6 Summary Assessment Concerning the DPG Report

Of course the scientiucircc questions raised in the DPG reportand the question of compatibility are legitimate ones Wehope that these have been answered here and that it can beseen that the basic ideas of KPC are scientiucirccally correct andthe criticisms of the referees are unfounded

As to the question of compatibility we are convinced thatthis can only be answered by systematic credible empiricalinvestigations We consider the arguments in the report to betoo superucirccial In the following we wish to make some com-ments about how the KPC is perceived by physics didacticsand in physics

7 Addendum

The Karlsruhe Physics Course Competing

With Other Approaches of Physics Didactics

Discussions about the Karlsruhe Physics Course over the lastthree decades have always shown that it is considered exoticAt this point we will venture an opinion as to where thismight come from

he developers of theKPC have followed a very well foundedconcept It is the idea of the ow of physical quantities hemechanics course for the secondary school level logically be-gins with an introduction to momentum as a substance-like

quantity (Herrmann 1995 pp 25) he text discusses thecharacteristics of this quantity which is new to the studentsin relation to the quantities velocity andmass of bodies Allthis is embedded in a series of simple examples from everydaylife Only on page 39 is the concept ofmomentum currentintroduced and then on page 40 it is identiucirced as synony-mous to the word force11 he decision by the developers ofKPC to use ows of quantities as their central theme requiresa certain chronology for introducing its terminology Insome sense this chronology also maps onto the hierarchy ofterminology according to which the course operatesmdashbasicconcepts are introduced earlier than the ones that are derivedfrom them Momentum appears as a basic term upon whichlater considerations ofmechanics are built he decision fora certain governing design idea induces a speciucircc hierarchyof terminology a speciucircc order to the terminology but itdoes not mean that new physical quantities were invented12

he (illegitimate) equating of the perceived newness of termi-nology with a newness of order of old terminology appearsto us to be amajor source ofmisunderstandings

It should be emphasized that the decision for a certain gov-erning idea necessitatesmdashfor every conceptmdasha chronologyfor introducing terminology for each one and each one willlead to its own order of concepts To clarify this we will usethe concept for mechanics whose basic ideas were formu-lated by Walter Jung in the 1970s and further developed byH Wiesner and his colleagues at the LMU Munich in the1990s (compare among othersWiesner 1994Wodzinski ampWiesner 1994aWodzinski ampWiesner 1994bWodzinski ampWiesner 1994c) Today it exists in adapted form as a text-book for schools (M Hopf TWilhelm CWaltnerV TobiasH Wiesner)13 he developers of this concept use the ideathat motion cannot be physically described as a whole (asterms such as rsaquocircular motionlsaquo and rsaquomotion along a straightlinelsaquo unfortunately suggest) but only pointwise A furthercentral idea is that of the interaction of bodies which makesitself felt when a change to direction or speed (absolute valueof velocity) is observed hese ideas require that the conceptemphasizes the term direction which assumes a vectorialconcept of velocity right from the beginning (diograveerently thanmany conventional concepts as well as the KPC) and intro-duces an at ucircrst sight unusual deucircnitional relation betweenforce mass change of velocity and period of interactionF sdot ∆t = m sdot ∆v Here as well no new terminilogy let aloneany new physics is being produced but raquoonlylaquoa certain orderto the terminology

Diograveerent conceptual orders as they are developed in diograveerentdidactic designs lead to diograveerent priorities in teaching anddiograveer in their usefulness for describing domains of phenom-ena Each one can counteract in its own way the everyday

11Introducing the new term rsaquomomentum currentlsaquo mitigates the problem of polysemy which always emerges when terms of everyday life (rsaquoforcelsaquo) are givennew meanings in physics

12It must be noted that the introduction of of new units likeHuygens or Carnot should not bemistaken for introducing new basic terminology13he textbook (german) can be downloaded from httpwwwthomas wilhelmnetMechanikbuch_Druckversionpdf (19th April 2013)

10


concepts thathinder learning If an approach should be testedfor its appropriatness for schools diograveerent questions needto be asked concerning its eograveect How should the quality ofthe knowledge gained in class be rated What valuation ofand attitude toward the science of physics is promoted by theapproach How much does it encourage the development ofmotivation and interest Towhat extent are the everyday con-cepts that hinder learning replaced by those that can easilybe connected to science

he competition between diograveering didactic approaches isa competition on many levels that can only convincinglytake place through intensive empirical work he reexiveresponse of rejecting the unfamiliar and using onersquos personalexperiences as a student as a reference for what is or is notappropriate to teaching does not lead anywheremdashespeciallynot when university teachers who have always belonged totheminority () of people who have grasped physicss despiteall the shortcomings and contradictions involved teachingand learning physics at school exhibit this reex

References

Coleman AAHolcomb D Famp Rigden J S (1998) he in-troductory university physics project 1987ndash1995Whathas it accomplished American Journal of Physics66(2) 124 ndash 137

Di Stefano R (1996) he IUPP evaluationWhat we weretrying to learn and how we were trying to learn itAmerican Journal of Physics 64(1) 49 ndash 57

diSessa A (1980) Momentum ow as an alternative per-spective in elementarymechanics American Journalof Physics 48(5) 365 ndash 369

Duit R (1986) Waumlrmevorstellungen Naturwissenscha imUnterricht 34(13) 128 ndash 131

Falk G (1985) Entropy a resurrection of caloric a look atthe history of thermodynamics Euorpean Journal ofPhysics 6 108 ndash 115

Falk G amp RuppelW (1975) Mechanik Relativitaumlt Gravi-tation BerlinHeidelbergNew York London ParisTokyo Springer

GraboisM ampHerrmann F (2000) Momentum ow dia-grams for just-rigid static structures Euorpean Journalof Physics 21 591 ndash 601

Heiduck G Herrmann F amp Schmid G B (1987) Momen-tum ow in the gravitational ucirceld Euorpean Journalof Physics 8 41 ndash 43

Herrmann F (1995) Der Karlsruher Physikkurs ndash EnergieImpuls Entropie Karlsruhe UniversitaumltsdruckereiKarlsruhe

Herrmann F (2000) he karlsruhe physics course Euro-pean Journal of Physics 21 49 ndash 58

Herrmann F (2002) Ein Lehrbuch fuumlr die Sekundarstufe II

Teil 1ElektrodynamikUnterrichtshilfen HallbergmoosAulis

Herrmann F (2010a) Der Karlsruher Physikkurs 1 Elektro-dynamik Ein Lehrbuch fuumlr die Sekundarstufe II Hall-bergmoos Aulis

Herrmann F (2010b) Der Karlsruher Physikkurs 2 hermo-dynamik Ein Lehrbuch fuumlr die Sekundarstufe II Hall-bergmoos Aulis

Herrmann F (2010c) Der Karlsruher Physikkurs 3Schwingungen Wellen Daten Ein Lehrbuch fuumlr dieSekundarstufe II Hallbergmoos Aulis

Herrmann F (2010d) Der Karlsruher Physikkurs 4Mechanik Ein Lehrbuch fuumlr die Sekundarstufe II Hall-bergmoos Aulis

Herrmann F amp Schmid G B (1984) Statics in themomen-tum current picture American Journal of Physics 52146

Herrmann F amp Schmid G B (1985a) Analogy betweenmechanics and electricity European Journal of Physics6 16 ndash 21

Herrmann F amp Schmid G B (1985b) Momentum ow inthe electromagnetic ucirceld American Journal of Physics53 415

Jackson J D (1975) Classical electrodynamics JohnWileyamp Sons

Kattmann U Duit R Gropengieszliger H amp Komorek M(1997) Das Modell der didaktischen Rekonstruk-tion ndash ein Rahmen fuumlr naturwissenschasdidaktischeForschung und Entwicklung Zeitschri f ur Didaktikder Naturwissenschaen 3(3) 3 ndash 18

Kesidou S amp Duit R (1993) Studentsrsquo conceptions of thesecond law of thermodynamicsmdashan interpretive studyJournal of Research in Science Teaching 30(1) 85ndash106Available from httpdxdoiorg101002tea

3660300107

Kittel C amp KroumlmerH (2001) hermodynamik MuumlnchenWien Oldenbourg

Landau LDamp Lifschitz EM (1991) Lehrbuch derheoretis-chen Physik (Vol 6WWeller Ed) Berlin Akademie

Meschede D (Ed) (2006) Gerthsen Physik Berlin uaSpringer

Moore T A (2003) Conservation laws constrain interac-tions (Vol 1) New York McGraw-Hill

NoltingW (2005) GrundkursheoretischePhysik 4 SpezielleRelativitaumltstheorie hermodynamik Berlin Heidel-berg New York Springer

Schroeder D V (2000) hermal Physics San FranciscoReading New YorkHarlow Don Mills SydneyMex-ico CityMadrid Amsterdam Addison Wesley Long-man

Stierstadt K (2010) hermodynamik von der Mikrophysikzur Makrophysik BerlinHeidelberg Springer

Wiesner H (1994) Verbesserung des Lernerfolgs im Unter-richt uumlberMechanik Physik in der Schule 32 122 ndash 127

11


Wodzinski R ampWiesner H (1994a) Einfuumlhrung in dieMechanik uumlber die Dynamik Physik in der Schule32(5) 165 ndash 169

Wodzinski R ampWiesner H (1994b) Einfuumlhrung in dieMechanik uumlber die Dynamik Physik in der Schule

32(10) 202 ndash 207Wodzinski R ampWiesner H (1994c) Einfuumlhrung in die

Mechanik uumlber die Dynamik Physik in der Schule32(10) 331 ndash 335

12

Background and Intention of the Present Text

Summary

Basic Considerations Concerning the Karlsruhe Physics Course

Momentum Currents in Mechanics

Rotational Transformations

Measurability of the Directionof the Momentum Current

The Technical Addendum to the Report On the Question of Open and Closed Integration Surfaces

Entropy and Heat in Thermodynamics

Temperature Equilibration

Conductivity of Entropy

Expansion of a gas into a vacuum

Magnetic Charge and the Concept of Vacuum in Electrodynamics

Magnetic Charge

The Technical Addendum to the ReportOn the Question of Sources of the -Field

Ether Vacuum

Compatibility

Summary AssessmentConcerning the DPG Report

Addendum The Karlsruhe Physics CourseCompeting With Other Approaches of Physics Didactics

References


Herrmann 2000 Grabois amp Herrmann 2000) Nearly si-multaneously and independent of the ucircrst publication ofProf Herrmann in 1978 (in German) a similar concept wasdeveloped at MIT by diSessa (1980) In addition withinthe Introductory University Physics Project (Di Stefano 1996Coleman Holcomb amp Rigden 1998) the idea to base physicsupon conservation laws rather than Newtonrsquos equations wasput forward (Moore 2003)

he KPC uses the observation that the relation between cur-rents current densities and surfaces through which currentsow is always the same for the extensive quantities chargeenergy entropy amount of substancemomentum and angu-lar momentum his approach challenges the imaginationbecause an image of what is owing can be gained by usingeveryday notions only in the case of amount of substancemdashinall other caseswe need abstract quantities forwhich appropri-atemental images must ucircrst be constructed in the classroom

It is justiucirced to ask why a teacher would want to choose aconcept based upon the ow of abstract physical quantitieshe answer can be given in at least two waysmdashempiricallyor pragmatically To answer the question empirically meansto investigate the KPCrsquos adequacy in the ucirceld ie in schoolsEmpirical investigations of the eograveectiveness of didactic ap-proaches (of the KPC as well as ofmany other approaches)have been conducted and published both nationally and inter-nationally here aremany reasons whymdashas a consequenceof these investigationsmdashone particular concept might nottake precedence so that teachers curriculum developers andresearchers in didactics would all decide for it One of thesereasons is that the expectations we have for the results of edu-cation are subject to constant social change his means thatteaching must always be in ux as well and in the best casecan make use of continuing developments he co-existenceofmany diograveerent didactic approaches can be understood asan engine for such continued developments We will returnto this in Section 7

A pragmatic answer to the question ofwhy one should choosethis concept would be the following he concepts of chargeenergy entropy amount of substancemomentum and an-gular momentum permeate all of physics To describe amultitude of various phenomena theymust be understood asabstract quantities It can be considered an essential task ofphysics teachingmdashwhether in schools or at universitiesmdashtocreate a certain familiarity with these quantities An advan-tage of the KPC is that it combines the abstract nature ofphysical quantities with a powerfully suggestivemetaphormdashthe metaphor of ow his ow is familiar in the case ofamount of substance (water for example)

he developers of the KPC see an advantage of themetaphorof a ow because a common perspective arises for diograveerentdisciplines of physics disciplines what were originally con-sidered to be diograveerent his perspective allows interconnec-tions and structural commonalities of diograveerent phenomena

he ultimate importance of this argument for the KPC canagain be discussed either empirically (see above) or norma-tively he normative answer would be one that ascertainswhether or not such a uniucirced approach should seen as a gainfor basic science education or if we should forgo this in favorof other aspects One should be aware that this is a questionconcerning theory of education and not physics

2 MomentumCurrents in Mechanics

he conceptual motivation of the KPCmakes use of the factthat despite their undoubted historical successes Newtonrsquoslaws contradict the status ofmodern physics in at least threeways

1 hey contain action-at-a-distance in which the mo-tion of a body can be transferred to other bodies atany distance by instantaneous changes to the forceshis contradicts Einsteinrsquos ucircnding that the eograveects of aforce are conveyed at ucircnite speed and cannot exceedthe speed of light

2 Newtonrsquos First Law requires concepts of (contrary tothe theory of relativity) Newtonrsquos absolute space andabsolute time Without the absolute space and timethe rsaquolinear-uniform motionlsaquo cannot be explained

3 he laws fail to describe rsaquopoint masseslsaquo (or particles)when their relative distances are of the order of the deBroglie wavelength

It is a great handicap to understanding modern physicswhena system of laws is used as the basis of a physics course thathas been considered outdated for the last 100 years becauseit suggests a world-view that is unfounded in important re-spects he commercial GPS systemprovides everybody withan experimental falsiucirccation of Newtonrsquos laws he GPS sys-temwould notwork if it did not take into account the generalrelativistic corrections to Newtonrsquos gravitation theory in itsalgorithms Until now each generation of school and uni-versity students has had the problem of needing to replacethe view of the classical physics they learned in the ucircrst yearsby moremodern concepts that contradict what before wereconsidered to be irrevocable laws Building amathematicscourse for example upon foundations that have long beenconsidered untenable would be unthinkable

he developers of theKPCmade it their goal to ease this prob-lem by introducing an alternative representation ofmechan-ics and electrodynamics based upon another basic principlethat is still valid today his basic principle is the conservationofmomentum with its corresponding continuity equationhe question of whether or not this approach is better orworse for students or pupils than the traditional one shouldbe kept separate from that of its conceptional correctness

2




F = G sdot A (1)







Current





3


aM1 M2A1 A0

A2

A3 A4

A6

A5

F2

bA1

F1

A2

A4

A5

A3


x(having the same







4












5















6



E re-
















Electrodynamics

41 Magnetic Charge








7












43 Ether Vacuum



8







5 Compatibility







9


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References




F = G sdot A (1)







Current





3


aM1 M2A1 A0

A2

A3 A4

A6

A5

F2

bA1

F1

A2

A4

A5

A3


x(having the same







4












5















6



E re-
















Electrodynamics

41 Magnetic Charge








7












43 Ether Vacuum



8







5 Compatibility







9


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References


aM1 M2A1 A0

A2

A3 A4

A6

A5

F2

bA1

F1

A2

A4

A5

A3


x(having the same







4












5















6



E re-
















Electrodynamics

41 Magnetic Charge








7












43 Ether Vacuum



8







5 Compatibility







9


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References












5















6



E re-
















Electrodynamics

41 Magnetic Charge








7












43 Ether Vacuum



8







5 Compatibility







9


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References















6



E re-
















Electrodynamics

41 Magnetic Charge








7












43 Ether Vacuum



8







5 Compatibility







9


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References



E re-
















Electrodynamics

41 Magnetic Charge








7












43 Ether Vacuum



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5 Compatibility







9


education






7 Addendum











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Summary











Magnetic Charge


Ether Vacuum

Compatibility



References












43 Ether Vacuum



8







5 Compatibility







9


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References







5 Compatibility







9


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References


education






7 Addendum











10




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References




References























3660300107









11






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References






12


Summary











Magnetic Charge


Ether Vacuum

Compatibility



References

statement strunk rincke

Documents