Ampere, Electrodynamics, and Experimental Evidence

Hofmann, James R.

doi:10.1086/368661

Cited by 12 publications

(7 citation statements)

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“…Since this transient effect has not been reported, it is clear that the experimenters did not "actually observed the phenomenon", thus leaving no doubt that they completely missed the discovery of electromagnetic induction. For detailed discussions of Amperè's 'induction' experiment see, for instance, [28,30,31,32]. Therefore, it is not surprising that, after the discovery of electromagnetic induction by Faraday in 1831, Amperè's attempt to vindicate the discovery failed.…”

Section: Electromagnetic Induction: An Unseen Guest In the Laboratori...mentioning

confidence: 99%

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Electromagnetic induction: physics, historical breakthroughs, epistemological issues and textbooks

Giuliani¹

2021

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The discovery of Electromagnetism by Ørsted (1820) initiated an "extraordinary decennium" ended by the discovery of electromagnetic induction by Faraday (1831). During this decennium, in several experiments, the electromagnetic induction was there, but it was not seen or recognized. In 1873, James Clerk Maxwell, within a Lagrangian description of electric currents, wrote down a 'general law of electromagnetic induction' given by, in modern form and with standard symbols:In Maxwell's derivation, the velocity appearing in this equation, is the velocity of the line element dl. A modern reformulation of Maxwell's general law, starts with the definition of the induced emf as the• dl, where v c is the velocity of the charge. It is shown that, this apparently minor difference, is fundamental. The general law is a local law: it correlates what happens in the line at the instant t to the values of quantities at the points of the line at the same instant t. For rigid circuits, it is Lorentz invariant. If expressed in terms of the magnetic field, it allows -in the approximation of low velocities -the derivation of the "flux rule", for filiform circuits.The "flux rule" is a calculation tool and not a physical law because it not always yields the correct prediction, it does not say where the induced emf is localized, it requires ad hoc choices of the integration paths and -last but not least -because, if physically interpreted, it implies physical interactions with speeds higher than that of light. Maxwell's general law has been rapidly forgotten; instead, the "flux rule" has deeply taken root. The reasons appear to be various. One is plausibly related to the idea that the vector potential does not have physical meaning, a stand clearly assumed by Hertz and Heaviside at the end of the Nineteenth century. An analysis of university textbooks, spanned over one century, assumed to be representative on the basis of the authors and/or on their popularity or diffusion, suggests that other reasons are related to the habit of presenting electromagnetic phenomena following the historical development and to the epistemological stand according to which physical laws must be derived from experiment without the need of recurring, soon or later, to an axiomatic presentation of the matter. On the other hand, the rooting of the "flux rule" has been certainly favored by its calculation utility: this practical feature has overshadowed its predictive and epistemological weakness.

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Section: Electromagnetic Induction: An Unseen Guest In the Laboratori...mentioning

confidence: 99%

“…coming from the second term of the correct definition of induced emf (28). If we add this term, equation (47) transforms into the correct one (38) or in its approximation for low velocities (36).…”

Section: The Basic Importance Of a Correct Definition Of The Induced Emfmentioning

confidence: 99%

Electromagnetic induction: physics, historical breakthroughs, epistemological issues and textbooks

Giuliani¹

2021

Preprint

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“…como ejemplo podemos mencionar que André-Marie Ampère diseño un programa de investigación que tenía como objetivo detectar corrientes que suponía se iban a inducir en un circuito secundario a partir de una corriente estacionaria introducida en un circuito primario (Hofmann 1987 Dori et al 2007). …”

Section: Implicaciones Para La Enseñanza De La Inducción Electromagnéunclassified

Revisión de la investigación acerca de las ideas de los estudiantes sobre la interpretación de los fenómenos de inducción electromagnética.

Zuza¹,

García²,

Guisasola³

2012

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La teoría de la Inducción Electromagnética (IE) es fundamental en el programa de físicade Secundaria (16-18 años) y cursos introductorios en la Universidad. No es de extrañar que esta teoría yla ley de Faraday constituyan un capítulo específico en los diferentes currículos españoles e internacionales.Sin embargo, aunque la Fuerza de Lorentz y la ley de Faraday son temas comunes en la enseñanza de la IE desde hace muchos años, son recientes los trabajos que se ocupan del aprendizaje logrado por los estudiantes en este tema. En este trabajo se examinan diferentes trabajos sobre concepciones alternativas de losestudiantes de últimos cursos de Secundaria y universidad respecto a la IE y la ley de Faraday. De acuerdo con nuestro análisis, la enseñanza habitual produce poco aprendizaje en las ideas claves de la teoría científica sobre la IE en la física clásica. En general, los diferentes estudios analizados muestran que la mayoría de losestudiantes no tienen una comprensión de un modelo de la IE, ni de la ley de Faraday. Un número significativo de estudiantes no explica los fenómenos sino que los describe o recurre a conocimientos memorísticos presentados de forma incoherente. Otra parte significativa de estudiantes desconoce las causas asociadas ala IE, atribuyéndolas al campo magnético estacionario o a la corriente eléctrica.

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“…What inductivism requires is not the rejection 10. For more on Ampère's electrodynamic theory, see Williams (1965), Hoffman (1987Hoffman ( , 1996, and Steinle (2002a). of all hypothetical speculation but the rejection of an unconstrained method of hypothesis in which one's speculative proposals are not properly tethered to phenomena they purport to explain.…”

Section: The Preliminary Discourse and A Question Aboutmentioning

confidence: 99%