“On the Production of Currents and Sparks of Electricity from Magnetism,” <i>American Journal of Science and Arts</i> (July 1832)

Henry, Joseph

doi:10.7135/upo9780857286512.015

Cited by 3 publications

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“…These experiments are usually presented in textbook or classrooms as the starting point for talking about electromagnetic induction. Joseph Henry had obtained some of these results one year before, but published them one year later [39]. Faraday's researches can be considered as an archetype of experimental enquire.…”

Section: Electromagnetic Induction: the Discoverymentioning

confidence: 99%

“…If one takes into account the fact that the length of the solenoid is finite, the magnetic field outside the solenoid is not null. This implies that the value of the vector potential is smaller than that calculated by equation ( 41) and, consequently, the measured emf is smaller than that given by equation (39) [68, pp. 253 -254].…”

Section: Why the "Flux Rule" Is Not A Physical Lawmentioning

confidence: 99%

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

Giuliani¹

2021

Preprint

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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: the Discoverymentioning

confidence: 99%

Section: Why the "Flux Rule" Is Not A Physical Lawmentioning

confidence: 99%

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

Giuliani¹

2021

Preprint

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“…Henry learned of Faraday's accomplishments from a short, one page account published in the Philosophical Magazine for April 1832 [26]. Henry thought he had observed 'electrical effects' in his experiments with electromagnets that were different from but related to Faraday's electromagnetic induction, and he published an account of his observations in July of 1832 [27]. In his own words: 'Before having any knowledge of the method given in the above account (Faraday's Phil.…”

Section: Discovering Mutual Inductionmentioning

confidence: 99%

“…article), I had succeeded in producing electrical effects in the following manner, which differs from that employed by Mr Faraday, and which appears to me to develop some new and interesting facts.' Figure 7 is a schematic drawing for Henry's experiment [5,27]. He used an electromagnet from his earlier experiments, probably the multi-coil magnet shown in figure 3(a) with all nine coils connected in parallel (the primary coil).…”

Section: Discovering Mutual Inductionmentioning

confidence: 99%

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Joseph Henry’s role in the discovery of electromagnetic induction

Smith¹

2016

Eur. J. Phys.

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The discovery of electromagnetic induction in the early part of the 19th century is one of the greatest scientific achievements of all time, and it has had tremendous technological consequences. The credit for this discovery rightfully goes to the great English experimental physicist Michael Faraday. However, the American physicist Joseph Henry made some observations comparable to Faraday’s at nearly the same time, and for that reason, Faraday and Henry are often considered to be co-discoverers of some aspects of electromagnetic induction. We examine Henry’s early research on electromagnetism, starting from his efforts to improve the electromagnet, which led directly to his investigations of induction. We describe his earliest experiments on both mutual and self-induction, and pay particular attention to the relationship of Henry’s research to that of Faraday. The approach is one in which the experiments are described and then analysed using modern theory and terminology.

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Michael Faraday and the Inductionists [Historically Speaking]

Bird

2024

IEEE Antennas Propag. Mag.

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Michael Faraday and the Inductionists Michael Faraday was the first to discover magnetic induction, but there were several others searching for induction effects at the same time and even earlier. This group is referred to as the "inductionists." These included Fresnel, Ampere, and Henry, as well as Faraday. This article outlines the directions each of them took and the interactions Faraday had with them. There was an interesting set of speculations and experiments on the path to discover electromagnetic induction before Faraday's success in 1831.

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“On the Production of Currents and Sparks of Electricity from Magnetism,” American Journal of Science and Arts (July 1832)

Cited by 3 publications

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

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

Joseph Henry’s role in the discovery of electromagnetic induction

Michael Faraday and the Inductionists [Historically Speaking]

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