Foucault dissipation in a rolling cylinder: a webcam quantitative study

Bonanno, A; Bozzo, Giacomo; Camarca, M.; Sapia, P.

doi:10.1088/0143-0807/32/2/015

Cited by 12 publications

(21 citation statements)

References 18 publications

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“…Recently, the advent of inexpensive digital cameras has led to a new way for conveying science via image and video demonstrations. If properly calibrated, a series of captured images may contain reliable information that illustrates physical phenomena quantitatively [6], for instance, the measurement of terminal velocity of falling objects [7], the study of Newton's ring [8], Brownian motion [9], and the investigation of Foucault dissipation in a rolling cylinder [10]. In this work, we propose to utilize a wave tray jointly with a digital camera to explore water waves satisfying the deep water condition (h/ Ͼ Ͼ 1) and greatly being dominated by its surface tension.…”

Section: Introductionmentioning

confidence: 99%

Imaging surface water waves for the determination of surface tension and spatial attenuation

Eadkhong

Danworaphong

2014

Can. J. Phys.

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We propose the use of the image analysis technique to determine the surface tension of water and the attenuation coefficients of surface water waves in terms of frequency. Tap water from two different locations is used in our experiments. Water waves are continuously generated at various frequencies in a ripple tank by a plastic blade driven by a function generator. Images of the water waves are then captured by a digital camera and analyzed by using Tracker. As a result, we obtain the surface tension of water at 25°C from both locations that are in good agreement with those resulting from the capillary rise technique. In addition, a linear relationship between the attenuation coefficient of the water waves and driven frequencies, ranging from 40 to 90 Hz, can be observed. Our results indicate that the greater the surface tension the longer distance the water wave takes before its amplitude decreases to 1/e of its original value. This work brings forward a relatively simple technique that can be applied to determine the surface tension and attenuation coefficients of surface water waves in a ripple tank with notable results. PACS Nos.: 47.80.-J, 92.40.Qk, 68.03.Cd. Résumé : Nous proposons une technique d'analyse d'image pour déterminer la tension superficielle de l'eau et le coefficient d'atténuation des vaguelettes de surface en fonction de la fréquence. Nous utilisons ici de l'eau du robinet provenant de deux lieux différents. Les ondes sont générées continuellement à différentes fréquences dans un réservoir d'ondulation à l'aide d'une bande de plastique actionnée par un générateur de fonction. Des images des vaguelettes sont captées par une caméra numérique et analysées par le logiciel Tracker. Nous en tirons des valeurs de tension superficielle à 25°C pour les deux échantillons d'eau, qui sont en bon accord avec les résultats obtenus de la technique de l'effet capillaire. Nous observons aussi une relation linéaire pour le coefficient d'atténuation en fonction de la fréquence entre 40 et 90 Hz. Nos résultats indiquent que plus la tension superficielle est élevée, plus loin voyagent les vaguelettes, avant que leur amplitude soit réduite à 1/e de leur valeur initiale. Ce travail propose une technique relativement simple, utilisable pour obtenir de bonnes valeurs de tension superficielle et du coefficient d'atténuation des vaguelettes. [Traduit par la Rédaction]

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Section: Introductionmentioning

confidence: 99%

Imaging surface water waves for the determination of surface tension and spatial attenuation

Eadkhong

Danworaphong

2014

Can. J. Phys.

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“…In fact, in a type II superconductor, in correspondence of a sufficiently strong local magnetic field, there can be regions in which (as recalled at the end of paragraph 3.2) the magnetic field penetrates, the superconductivity is quenched and the material goes back to the 'normal state'. However, for our specific type II superconductor there is no Foucault dissipation [30] in the (mixed state) bulk: obviously not in the superconducting phase, nor in the normal phase, since the 'bisko' superconductor is ceramic and so its normal phase is insulating. Likely, the missed energy could be stored as field energy, in the magnetic field presumably remnant after the PM passage, due to possible supercurrents remaining in the SC.…”

Section: Discussion and Pedagogical Remarksmentioning

confidence: 90%

“…In fact, the greater is the coil radius (red circle), the bigger is the number of field lines that extend between magnet's poles without concatenation with the coil (green lines in the figure). See [33], p 817.…”

Section: Discussionmentioning

confidence: 99%

“…As known, in this case the braking force on the magnet arises from eddy (or Foucault) currents circulating in the pipe bulk, due to the electromotive force (e.m.f.) induced in it by the time variation of the magnetic field flux [25,27,29,30]. Nevertheless, besides similarities, there are some noticeable differences between the two cases (i.e., the magnet falling through a conventional conductor pipe or through a superconducting one).…”

Section: Introduction and Pedagogical Contextmentioning

confidence: 99%

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An innovative experiment on superconductivity, based on video analysis and non-expensive data acquisition

et al. 2015

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In this paper we present a new experiment on superconductivity, designed for university undergraduate students, based on the high-speed video analysis of a magnet falling through a ceramic superconducting cylinder (T c = 110 K). The use of an Atwood's machine allows us to vary the magnet's speed and acceleration during its interaction with the superconductor. In this way, we highlight the existence of two interaction regimes: for low crossing energy, the magnet is levitated by the superconductor after a transient oscillatory damping; for higher crossing energy, the magnet passes through the superconducting cylinder. The use of a commercial-grade high speed imaging system, together with video analysis performed using the Tracker software, allows us to attain a good precision in space and time measurements. Four sensing coils, mounted inside and outside the superconducting cylinder, allow us to study the magnetic flux variations in connection with the magnet's passage through the superconductor, permitting us to shed light on a didactically relevant topic as the behaviour of magnetic field lines in the presence of a superconductor. The critical discussion of experimental data allows undergraduate university students to grasp useful insights on the basic phenomenology of superconductivity as well as on relevant conceptual topics such as the difference between the Meissner effect and the Faraday-like 'perfect' induction.

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“…Many researches in last decades has shown how experimental activities are significant sources of knowledge in the physics teaching/learning practice, since they offer students the chance to contextualize abstract concepts and to challenge their naïve beliefs [1][2][3].In the case of electromagnetic phenomena, the main difficulties encountered by learners are clearly identified in the literature [4][5][6][7] and in recent years several studies were published focusing on experimental activities as a means to enhance students' conceptual understanding [8][9][10][11][12][13][14][15]. Authors have proposed in the past a number of experiments on the magnetic interaction between permanent magnets; e.g.…”

Section: Introductionmentioning

confidence: 99%

Experiments and models about the force between permanent magnets: asymptotic analysis of a difficult problem

Onorato

Malgieri

2020

Eur. J. Phys.

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We propose a simple experiment which allows students to explore quantitatively the magnetic interaction between neodymium cylindrical magnets. The experiment employs a precision digital balance, two screws with known thread pitch and two transparent tubes to measure the repulsive force between two magnets as a function of their distance. Different measurements are performed, focusing on the behaviour of the interaction force at short and large distances and the role of the magnets' aspect ratio. We discuss the comparison between theoretical expectations resulting from conceptually simple approximate models and experimental results. The experiments employ inexpensive materials and address a relevant topic in the physics curriculum; thus, they are appropriate for the undergraduate physics laboratory, for advanced high school students, and in the context of teacher education and in-service training to enhance students' knowledge of magnetism.

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Foucault dissipation in a rolling cylinder: a webcam quantitative study

Cited by 12 publications

References 18 publications

Imaging surface water waves for the determination of surface tension and spatial attenuation

Imaging surface water waves for the determination of surface tension and spatial attenuation

An innovative experiment on superconductivity, based on video analysis and non-expensive data acquisition

Experiments and models about the force between permanent magnets: asymptotic analysis of a difficult problem

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