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See discussions, stats, and author profiles for this publication at:Testing theoretical models of magnetic damping using an air trackArticleinEuropean Journal of Physics · February 2007DOI: 10.1088/0143-0807/29/2/014 · Source: arXivCITATIONS14READS8714 authors, including:Some of the authors of this publication are also working on these related projects:Flip teachingView projectAna VidaurreUniversitat Politècnica de València82PUBLICATIONS1,104CITATIONSSEE PROFILEMarcos H. GiménezUniversitat Politècnica de València50PUBLICATIONS241CITATIONSSEE PROFILEAll content following this page was uploaded byAna Vidaurreon 13 December 2012.The user has requested enhancement of the downloaded file.
1Testing theoretical models of magnetic dampingusing an air trackAna Vidaurre, Jaime Riera, Juan A. Monsoriu, and Marcos H. GiménezDepartment of Applied Physics, Polytechnic University of Valencia, E-46022 Valencia,SpainABSTRACTMagnetic braking is a long-established application of Lenz’s law. A rigorousanalysis of the laws governing this problem involves solving Maxwell’s equations in atime-dependent situation. Approximate models have been developed to describe differentexperiences related to this phenomenon. In this paper we present a new method for theanalysis of the magnetic braking using a magnet fixed to the glider of an air track. Theforces acting on the glider, a result of the eddy currents, can be easily observed andmeasured. As a consequence of the air track inclination, the glider accelerates at thebeginning, although it asymptotically tends towards a uniform rectilinear movementcharacterized by a terminal speed. This speed depends on the interaction between themagnetic field and the conductivity properties of the air track. Compared with previousrelated approaches, in our experimental setup the magnet fixed to the glider produces amagnetic braking force which acts continuously, rather than over a short period of time.The experimental results satisfactorily concur with the theoretical models adapted to thisconfiguration.E-mail:[email protected]
2I. INTRODUCTIONWhen a conductor material is under the effect of a changing magnetic flux, eddycurrents are induced in the conductor. This change in the flux can be produced eitherbecause the conductor is moving in a region where there is a magnetic flux or, similarly,because the magnet is moving. The action of the magnetic field on the induced currentsproduces a braking force. A rigorous analysis of the laws governing the problem entailsthe solving of the Maxwell equations in a time-dependent situation. This depends on theproblem geometry and it is usually difficult to solve.Widerick et al.1present a very simple model for the calculation of the magneticdrag force on a moving metal disc in the air gap between the rectangular-shaped polepieces of an electromagnet. Likewise, Cadwell2analyzes the effect of magnetic dampingon an aluminium plate moving on a horizontal air track as it passes between the poles of ahorseshoe magnet. In both cases, it is assumed that the induced current in the “shadow”of the magnet is uniform and equal to)(BvJ×σ=. Both papers present a simple modeland fail when trying to explain the influence of the magnet size or its position withrespect to the motion direction. Heald3replaces the simplification of considering the eddy

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Term
Fall
Professor
mr. wagrd
Tags
Magnetic Field

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