Using a PC and external media to quantitatively investigate electromagnetic induction

Abstract

In this article we describe an experimental learning path about electromagnetic induction which uses an Atwood machine where one of the two hanging bodies is a cylindrical magnet falling through a plexiglass guide, surrounded either by a coil or by a copper pipe. The first configuration (magnet falling across a coil) allows students to quantitatively study the Faraday–Neumann–Lenz law, while the second configuration (falling through a copper pipe) permits learners to investigate the complex phenomena of induction by quantifying the amount of electric power dissipated through the pipe as a result of Foucault eddy currents, when the magnet travels through the pipe. The magnet’s fall acceleration can be set by adjusting the counterweight of the Atwood machine so that both the kinematic quantities associated with it and the electromotive force induced within the coil are continuously and quantitatively monitored (respectively, by a common personal computer (PC) equipped with a webcam and by freely available software that makes it possible to use the audio card to convert the PC into an oscilloscope). Measurements carried out when the various experimental parameters are changed provide a useful framework for a thorough understanding and clarification of the conceptual nodes related to electromagnetic induction. The proposed learning path is under evaluation in various high schools participating in the project ‘Lauree Scientifiche’ promoted by the Italian Department of Education.

Atwood’s Machine and Electromagnetic Induction: A Real Quantitative Experiment to Analyze Students’ Ways of Reasoning

“…These tutorials had the dual role of engaging students in a challenging inquiry learning environment and monitoring their learning paths. 6) is collected and analyzed through the Visual Analyser free software (Bonanno et al, 2011).…”

“…Our proposal was designed according with the processes of the Design Based Research (Anderson & Shattuck, 2012;Collins et al, 2004;DBRC, 2003), within the theoretical framework of Model of Educational Reconstruction (Duit et al, 2005) in a vertical perspective (Constantinou, 2010;Méheut & Psillos, 2004;Michelini, 2010). Taking into account the learning difficulties about EMI above discussed and considering educational and disciplinary perspectives of various experiments about these phenomena (Fodor & Peppard, 2012;Ivanov, 2000;Kingman et al, 2002;Layton & Simon, 1998;MacLatchy et al, 1993;Ochoa et al, 1998;Roy et al, 2007;Sawicki, 2000;Trumper & Gelbman, 2000), we decided to introduce EMI (i) starting from a sequence of qualitative experimental explorations based on the IBL operative approach (Abd-El-Khalick et al, 2004;Heron et al, 2004;McDermott, 1991;McDermott & Shaffer, 1998) and then (ii) constructing quantitative basis for the comprehension of FNL law through Real-Time experiments (Bonanno et al, 2011;Priest & Wade, 1992;Ivanov, 2000;Kingman et al, 2002;Sokoloff et al, 2007;Huang et al, 2008;Fodor & Peppard, 2012;Michelini & Vercellati, 2014a). Our educational approach is based on an empirical introduction of the magnetic field concept, as a property of the space around a magnet (Michelini & Viola, 2008, 2009, 2010 and represented through the model of field lines (Michelini & Vercellati, 2012, 2014b.…”

“…The IBL strategy adopted in our approach was integrated with a problem-solving activity, in which students applied the conceptual understanding developed in previous step (i.e., the magnetic field and its representation) to construct both the concept of magnetic flux and the idea of its time variation (Guisasola et al, 2008;Michelini & Vercellati, 2014b). The quantitative experiments performed using online sensors offered students opportunities to analyze the central role of time variation of magnetic field flux in EMI phenomena (Bonanno et al, 2011;Michelini, 2006Michelini, , 2018.…”

“…We used an existing experimental setup (Bonanno et al, 2011) to perform quantitative measures of EMF induced by a magnet falling across a coil (see Figure 3). This Atwood's machine (hereafter electromagnetic Atwood's machine or EM Atwood's machine) allowed students to follow the magnet motion also when it was inside the coil.…”

Approximate and Proper Electromagnetic Modelling in Moving Conductors

“…In the air-filled regions inside and outside the tube, σ = 0 is set in (5). A φ is continuous at the boundaries and vanishes at infinity.…”