Using a PC and external media to quantitatively investigate electromagneticinduction

Abstract

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