Teaching the basics of electricity using a flexible piezoelectric generator

Abstract

Lecturer-researchers, because of the duality of their profession, have the opportunity to introduce students directly to their research. Stimulating student interest through practical research topics enables students to see the relevance of the teaching/learning process and thereby enhances their motivation. As a major societal issue, research on renewable energies is held in great esteem, particularly among young students with a strong interest in environmental issues. The work presented here relates to the realization of a practical class on the testing of a flexible piezoelectric generator studied as part of the "N-air-J" regional research project. The particular characteristic of piezoelectric materials is that they produce electricity when compressed, which means that they can be used in energy recovery devices. The electrical model associated with this type of generator, consisting of an ideal current source in parallel with a linear capacitor and a load resistor, is sufficiently simple to be understood by first-year university students following a course on electricity. Using an appropriate mechanical excitation system (made out of Lego©), it is possible to generate variations in the quasi-sinusoidal compressions of a flexible piezoelectric film. By connecting an oscilloscope directly to the terminals of this experimental generator, students can visualize the produced current flowing through its input impedance, thus making it possible to use the laws of electrokinetics on an alternating sinusoidal current. As the objective of the practical class is to calculate the energy density produced by this type of generator, it uses the notions of Ohm's law, current dividers, equivalent resistances (serial/parallel associations), power and density of energy to provide concrete examples of some of the basics of electricity. High school students in year one of a science and laboratory technology baccalaureate in France have already taken this practical class as part of a dissemination campaign on scientific culture.