A low-cost smartphone-connected electroscope

When teaching electrostatics, it is often difficult to convey that electric charge is an abstract concept because it is invisible to the naked eye. Although traditional plate electroscopes react visibly to the presence of charges, they do not provide clear feedback regarding the sign or exact quantity of the charge, which makes it difficult for students to understand the phenomena. In our article, we aim to fill this gap by presenting the design and operation of a charge meter device developed in-house, as well as various possibilities for its use in education. Our device is not only capable of detecting the presence and sign of charges but is also innovative in that it indicates the magnitude of the electric field of a nearby body, which is proportional to the amount of charge. To encourage our colleagues to follow our example, we discuss in detail the selection of the units used in the development and the steps of the application. Additionally, we present five selected experiments in detail that can be performed with the device. From student feedback we conclude a great potential to foster conceptional understanding of electrostatic phenomena and to enhance students' motivation.