Hand- and Minds-on Electricity and Magnetism II

The paper consists of two parts – experiments for students and experiments for teachers. First part contains two experiments, which were found in literature or internet, verified and quantitatively measured. The second part concerns about two workshops for physics teachers. Introduction There are many experiments from the area of electricity and magnetism, but quite often these experiments are presented only qualitatively. Following on my article in WDS last year ([4]), I'd measured some of experiments I described last year. Results of my measurements are in first part of the article named “Experiments for students”. One of goals of my work is experiments for teachers and experiments, which they can do with their students. So, the second part of the article named “experiments for teachers“ consists of information about two workshops for physics teachers. Experiments for students Demonstrating diamagnetism The original experiment is described in the article “Demonstrating diamagnetism” [1]. It shows how to demonstrate diamagnetic force between bismuth sample and a magnet. The experimental setup is shown at fig. 1. It contains sensitive electronic balance, nonmagnetic stand, bismuth sample and neodymium magnet. When the magnet is near the bismuth sample, the electronic balance registers positive “mass” – the diamagnetic force. In our arrangement the electronic balance was sensitive to a centigrams, the stand was from plastic cup and paper roll (it must be at least 25 cm high). We have bismuth in the form of small scales in a plastic box. The weight of our bismuth sample was about 100 grams. The distance between the bismuth and the magnet is about few millimetres. In our arrangement the “mass” was about few centigrams, corresponding to diamagnetic force about few tenths of milinewtons. This experiment may be useful in schools, where sensitive electronic balance are available. Instead of bismuth it is possible to use diamagnetic carbon. How big is the force between a tin and a straw? Motivation of this experiment comes from videos on YouTube. There are many videos with tins rolled on a table and powered by charged poles (see for example [2]). These experiments are only qualitative. But a natural question may arise, which can give the motivation for example for a student project: How big is the force between the tin and the charged straw (or the pole). Figure 1. The arrangement of the experiment “Demonstrating diamagnetism.” 258 WDS'09 Proceedings of Contributed Papers, Part III, 258–262, 2009. ISBN 978-80-7378-103-3 © MATFYZPRESS