Microscopic models for bridging electrostatics and currents

A teaching sequence based on the use of microscopic models to link electrostatic phenomena with direct currents is presented. The sequence, devoted to high school students, has been designed after an initial work carried out with student teachers attending, at the University of Pavia, the School of Specialization for teaching Physics in high school. The results obtained are briefly presented because they oriented our steps for the development of the teaching sequence. For both the design of the experiments and their interpretation we drew inspiration from the original works of Alessandro Volta; in addition, a structural model based on the particular role of electrons as elementary charges both in electrostatic phenomena and in currents was proposed. The teaching sequence starts from experiments on charging objects by rubbing and by induction and engages students in constructing microscopic models to interpret their observations. By using these models and by deepening the ideas of tension and capacitance, the students recognize that a charging (or discharging) process is due to moving electrons that, although for short time intervals, represent a current. Finally, they see that the same happens in transients of direct urrent circuits