The study of the transient regime in electric circuits with Excel spreadsheets

摘要

This paper focuses on the use of Excel spreadsheets in the study of thetransient regime in electric circuits. Two relevant didactic tools, which have beencreated with the help of spreadsheets, are presented for the study of the transientregime in a circuit with resistance and capacitance connected in series. With the aid ofthe first tool we can simulate the charging and discharging of a capacitor. Bychanging the input data we can easily track how the charging and, respectively, thedischarging curves change for the electric charge of the capacitor, the voltage acrossthe capacitor and the current through the circuit. The significance of the time constantfor the RC circuit is emphasized in graphs. The energetic characterization of thetransient regime is done through a graph presenting the energy variation in time, fromthe capacitor, and the energy dissipated in the resistor. For a comparative analysis agraph is drawn, overlaying the curves of the time dependence in case of the capacitorvoltage from three different RC circuits. The second tool has been conceived toprocess the data in the didactic experiment to study the process of discharging of acapacitor on a resistor. The voltage on the capacitor terminals measured during thedischarging process is compared to the voltage calculated with the exponentialvariation law of the process. From the discharging curve we can determine thecapacitance of the capacitor and, thus, certain experimental results are presented. Thetwo previously described tools prove the facilities offered by spreadsheets inconceiving interactive Physics lessons. On the one hand, the possibility to simulatesome physical phenomena is highlighted; on the other hand, it is shown thatspreadsheets can be successfully used in the processing of experimental data.