A FAN-C Exploration of RC Circuits

Recently, small computer fans have been demonstrated to be an effective method for teaching simple resistive circuits both qualitatively and quantitatively. The current through the fans is related to the rotational speed of the fans and allows multiple senses to be engaged (touch, sight, and hearing). Methods for learning simple circuits in an effective and accessible way have been explored for decades, and the prevailing approach has been the use of incandescent light bulbs. However, light bulbs can only be used to build a qualitative foundation. Quantitative experiments require non-bulb circuits, as the resistance of incandescent light bulbs changes with current. When fans are used, plots of current vs. voltage exhibit a linear relationship, which provides a nearly constant effective resistance for the fan. This suggests that fans can also be used to explore RC circuits both qualitatively and quantitatively, where the fans act as the resistive elements as well as the indicator. In this contribution, we will demonstrate that computer fans can be used to qualitatively explore the charging and discharging times for RC circuits. By monitoring the voltage across the capacitor as a function of time, we will also show that fans can be used for quantitative RC analysis.