The incandescent bulb has been a useful tool for teaching basic electrical circuits, as brightness is related to the current or power flowing through a bulb. This has led to the development of qualitative pedagogical treatments for examining resistive combinations in simple circuits using bulbs and batteries, which were first introduced by James Evans and thoroughly expanded upon by McDermott and others. This paper argues that replacing bulbs with small computer fans leads to similar, if not greater, insight of experimental results that can be qualitatively observed using a variety of senses. The magnitude of current through a fan is related to the frequency of the rotating fan blades, which can be seen, heard, and felt by the students. Experiments using incandescent bulbs only utilize vision, which is not ideal as the human eyes’ perception of brightness is skewed because the response to light intensity is logarithmic rather than linear.
Teaching simple circuits and Ohm’s law to students in the introductory classroom has been extensively investigated through the common practice of using incandescent light bulbs to help students develop a conceptual foundation before moving on to quantitative analysis. However, the bulb filaments’ resistance has a large temperature dependence, which makes them less suitable as a tool for quantitative analysis. Some instructors show that light bulbs do not obey Ohm’s law either outright or through inquiry-based laboratory experiments. Others avoid the subject altogether by using bulbs strictly for qualitative purposes and then later switching to resistors for a numerical analysis, or by changing the operating conditions of the bulb so that it is “barely” glowing. It seems incongruous to develop a conceptual basis for the behavior of simple circuits using bulbs only to later reveal that they do not follow Ohm’s law. Recently, small computer fans were proposed as a suitable replacement of bulbs for qualitative analysis of simple circuits where the current is related to the rotational speed of the fans. In this contribution, we demonstrate that fans can also be used for quantitative measurements and provide suggestions for successful classroom implementation.
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