June 14, 2015
June 14, 2015
June 17, 2015
Electrical and Computer
26.158.1 - 26.158.15
Addressing Barriers to Learning in Linear Circuit AnalysisIntroductory-level linear circuit analysis is a key gateway course in electrical engineering, and isfrequently studied by many other engineering majors. Yet failure (DEW) rates can average 23%,varying from 3% to 53% depending on individual instructor and section. Student difficultiesmay arise from a variety of causes, such as insufficient mathematical skills, lack of rapidfeedback, insufficient use of active learning strategies, and varying levels of motivation(especially if it is outside their major area). In this paper, we argue that a key and perhapsunrecognized factor is a failure to systematically teach students all of the principles they reallyneed to know to solve circuit problems, and to address typical qualitative misconceptions. Wemeasure conceptual understanding of basic DC electricity concepts using the DIRECT conceptinventory of Engelhardt & Beichner, administered as both a pre-test and a post-test in over 22sections of a linear circuits class involving over 1000 students over two years. Pre-test scores arearound 49% as found by others. Post-test scores typically rise to only 57% (averaged over manyinstructors), showing that conventional instruction does not address qualitativemisunderstandings very effectively. By introducing targeted instruction in one section to addressmisconceptions, the post-test score rose to 68% in Spring 2013 (higher than any other section)and with further refinement reached 77% in Fall 2013 (a large, statistically significant effect sizeof 1.02 standard deviations).Key items we emphasize include a brief presentation of a microscopic Drude model of currentflow to provide a better understanding of current and voltage, and a “ball & tube” model ofconduction to explain the constant nature of current flow at different points in a single loop andthe need for complete circuits. Importantly, we compare and contrast the behavior of current andvoltage sources to dispel the extremely common misconception that batteries are current sources.We model sources with a control loop that constantly adjusts the current of a voltage source (orthe voltage of a current source) to maintain the constant voltage output. This model emphasizesthat one parameter stays constant while the other can vary, and that all sources supply bothcurrent and voltage in general. In solving circuits we introduce the idea of “redundant” sourcesand passive elements that have no effect on the remainder of the circuit (i.e., those in series witha current source or in parallel with a voltage source); and “hinged” circuits, which can be drawnsuch that one or more portions are connected by a single wire, and are therefore effectivelyisolated. We identify “voltage-splittable” circuits (those where voltage sources effectively cutthe circuit into two independent pieces), and “current-splittable” circuits, where current sourcesdo the same. We emphasize accurate understanding of series and parallel connections,particularly when terminals are present (through which current may or may not flow). Byintroducing these and other seldom expressed rules for circuit analysis that we will describe, weshow that students can attain improved conceptual understanding of circuit analysis topics.
Skromme, B. J., & Robinson, D. (2015, June), Addressing Barriers to Learning in Linear Circuit Analysis Paper presented at 2015 ASEE Annual Conference & Exposition, Seattle, Washington. 10.18260/p.23497
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