Probing Student Understanding of Basic Concepts in Introductory Electrical Engineering Courses

We report on an ongoing investigation of student understanding of basic concepts in the context of various first-year undergraduate DC and AC circuits courses. Through analysis of student responses to mostly qualitative quiz and examination questions, we have identified prevalent and persistent difficulties with a number of topics, including equivalent sources and load lines, Kirchhoff’s laws, and the phase relationships between AC signals. For example, between half and two-thirds of the students expected a phase difference to occur between the voltage of an ideal source and that of a capacitance connected directly across it. Similarly, between 30 % and 40 % of the students expected a phase difference between the currents through a resistance and an inductance connected in series. We interpret these results as an indication of an incomplete understanding of Kirchhoff’s voltage and current laws in the context of AC circuits and note that these difficulties mirror similar misconceptions that have been observed among other student populations in the context of DC circuits. Other difficulties related to phases of AC signals include a presumed equality of phases between the voltage across and the current through an ideal voltage source