Student interpretations of electric and magnetic fields and forces on the CSEM

This study was undertaken to investigate the construct validity of ten purposefully selected items from the Conceptual Survey of Electricity and Magnetism (CSEM) (Maloney, O'Kuma, Hieggelke, & VanHeuvelen, 2001) and to probe into the mental models used by a group of post-instruction college physics students to answer the questions. The construct investigated was conceptual understanding of electric and magnetic fields and forces. The selected items assessed these topics. The investigation asked in particular if after instruction, would students choose the correct answer on these items on the multiple-choice instrument for scientifically correct reasons.; The results indicate that there are some doubts as to the construct validity of some of the selected items. On each item some students chose the correct answer for reasons that were not classified as scientifically correct. Of the 1120 responses, 7.6% were classified as correct answer choice for wrong reason. Therefore, the fact that the students chose the correct answer did not necessarily mean that they had a correct conceptual understanding of the topic in question. Suggestions for addressing these issues include rewording some of the items as well as restructuring some of the items.; It was also found that students seemed to use one very simple mental model to answer many of the items. The simple model "likes repel and unlikes attract" seems to be used in a universal manner across electric and magnetic domains even when its use is completely inappropriate. It is noted that rewording items on the CSEM will not alleviate this problem. The issue needs to be addressed in the classroom. The data supported previous research that found that in general students do not differentiate between electric and magnetic fields and forces.; As an assessment of conceptual understanding the CSEM is a step in the right direction. Once the instrument has been revised to address the issue of construct validity of some of the items, it would be beneficial to compare results on the instrument of different classes using different curricula.