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Many students in physics courses fail to achieve a desired conceptual change because they assign an incorrect ontology to the to-be-learned concept. This situation has been detected in previous research for the case of field lines: many college students assign material properties to the lines and describe them, for example, as tubes that contain or transport charges. The historical evolution of this concept shows that early scientists like Faraday assigned material properties to these lines in some occasions. In the present work a history-based instructional material was designed to foster the analysis of the ontology of field lines to help students at an Argentinean university achieve conceptual change. The predicates used by the students to describe physical situations were used as evidence of the assigned ontological status. Conceptual change was measured by the change in the proportion of geometrical predicates that students used when referring to the lines in a written questionnaire. This change was significantly higher for the students learning with the history-based material compared to those that learned in the regular class. Some characteristics of the material and geometrical ideas that students hold about the field lines were determined through an oral interview.

In this work we analyzed how electric and magnetic lines of force were conceived by Faraday and how they are understood by a group of Argentine university students after receiving instruction. Our results show that many students possess ideas similar to those of Faraday in that lines of force are conceived as real physical entities responsible for the transmission of the electric action. These results are in accordance with the interpretation of physical entities as ``matter-based'' suggested by Chi et al. (1994). It is suggested that emphasis on the geometrical character of these lines seems imperative in basic electromagnetism classes in order to avoid this kind of confusion. [ABSTRACT FROM AUTHOR]