Mobilization of the magnetic field concept by students from DEUG "Sciences de la Matière": didactic analyze using the conceptual fields theory.
Using the “theory of the conceptual fields” (Vergnaud, 1990), this research in didactics of physics science, reveals the dynamics of the cognitive patterns of undergraduate students (issus d’un DEUG "Sciences de la Matière"). The investigation consists in collecting data during “problem-solving situations” in electromagnetism, when students have to use the concept of magnetic field. After an exploratory study with the aim to identify the reccurent difficulties encountered by students when they mobilize concepts in electromagnetism, we sought to identify “operational invariants” and “schemes” used by students to solve these situations.
The study shows that students :
use “ready-to-use” invariants, invariants whose “signified in physics” are not specified and “not contextualized” invariants to the “problem-solving situations” ;use a very few “operational invariants” which belong to the university curriculum in electromagnetism ;meet enormous difficulties with the understanding of the concept of magnetic field and its relationship with the electric field in variable mode ; andoperational invariants juxtaposed or combined without control of their relevance during the processes reasoning.
These difficulties are :
linked to the student’s relationship to the physics knowledge, in particular an utilitarian relationship ;caused by a “dysfunctioning” of the processes of reasoning (with one of the three levels of organization of higher faculties as pointed out by Kant);bounded with a lack of control and search for “signified in physics” during the academic work;linked to the abstracted nature of the concerned knowledge ; and finallyin certain cases, could be linked with epistemological obstacles.Following these interpretations, directions for future researchs should be to study in depth the student’s reasoning including other fields than electromagnetism, as well as to carry on studies to implement solutions regarding the noted "dysfunctions". This supposes a close cooperation between didacticians and specialists in cognitive sciences.
Key words: didactics of physics, electromagnetism, operational invariants, scheme, magnetic field, theory of the conceptual fields.
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