Laurence Viennot

Spontaneous Reasoning in Elementary Dynamics

Summaries English The scope of this study was to explore and analyse spontaneous reasoning of students in elementary dynamics, from the last year at secondary school to the third year at University. A set of investigations involving several hundred students (mainly French, but also British and Belgian) showed surprising rates of wrong, or right, answers, which are very stable from one sample of students to another. It seems difficult to attribute these results solely to school learning. But they can be reasonably well accounted for if we assume a spontaneous explanatory system, relatively unaffected by school learning. In particular, students seem to use in their reasoning two different notions of dynamics, usually designated by the same word: ‘force’. To detect which of these two notions has, in fact, been used, one must look at their properties: one of these ‘forces’ is associated with the velocity of a motion whilst the other one is associated with its acceleration. Likewise, the part played by energy ...

Students’ reasonings in thermodynamics

Some tendencies in common reasoning aim at reducing the complexity of multi‐variable problems. Two main aspects of these tendencies are illustrated here with results of an investigation of students about thermodynamics: 1. 1. A physical quantity which depends on several others may be treated as if it were depending on only one. Such a reduction of the number of variables may also be obtained by combining two of them, as if they were two facets of the same variable. For example, mean distance between particles and mean speed are treated as equivalent aspects of thermal motion. This results in a linear shape of argument φ1 ®φ2 ®φ3 ®…, where each phenomenon φn evoked is specified with only one physical quantity 2. 2. Some apparent contradictions in students’ responses may be understood if one admits that there is a chronological connotation in the argument: an arrow, ‘®’, or a ‘then’, means not only ‘therefore’, but also ‘later’ The pedagogical implications of the findings are discussed, mainly in relation t...

Reading images in optics: Students' difficulties and teachers' views

This paper focuses on difficulties students have in reading images, regarding the understanding of a particular domain, e.g. optics and colour. We concentrated upon what extent teachers were conscious of such difficulties and what they suggested doing to avoid possible pitfalls in this respect. A list of expected obstacles, set up to initiate the study, was shown to be appropriate. It shows that, when they predicted or observed a misunderstanding, the consulted teachers tended to add some elements to a misleading image rather than discussing the symbols that were used, their more or less realistic status and their possible ambiguity. Implications for teacher training and the design of innovative sequences are briefly discussed.

Students’ reasoning about the superposition of electric fields

This study concerns students’ ideas about the superposition of electric fields. Two paper‐and‐pencil questionnaires were given to university students to investigate possible obstacles to a correct use of this principle. The results confirm an expected difficulty about Gausss theorem, i.e., the idea that only ‘internal’ charges create a field on a given closed surface. Another more surprising finding is that students are reluctant to admit that a field can penetrate into, or go out of, an insulator, particularly because ‘charges cannot move’. These first findings are discussed in connection with common features of students’ reasoning about mechanics and about multivariable problems. Some directions of future research are proposed.

Using models at the mesoscopic scale in teaching physics: two experimental interventions in solid friction and fluid statics

This article examines the didactic suitability of introducing models at an intermediate (i.e. mesoscopic) scale in teaching certain subjects, at an early stage. The design and evaluation of two short sequences based on this rationale will be outlined: one bears on propulsion by solid friction, the other on fluid statics in the presence of gravity. Both concern students in the first university year and were designed with common conceptions of students on these topics as a guide. The common points and the differences of the two sequences are discussed, and particularly the characteristics of the mesoscopic approach. The evaluation is made by analysing the recordings of class discussions and comparing the results of control groups via written questionnaires. Teachers reactions have also been documented. These elements show that the proposed mesoscopic models encourage a more articulated reasoning on the physical situation, helping students to reconcile a global description with the analysis of local interactions.

Transformation of didactic intentions by teachers : the case of geometrical optics in grade 8

This investigation is based on the following idea: as regards the implementation of research based innovations, teachers are not passive transmitters, and some general trends can be found in the way they transform the proposed strategies. This paper deals with the particular case of elementary optics in grade 8 in France, a syllabus launched at national level in 1993. Four sets of data - interviews before teaching, logbooks, assessment tasks and video recorded class observations - lead to converging conclusions. These suggest the interest of extending such research to other topics and provide some hints on how to design innovations with maximized chances of appropriate implementation by teachers.

Can we Evaluate the Impact of a Critical Detail? The Role of a Type of Diagram in Understanding Optical Imaging

This paper describes an attempt at evaluating a potentially critical “detail” of teaching practice; that is, using a particular diagram to illustrate the imaging role of a converging lens. This “basic” diagram has been designed to contribute to help students overcome the well‐known “travelling image” syndrome. We conducted a comparative study with 125 students in all, at three academic levels: end of secondary school, degree students, and teacher training. The groups compared had previously been taught elementary optical imaging in a classical, uncontrolled manner, and were presented with two classical questions, commonly used to demonstrate students’ difficulties. In each group, one‐half of the students had a classic introductory diagram and the other half had the “basic” one. A positive reaction of students to the evaluated diagram was observed at a relatively high academic level (trainee physics teachers and degree students), in contrast with an apparent lack of effect at the end of secondary school. The paper ends with a discussion of the evaluation of a detail of practice in isolation, with respect to the distance between students’ actual and targeted levels of comprehension.

Mapping Gravitational and Magnetic Fields with Children 9–11: Relevance, difficulties and prospects

This paper presents an investigation centered on a guided conceptual path concerning magnetic and gravitational fields, proposed for children aged 9–11. The goal is to appreciate to what extent the idea of “mapping” two fields of interaction is accessible and fruitful for children of that age. The conceptual target is to link magnetic and gravitational sources with their respective field lines, and then use this linkage to differentiate between the two kinds of interactions. This study shows that the proposed “mapping” and the differences between the maps are accessible to a large proportion of pupils. By contrast, only a minority can differentiate between the two types of interactions: the idea of mere attraction remains dominant and may screen the idea of orientation. Finally, we discuss to what extent these exploratory results confirm the relevancy of such teaching goals and how they inform the design of research‐based teaching sequences concerning this topic.

Two dimensions to characterize research‐based teaching strategies: examples in elementary optics

This article deals with the following question: how can research in science education enrich the design of teaching innovations? Two possible answers are examined: Students’ own ways of reasoning may be taken into account, either as provisional steps towards more elaborate views or as obstacles to be confronted. The epistemological framework of episodes using an experimental set‐up may be used. This can take different forms, ranging from simple inductions to searches for consistency between given laws or hypotheses and experimental facts. The new French curriculum provides two examples of strategies concerning elementary optics at grade 8 that can be analysed along these lines. The value of these strategies is discussed. Different combinations of the role of learners’ previous ideas and epistemological aspects are also examined. Some elements of evaluation concerning one of the recommended combinations are given. Finally, the role of teachers as ‘innovation transformers’ is presented as a critical topic f...

A Mesoscopic Model of Liquids for Teaching Fluid Statics

After a study on students’ conceptions concerning pressure in fluids, we elaborated a short teaching sequence on the statics of liquids, implemented and evaluated for two years among science students in the first university year. The sequence makes use of a model of liquids at the mesoscopic level through an analogy with a set of sponge balls, treated first as mechanical entities, then as a model of elements of fluids. The aims and the results of this experimentation are presented and discussed.