Understanding key concepts of electric circuits: Students' use of mental models

This study presents an action research project on the teaching and learning of fundamental ideas about electric circuits, gathering data from two cohorts. Students’ ideas were probed using diagnostic test questions asked in pre-tests, post-tests and delayed post-tests. Semi-structured interviews were used with students of different abilities to indicate the mental models that students appeared to be using. Additional teaching activities were introduced with Cohort 1. The effect of these activities was reflected upon, guiding further additions to teaching activities used with Cohort 2. These activities addressed specific points that seemed to pose particular difficulties for students with the aim of improving students’ qualitative understanding through guided reflection and discussion. The performance of Cohort 2 was significantly weaker at the pre-test stage but Cohort 2 made better overall progress through the course of study when compared with Cohort 1. Both cohorts made noticeable improvement in their understanding of current conservation. However, problems with parallel circuits and with distinguishing between potential difference (p.d.) and current remained. While p.d. was described by the high ability students in terms of forces between negative charges and the battery terminals, no student referred to the electric field which exists between battery terminals even in open circuit. In attempting to understand the behaviour of electric circuits, students appear first to construct a mental model of electric current. The data collected suggest that students start to understand p.d. when they ‘see’ it as some kind of difference between points. The data also suggest that the scientific model of p.d. is more difficult to visualise and use, putting p.d. at a higher level than current, in a logical hierarchy of ideas. This study proposes a unified learning model for electric circuits, in terms of a possible sequence of intermediate mental models of current, resistance and p.d. leading towards the scientific view. This learning model can help both students and teachers. Students can use it to gauge their level of understanding of circuits and to reflect on what still needs to be understood. Teachers may use the learning model as a tool helping in understanding the difficulties students experience and guiding in what next to teach to improve students’ understanding of electric circuits.