Students’ reasoning when tackling electric field and potential in explanation of dc resistive circuits

This study examines the causal reasoning that university students use to explain how dc circuits work. We analyze how students use the concepts of electric field and potential difference in their explanatory models of dc circuits, and what kinds of reasoning they use at the macroscopic and microscopic levels in their explanations. This knowledge is essential to help instructors design and implement new teaching approaches that encourage students to articulate the macroscopic and microscopic levels of description. A questionnaire with an emphasis on explanations was used to analyze students’ reasoning. In this analysis of students’ reasoning in the microscopic and macroscopic modeling processes in a dc circuit, we refer to epistemological studies of scientific explanations. We conclude that the student explanations fall into three main categories of reasoning. The vast majority of students employ an explanatory model based on simple or linear causality and on relational reasoning. Moreover, around a third of students use a relational reasoning that relates two magnitudes current and resistance or conductivity of the material, which is included in a macroscopic explanatory model based on Ohm’s law and the conservation of the current. In addition, few students situate the explanations at the microscopic level (charges or electrons) with unidirectional cause-effect reasoning. This study looks at a number of aspects that have been little mentioned in previous research at the university level, about the reasoning types students use when establishing macro-micro relationships and some possible difficulties with complex reasoning.

Figure 1

A simple circuit with a carbon resistor.

Figure 2

The electric field at a point outside the resistor is equal to the electric field at a point inside the resistor.

Figure 3

The electric field at a point outside the resistor is greater than the electric field at a point inside the resistor.

Figure 4

The electric field at a point outside the resistor is less than the electric field at a point inside the resistor.

Figure 5

A simple circuit with a “resistor” (a thin section of the wire).

Figure 6

The electric field at a point outside the thin section is equal to the electric field at a point inside the thin section.

Figure 7

The electric field at a point outside the thin section is greater than the electric field at a point inside the thin section.

Figure 8

The electric field at a point outside the thin section is less than the electric field at a point inside the thin section.