Qualitative investigation into students’ use of divergence and curl in electromagnetism

Many students struggle with the use of mathematics in physics courses. Although typically well trained in rote mathematical calculation, they often lack the ability to apply their acquired skills to physical contexts. Such student difficulties are particularly apparent in undergraduate electrodynamics, which relies heavily on the use of vector calculus. To gain insight into student reasoning when solving problems involving divergence and curl, we conducted eight semistructured individual student interviews. During these interviews, students discussed the divergence and curl of electromagnetic fields using graphical representations, mathematical calculations, and the differential form of Maxwell’s equations. We observed that while many students attempt to clarify the problem by making a sketch of the electromagnetic field, they struggle to interpret graphical representations of vector fields in terms of divergence and curl. In addition, some students confuse the characteristics of field line diagrams and field vector plots. By interpreting our results within the conceptual blending framework, we show how a lack of conceptual understanding of the vector operators and difficulties with graphical representations can account for an improper understanding of Maxwell’s equations in differential form. Consequently, specific learning materials based on a multiple representation approach are required to clarify Maxwell’s equations.

Figure 1

Example of a blending diagram from the analysis by Hu and Rebello [18].

Figure 2

Field vector plots that were shown to students during the interview: (a) the electric field corresponding to the charged cylinder of question 2(a); (b) a field used to explain to students how they can decide whether the divergence is zero or not at a certain location.

Figure 3

Student sketch of the electric field of a charged cylinder [question 2(a)].

Figure 4

Examples of student drawings of electric fields.

Figure 5

Examples of blends concerning the understanding of the divergence of an electric field.