We have developed, implemented, and assessed a teaching-learning sequence that aims to enhance students' understanding of the divergence and curl of electromagnetic fields. We designed guided-inquiry worksheets based on student difficulties we identified during semiquantitative and qualitative studies and discussions in the literature. A multiple representation approach was adopted to strengthen the link between graphical representations of vector fields, calculations involving divergence and curl, and Maxwell's equations in differential form. We used the Design, Functions, Tasks framework to optimize learning with the multiple external representations exhibited in our learning materials. These guided-inquiry worksheets used in small-group tutorials comprise short open-ended questions that encourage discussions in small groups of students. They were implemented in three consecutive years in a second-year electrodynamics course at KU Leuven. The intervention was assessed using the same pretest and post-test design adopted to evaluate learning in the original instruction. In addition, we gauged our students' opinions on the intervention. We observed that our intervention positively affected our students' structural understanding of the vector operators, their ability to interpret divergence and curl in graphical representations of vector fields, and their conceptual understanding of Maxwell's equations in differential form. In addition, our students indicated that they enjoyed the teaching approach, felt they learned something from the worksheets, agreed with the difficulty level of the materials, and would like similar tutorials on different subjects.