This study aimed to understand the process of transformation in the knowledge structures of learners in the technical upper secondary school course "electric circuit". We examined and compared the pre- and post-unit concept maps of the top and bottom performers in the unit. The influence of "a discipline-based epistemological approach of industrial department electricity" on the transformation of learners' knowledge structures was analyzed through correspondence analysis using interview data. A key characteristic of the knowledge structure transformation in many top-performing students was the labeling of the items considered to prevent fires and accidents when using electrical products. Conceptual knowledge, such as the relationship and regularity of each label, was expressed through first-level labels and structured by relating them to second-level labels. Additionally, both conceptual knowledge of technology and the structuring of conceptual knowledge of science were represented in the concept maps. Regarding the influence of a discipline-based epistemological approach on the structuring of conceptual knowledge in each subject , the results of the correspondence analysis suggest that the transformation of the knowledge structure in "Electric Circuits" was facilitated by the implementation of a Discipline-based Epistemological Approach in each subject within STEAM education.