Most researchers are interested in investigating the impact of a blended learning approach (BLA) on students’ performance, yet this approach’s instructional efficiency has not yet been quantified. Therefore, this research aims to determine the impact of teacher-created online Moodle-based materials in combination with face-to-face learning on student achievement and mental effort, that is, to determine the instructional efficiency of applied teaching approaches at physics classes in high school. For this research, we chose to teach students physical principles of direct current, which involves abstract concepts. Using BLA, students can prepare better for a real experiments in the lab, and this approach also creates a safe environment for students while allowing them to demonstrate the learned physical phenomena. The Moodle platform course is developed for this purpose and implemented in a BLA environment. Students are gradually guided from easier to more difficult concepts in this research, considering the working memory’s capacity and the teaching material requirements. Our results show that the students who used BLA achieved higher scores on the knowledge test, and they also used less mental effort than students that used a conventional teaching approach. We also show that instructional efficiency for BLA is positive and significantly higher than the instructional efficiency of the conventional approach. This research’s results are primarily designed for physics teachers to better understand the effects of the BLA and apply teaching approaches that respect the principles of children’s cognitive development.