The aim of this study was to investigate the impact of the course materials developed in accordance with 7E model in the unit of electromagnetism in high school physics class on students' conceptual success. The present study was conducted with a total of 52 11th grade students in two separate classrooms at a high school. The action research design was used as the research method. The data of the study were collected through worksheets, open-ended and multiple-choice conceptual achievement tests and individual interviews. The worksheets, which were developed in order to ensure conceptual change and development based on experimental activities, were prepared and administrated in accordance with 7E model. In the research, 6 students with high level, moderate level and low level of conceptual changes were interviewed about their achievements. The activities and materials, which were applied according to the average scores of students, were found to be effective on conceptual development and eliminating existing misconceptions of students about the subject of electromagnetism. Recommendations were made in accordance with the findings obtained.