In this study, an adaptive educational system based on AHAM reference was introduced to teach stepper motors being an important topic in the vocational education. In the system, a domain model for stepper motors was designed and a user overlay model was created based on the domain model. Naive Bayes Classifier (NBC), commonly used in adaptive educational hypermedia systems, was preferred in the application for modeling students in vocational education. Students were classified using NBC as "beginner", "intermediate" or "advanced" based on their knowledge level about the domain model. The system gathers data from the users (students) on-line as well as updates the user models continuously. Thus, the system got the on-line adaptability. Moreover, the system has such abilities as guiding and serving additional explanations according to the users' preferences and defects in the knowledge domain.