One of the main components of teachers' pedagogical content knowledge refers to their use of representation forms. In a similar vein, organizing concepts logically and meaningfully is an essential element of teachers' subject matter knowledge. Since subject matter and pedagogical content knowledge of teachers are tightly connected as categories forming their knowledge base, it is reasonable to expect that representation forms and organization of knowledge are related. In order to find out how far these two facets depend on each other, two Finnish upper secondary physics teachers' answers to an electronic questionnaire were analysed as case studies. Questions varied from teachers' organization of knowledge to their representation forms regarding the topics of "magnetic flux density" and "Ampère's law." A concept map constructed by one teacher, led us to an improved description of teachers' knowledge organization. In addition, observed and analysed lessons given by the second teacher shed light on representation forms. Organization of knowledge of the studied topics was investigated by means of recognizing the core concepts, and then interrelations between the other concepts. So, the study could advise physics teacher to more systematically plan and organize their teaching of the studied topics. Other findings illuminate useful representation forms that physics teachers apply during their teaching such as suiting experiments, explanations, and models. Thus, our conceptualization emphasize for teachers to reflect on effective ways to organize their knowledge and, consequently, to select adequate representation forms.