The idea of TPACK was developed from the idea of Shulman (1986) who considered that teacher competent should be measured by considering the ability in content and pedagogy knowledge (PCK) Figure 1.
Figure 1: Content and Pedagogical Knowledge (Shulman, 1986)
Shulman, did not discuss technology and its relationship to pedagogy and content. Its Kohler and Mishra (2009) who added technology in the PCK to have TPCK. Thus the interaction in the TPACK model goes beyond PCK to have TPK and TCK. Which they further integrate to form TPACK which is technological, pedagogical and content knoweldge. A teachers is supposed to have the necessary competencies in TK, CK, PK as well as in the combinations of TPK, TCK and CPK . The core component of the TPACK is knowledge of the teacher on each item (content, pedagogy and technology). Thus, TPACK can be described as interplay between knowledge about technology (TK), knowledge about content (CK) and Knowledge about the pedagogy (PK) which further integrates into TPK, TCK and PCK Figure 2.
Figure 2: Interaction between TK, CK and PK (Koehler & Mishra, 2009)
A teacher is expected to develop the capability of negotiating these relationships to have good knowledge of the content which he teaches (say Chemistry), conversant with varieties of pedagogies available for a given topic or content (collaborative, task oriented etc) and has the ability to use various technologies (iPod, computer etc) in relation to the nature of the content or topic he want to teach and the pedagogical approach he has chosen.
Koehler, M. J., & Mishra, P. (2009). What is technological pedagogical content knowledge? Contemporary Issues in Technology and Teacher Education, 9(1), 60-70.
Shulman, L. S. (1986). Those who understand: Knowledge growth in teaching. Educational Researcher, 15(2), 4-14.