The objective of this study was to characterise the changes in the Pedagogical Content Knowledge (PCK) about electric fields of two Colombian physics teachers (Isabel and Alejandro) at the high school level (pupils of ages 17-19), the emotions and their relationship with PCK. The research was conducted during two consecutive years, before and after their participation in a project of innovation on teaching electric fields. The method proposed corresponds to the descriptive type of case study. The PCK-related categories were grouped into two basic tendencies--traditional teacher-centred (TT) and pupil-centred or innovative tendency (TC)--plus an intermediate tendency (TI). The results indicated that, for Isabel, the PCK components that show the greatest progression over time are curricular knowledge and teaching strategies, evolving from a teacher-centred PCK to another which does not have a defined tendency. Alejandro, whose starting point was a PCK corresponding to an intermediate tendency in curricular knowledge, was less willing to change, especially with regard to his knowledge about teaching strategies. Finally, the causes of both the positive and the negative emotions are mostly related to the curricular knowledge and the content being taught.