The self-efficacy beliefs of prospective teachers of secondary education in their physics classes are analysed, observing their perceived ability to successfully teach their students and to relate to the emotions they foresee in their future physics classes. To this end, a questionnaire was designed inquiring into the possible emotions they might feel when teaching physics content. The sample consisted of 178 prospective secondary education teachers of the University of Extremadura in Badajoz (Spain) taking the official paedagogical aptitude course (the "CAP") during the 2008/2009 academic year. Generally, the results showed the prospective teachers to feel qualified to teach physics content with the training they had received in their respective undergraduate degree courses. Positive self-efficacy decreased and negative self-efficacy increased if there existed negative emotions. (Contains 1 table and 4 figures.)