||In this work we analyse the conceptions that the students of different degree of instruction use when they interpret and make predictions on the functioning of the electrical circuits, in various problematic situations. For this reason we have studied the evolution of such ideas, in different educational levels, from high school until the end their university studies. The obtained results have shown the existence of important differences of conceptual type between apprentices and experts and the persistence of numerous alternative conceptions in all the teaching levels, even in individuals who have finished their studies in the university and aspire to be physics teachers. Also we have observed that the students maintain a considerable degree of confidence in their personal conceptions and that this safety increases with the instruction level. On this base we have formulated, finally, some interesting implications for the teaching of the electrical circuits and the initial training of the secondary education teachers.