The aim of this study was to detect primary students' conceptions about the origin and conveyance of electric current and about the connection of household electric appliances. In total, 383 students (aged 11-12) from the town of Volos, Greece, participated; 213 of them drawn from experimental classes and 170 from control groups. The results reported are derived from the analysis of answers to four questions included in a written questionnaire (pre-test and post-test). Before teaching, children tended to suggest that three appliances can work together at the same time because the electric current is powerful and exists everywhere. They drew one cable for the electricity's transmission from its origin to 'our house' and they represented each electrical device working independently with its own wire connected to a wall-socket. After a 9-hour constructivist teaching intervention, many of the students in the experimental classes accepted that we can bring three electric devices into operation at the same time, and they understand that they can be connected in parallel each one having its own circuit. Also, a lot of children drew two cables (i.e. a circuit) from the electricity company up to 'our house' and represented the parallel connection of three electrical appliances. The answers/drawings of the traditional classes had not developed after teaching.