This paper reports upon an active learning approach that promotes conceptual change when studying direct current electricity circuits, using free open source software, "Qucs". The study involved a total of 102 prospective mathematics teacher students. Prior to instruction, students' understanding of direct current electricity was determined by a subset of a previously developed multiple choice conceptual test. All students received an active learning instruction using "Qucs" simulations. After instruction, the same test was administered to the students to determine the effectiveness of the instruction they received. Paired t-test analyses showed that students' progress on understanding of direct current electricity was significant. A six week delayed post-test revealed that this observed improvement promised to be durable, at least in the short term. Students' evaluation of using "Qucs" is also reported. (Contains 5 tables and 4 figures.)