PhET simulations: Should we show the invisible?

During hundreds of student interviews, we have seen students engage in productive science-like exploration with PhET Interactive Simulations (sims). Recently we have been working to determine what specific features of PhET sims are necessary to make them effective learning tools. In this study, we compare differences in student learning and sim investigation when the sim either shows or hides representations of abstract or invisible phenomena such as a magnetic field or electron flow in a wire. Specifically, we conducted individual interviews with introductory-level university physics students, some of whom were using Faraday’s Electromagnetic Lab as designed and others who used a version of the same sim but without the invisible representations. Preliminary results indicate that students who saw the representation of electron flow and the magnetic field are more ready to learn about flux compared to students who did not see these representations.