In this demo, we present Spark, an augmented circuit exhibit that enables visitors to make circuits using a set of tangible components and observe a simulation of electrons flowing through the circuit. Our goal is to use multiple representations of a circuit to help convey basic concepts of current and resistance. In Spark, the electron simulation and tangible circuit components are coupled using augmented reality techniques. We developed our system through a three-year iterative design process. We tested earlier versions of the design at a science museum with parent-child dyads and found that having access to the electron simulation could benefit children to better understand the concepts of electricity. We also observed that coupling the electron simulation through augmented reality can significantly enhance the learning benefits of the exhibit.