An interactive simulation in which students use a model of charged objects to explain how charges interact and construct an understanding of Coulomb's Law. It is concerned with comparing ions and neutral atoms. The model allows the user to investigate the relationships between sign of charge, magnitude of charge, and distance between ions. The model illustrates the operation of three types of electroscopes. Next it visually explores how a static charge can bend the path of a moving electron, and then graphically and numerically explores Coulomb's Law. Lastly a model that illustrates polarization of charge illustrates why a charged balloon is attracted to a neutral wall. The system allows students to enter their multiple choice and written answers throughout the activity and generate a report of their responses at the end even if they are not logged into the system.