Thunderstorm Beginner 08/26/2013 Schematic View of Van de Graaff Generator Intermediate 06/28/2012 Transient Luminous Events Advanced 06/25/2012 Van de Graaff generator Beginner 06/18/2012 Chest x-ray with ECG leads Advanced Raytheon Electrocardiogram Advanced electrocardiogram machine (1911) Advanced