I have made an small application of a railgun. It looks simple but I don't get its principle involved here. On a cardboard, two strips of aluminum foils are pasted qith an equal distance apart from each other, resembling a train's path. A pair of alligator clips, both ends have 'head', in which the front heads of each are attached to one of the foils. the other ends on a 9V battery. I assembed a pair of magnets connected by a 3 inch steel cut from a coathanger at the center of each magnet. Then here's the fun. When I placed the "wheel" at the path, it moves away from the start.