Think of two torus-shaped tubes. Each tube is filled with electrically-charged ping pong balls. The inside of the tube is smooth and friction-less. So someone gives the ping pong balls inside a push, and the balls start moving in a circle. The same thing happens in the 2nd torus. Due to the movement of the charged balls, there is a current and a magnetic force is experienced by both tori. So now both tori possess some form of magnetic potential energy. It's as though energy was created from nowhere. Can someone help me resolve this?