"compression" of an electrostatic charged sphere Everytime i propose a new motion machine from my ignorance or misunderstunding of physics, your explanations solve some questions, but open new others: I proposed a system that acumulated electrons on a sphere surrounded by an electrons charged outter sphere, then connecting them, all the electrons will pass to the outter sphere. Now I know that the outter sphere will create a voltage into the cavity that will not let the electrons go into the inner sphere, unless you force them aplying energy. (Urkil knows how hard it was to explain me that). OK, so the electrons on the outter sphere will create a constant voltage inside. Now, from my last post, a new question cames to my head: If the voltage inside the cavity is constant, we have to expend no energy to move a free electron that were inside this cavity. Then, imagine you can "shrink" the sphere. As the inside voltage the electrons generate is constant, it will cost you nothing to move the electrons, but once you've reduced the sphere, the voltage is more negative. How this proccess happens? Will the electrons know that the voltage will decrease before it really decreases?. (Think about the graphic of potential respect the distance to the centre of the sphere, and you'll see that reducing the radius, the potential will decrease, but it stays always horizontal, so "in principle" it will cost you nothing to "shrink" the sphere).