well, I've been trying to make a level out of an idea I had, and it included a ball destroying the main power source. but when i try it out, the ball goes THROUGH the mps, instead of destroying it, any ideas about why? how to fix it? i can't test my level =\

I think that's intentional. The designers of the game probably figured that the power source shouldn't be a destructible object. You can get around that by putting something in between the power source and what it's powering that can be destroyed. Like maybe you have a lightbulb that powers a solar panel that is right next to it, and all you have to do is destroy the lightbulb or panel. Of course the lighbulb and panel should not be connected by a wire.

yes well, I solved it somehow like that..

suppose a magnet grabs an object, if that object is removed, will it start grabbing another?

That is logical. The power source is also the reset button, so if you destroy the power source you get stuck and can't continue.