I'm working on personal research problem while taking leave from school to work a Co-op. The basic idea of what i'm trying to create is a device that will produce electrical charge without having to be charged or have some outside dependence of electric force. the only way I could think to do this -and work with the design limitations i have- is to use a magnet, some copper wire, and a plastic tube. I'm trying to produce a small device that puts out about 40 mV rms. I know that -basically- according to Faraday's Law if you have a changing magnetic flux passing across a wire you will get a current to flow through the wire and a potential will form at the terminals. The way i'm implementing this design is to wrap the wire around the plastic tube -thickness about 2.75mm- and then put a spherical magnet -3mm- on the inside of the tube (I don't have a gauss meter to tell me how strong the magnet is). The magnet will move inside the tube and across the coil of wire and induce a voltage. What i need to know is: with the thickness of this tube; how many turns would I need to create the desired 40 mV; i know the answer lies with Faraday's law but i'm having trouble deriving equations to fit my application. Can someone possibly give some direction? Thank you, -Tyler.