A CD with one side covered in foil can be made to spin at high speed by using static electricity, or high voltage DC. With the CD on a spindle with the foil side up, areas under the CD can be charged by nearby electrodes. If the electrodes are placed either side of the CD and just underneath it, charge will be deposited on the plastic surface of the disk.
The plastic disc is non conductive, so in order for the charge to get to the other electrode (of opposite polarity), the disk its self must turn. This physical transportation of charge still constitutes a current flow, even though the current does not flow within the material itself. The flowing current is directly proportional to the speed of the rotating disc.
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