Induction to change output voltage of DC.

[Geobio]

I am trying to adjust the output voltage of my 12v DC adapter. Is it possible to wrap the wires of the adapter around a toroid in a closed circuit, and then wrap another wire around the toroid to have the output voltage of this wire decreased, and the current increased?

Example:
http://img27.imageshack.us/img27/7663/showlcb.jpg

 

[berkeman]

I am trying to adjust the output voltage of my 12v DC adapter. Is it possible to wrap the wires of the adapter around a toroid in a closed circuit, and then wrap another wire around the toroid to have the output voltage of this wire decreased, and the current increased?

Example:
http://img27.imageshack.us/img27/7663/showlcb.jpg

From your sketch, you are trying to make a transformer after the 12V adapter. That would only work if the adapter had an AC output. You cannot do that with a DC output.