Yes, you can reclaim used electrical wire with solid copper conductors. You would need to strip and anneal it first. Annealing is a process of heat treatment that makes the wire soft enough to bend.
There are a few articles in
bonsaiTALK Links under Techniques->Wiring or you can search there on ANNEAL
Of course
TreeBay Bonsai Tools & Supplies carries professionally annealed copper wire, and aluminum wire, in a variety of sizes. Look in the Supplies folder
Regards,
Matt