You'll want to attach something to the other end that will enter the solution
without submerging the copper wire (the copper will dissolve over time).
A stainless steel spoon is what I use. Never, NEVER, let the two
electrodes, or the submerged objects, touch while the current is on. Your
adapter will short, and possible cause a fire.
In this photo, you can see that I've got the spoon
and dime in the solution. You want to submerge the dime, but not totally
submerge the alligator clip. Also, you'll notice that I don't let the
metal objects touch.