If my adapter says 1A or 2.1 which port should I use for my iPod nano?
Solution 1:
It doesn't actually matter.
The iPod will require 1A, but as Amps are "pulled" by the deive rather than being "pushed" by the socket, the end result is the same whichever you plug it into.
You will only notice a difference if you plug in an iPad which needs 2A. If it can only pull 1A it will charge more slowly.