If my adapter says 1A or 2.1 which port should I use for my iPod nano?
It doesn't actually matter.
The iPod will require 1A, but as Amps are &quot;pulled&quot; by the deive rather than being &quot;pushed&quot; 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.