The voltage varies depending on resistance.
I never contradicted that.
Another example is that same battery and a 30ft wire. the voltage measured at the end of that 30ft wire will not be 12v because of the resistance of the wire. if the resistance of the wire is known, what formula will tell me the resultant voltage?
Here's a site for calculating voltage loss in a wire...
http://genuinedealz.com/voltage-drop.html
You'll notice there is an input for Enter Load in amps. Guess what's missing from your description.