Regarding how resistance varies with diameter I've read this simple explanation on Quora:
As electrons move across a wire, they constantly collide with atoms making up a wire. These collisions impede the flow of electrons and are what cause the wire to have resistance.Thus, if the diameter of the wire were larger, it would only make sense that the electrons don't collide as much, therefore creating less resistance due to a larger wire.
But doesn't a larger wire mean more atoms (I assume the number of atoms increases proportionally with the diameter of the wire?) meaning same amount of collisions ie. same resistance?
I don't question the fact that resistance decreases with diameter, but this explanation doesn't make sense to me.