IanM writes:

Please explain *CLEARLY* how increasing the thickness of any uniform
substance can *increase* the resistance if everything else remains
unchanged.


The resistance varies inversely to the cross-section of the conductor.

AWG 12 wire resistance/foot = 1.619Ohms.
AWG 10 wire resistance/foot = 1.018ohms.
AWG 8 0.6405

http://www.interfacebus.com/Copper_Wire_AWG_SIze.html

Ergo, heavier wire, less resistance.

So assume that a 100watt blub rated at 130V filament consumes
0.769231 amperes of current. From ohms law, one can then derive
the resistance of the conductor as (R=V/I) 156 ohms.

Now run that same bulb at 120volts, the current in the filament
(per again ohms law) will be (I=V/R) 0.769231 (i.e. the same current).

However, the power consumed (P=IV) will only be 92.3 watts, thus
reducing the lumen output of the bulb.