Conductor Cross Section: Small vs Large Copper Wire in 9V Battery Experiment

[leVanw]

I connected the small copper wire and the light to a 9V battery, the light came on, but when I changed to the large copper wire, the light did not light up.

 

[Baluncore]

Welcome to PF.
The large copper wire might be insulated with a clear layer of lacquer? See if you can remove a clear surface layer by scraping the surface with a sharp blade.
Any luck?