"MG" wrote:

For example if the wall were made of copper, then the voltage between any
two points would be minuscule.


I don't think that is correct, or even close for any points except
those immediately adjacent to the wall.

for points immediately adjacent to the outlet contacts, it is clearly
200 or 220 or whatever it is being fed with.
More important any way would be the current flow, which will depend on
the resistance of all portions of all current paths.
jk