The resistance of the piece of wire is

where

is the resistivity of the copper

is the length of the piece of wire

is the cross sectional area of the wire
By substituting these values, we find the value of R:

Then, by using Ohm's law, we find the potential difference between the two points of the wire:
Answer:
even if it all could be used, it wouldn't be enough
Explanation:
The land area of the US is about 5.45% of the world's area, so the amount of released heat over the area of the US is on the order of 2.4 Tw. Current technology for converting geothermal energy to electricity is about 12% efficient, so the available energy might amount to 0.29 Tw if it could all be captured.
Energy consumption in the US in 2019 was on the order of 0.46 Tw. This suggests that even if <em>all</em> of the thermal energy radiated by the Earth from the US could be turned to useful forms of energy, it would meet only about 60% of the US need for energy.
During convection of air currents, cool air sinks. <em>(b)</em>
I think it is the core and outer core.
hope this helped.