Explanation:
First of all, let's find the cross-sectional area of the copper wire. The radius of the wire half the diameter:
So the area is
Now we can calculate the resistance of the piece of copper wire between the bird's feet, with the formula:
where
is the resistivity of copper
is the length of the piece of wire
is the cross-sectional area
Substituting, we find
And since we know the current in the wire, I=149 A, we can now find the potential difference across the body of the bird, by using Ohm's law: