A 1.0-mm Diameter Copper Wire (resistivity 1.68 × 10-8 Ohm ·m) Carries A Current Of 15 A. What Is The Potential Difference Between Two Points 100 M Apart?

32.085 Volts
1mm dia wire  = .5^2 x Pi = 0.7854 mm^2 CSA (Cross sectional Area)
Rho x (l/a) =  1.68^10x-8 x (100mtr / 0.7854^10x-6 mtrs) = 2.139 Ohms
2.139 Ohms x 15 Amps = 32.085 Volt