A cyllindrical copper cable carries a

Question

current of 1200 A. There is a potential difference of 1.6×10−2 V between two points on the cable
that are 0.24 m apart. What is the radius of the cable?

Answer 1

Look up the resistivity of copper. I will call the property r. The units should be ohm-meters.

Then use the formula
R = r*L/A
to solve for A, the area of the circular cross section

In this case, Ohm's law tells you that
R = V/I = 1.6*10^-2/1200 = 1.33*10^-5 ohms

For the radius R, use A = pi R^2