1. The problem statement, all variables and given/known data Find the resistance of a 1.4 m length of copper wire with diameter of 5*10^-3 m. 2. Relevant equations R = p(L/A) where p = resistivity of copper, L = length, A = area 3. The attempt at a solution The resistivity of copper is (1.69 * 10^-8). Radius is d/2 (5*10^-3) / (2) = (2.5*10^-3) With the radius, the Area A = pi(2.5*10^-3)^2 = (1.96*10^-5). Plugging it into the equation R = p(L/A) (1.69*10^-8)*(1.4) / (1.96*10^-5) = (1.2*10^-3) Ohm There were two similar questions like this where the same approach yield me the correct answer. Somehow this answer I get is incorrect. What am I doing wrong? On a side note, how many questions may I post?