Question

What length of copper wire of specific resistance 1.7×10^-8 ohm/m and radius 1 mm is required so that its resistance is 1 ohm ?

Answer 1

As
resistance(R)= specific resistance(α)*length(l)/ Area(A)
therefore, l = R*A/α
i.e. l = 1*3.14*10^-6/1.7*10^-8
l ~ 184 metre

Answer 2

Explanation:

the answer is explained in the picture