Question

The resistance of copper wire 200 m ling is 21ohm.if its thickness(diameter) is 0.44mm,its specific resistance is around

Answer 1

Explanation:

so first let's find out area of copper wire

d = 0.44 mm = 0.44 / 1000 = 0.00044 (1 m = 1000 mm )

= 44 × 10 ^ -5

area of circle = π r ^2

π ( d/2 ) ^ 2 (r = d/2)

= π [(44×10^-5)/2]^2

= π ( 44×44×10^-10)/ 4

Now ,

resistance = rho × L/ A

= 1.7 × 10^-8 × 2× 10 ^2/ 44×44×10^-10

= 3.4 × 10^-6 / 44×44×10^-10

= 3.4 / 44 × 44 × 10 ^ 4

= 34/ 44 × 44 × 10 ^5

= 34 / 1936 × 10 ^ 5

= 17 / 968

= 0.02 × 10^ -5 approximately