Question

What length of copper wire 1.6 mm in diameter is needed to make a 18 ohm resistor at 18 degrees C.

Answer 1

i am taking resistivity  of copper in this question ρ = 1.724 x 10^-8

if you have different data , then let me know

  

R = ρ L /A

A = pi*r^2 = pi* ( 1.6*10^-3 /2)^2 =2.0106193e-6 m²

R = ρ L /A

18 = 1.724 x 10^-8 *L /(2.0106193e-6)
from here L≈2099.25 m

so length we need L ≈2099.25 m

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