Question

What is the resistance of a copper wire 200 ft long and 0.01 in. in diameter (T 20°C)?

Answer 1

Answer:

R = 20.21 ohms

Explanation:

Given that,

The length of the wire, l = 200 ft

The diameter of the wire, d = 0.01 in

Radius, r = 0.005 in

200 ft = 60.96 m

0.005 in = 0.000127 m

The resistivity of copper is, $\rho=1.68\times 10^{-8}\ \Omega-m$

So, the resistance of a wire is given by :

$R=\rho \dfrac{l}{A}\\\\R=\rho \dfrac{l}{\pi r^2}\\\\R=1.68\times 10^{-8}\times \dfrac{60.96 }{\pi \times (0.000127 )^2}\\\\R=20.21\ \Omega$

So, the resistance of the copper wire is 20.21 ohms.