Question

A silver wire is 0.04 mm it is used to make a resistance of 1ohm if the resistivity of silver is 1.6*10^-8 then calculate the length of the wire needed

Answer 1

Answer:

$l=7.853\ cm\approx0.079\ m$

Explanation:

Given:

• thickness of silver wire, $d=0.04\ mm=4\times 10^{-5}\ m$

• resistivity of silver, $\rho=1.6\times 10^{-8}\ \Omega.m$

• resistance, $R=1\ \Omega$

As we know, resistance:

$R=\rho \frac{l}{a}$

$1=1.6\times 10^{-8}\times \frac{l}{\pi.\frac{d^2}{4} }$

$\frac{1}{1.6} \times 10^8\times \pi\times \frac{(4\times 10^{-5})^2}{4} =l$

$l=7.853\ cm\approx0.079\ m$