Calculate the area of cross-section of a wire if its length is 1.0m, its resistance is $23 Ω$ and the resistivity of the material of the wire is $1.84\times10 Ω\ \text{m}.$
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I = 1.0m
R = 23 ohm
$\rho=1.84\times10^{-6}\ \text{ohm-meter}$
We have
$\text{R}=\rho\frac{\text{I}}{\text{A}}$
$23=1.84\times10^{-6}\times\frac{1}{\text{A}}$
$\text{A}=\frac{1.84\times10^{-6}}{23}$
$=0.08\times10^{-6}\text{m}^2$
$=8\times10^{-8}\text{m}^2$
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