The specific resistance of a wire is $\rho $, its volume is $3\,{m^3}$ and its resistance is $3\, ohms$, then its length will be
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${\rm{Volume}} = Al = 3 \Rightarrow A = \frac{3}{l}$
${\rm{Now}}$$R = \rho \frac{l}{A} \Rightarrow 3 = \frac{{\rho \times l}}{{3/l}} = \frac{{\rho {l^2}}}{3}$$ \Rightarrow {l^2} = \frac{9}{\rho } = \frac{3}{{\sqrt \rho }}$
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