The resistance of a rectangular block of copper of dimensions $2 \,mm \times 2 \,mm \times 5 \,m$ between two square faces is $0.02 \,\Omega$. What is the resistivity of copper?
A$1.6 \times 10^{-8}\; \Omega$
B$1.6 \times 10^{-6} \;\Omega- m$
C$1.6 \times 10^{-8} \;\Omega-m$
D$0\;\Omega-m$
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C$1.6 \times 10^{-8} \;\Omega-m$
c (c)
$R=\frac{\rho l}{A}$
$0.02=\frac{\rho(5)}{4 \times 10^{-6}}$
$\rho=\frac{8 \times 10^{-8}}{5}$
$\rho=1.6 \times 10^{-8} \,\Omega- m$
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