$(a)$ Resistivity of iron is $10 \times 10^{-8} \;\Omega m$ and of mercury is $94 \times 10^{-8}\; \Omega m$. Which among iron and mercury is a better conductor ? Give reason.

$(b)$ Resistivity of a material $A$ is in the range of $10^{10}-10^{\text {14 }} \;\Omega m$ while that of $B$ is in the range of $10^{-6}-10^{-8} \;\Omega$ m. Which of the two will behave as an insulator and why?

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$(a)$ Iron, because lower the resistivity, better is the conductor.

$(b)$ Material $A$, because insulators have higher resistivity.

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