Question

The resistance of a wire fo length 300 m and cross section area $1.0m{m}^2$ made of material of resistivity $1.0\times {10}^{-7}\Omega m$ is
(a) $2\Omega$ (b) $3\Omega$ (c) $20\Omega$ (d) $30\Omega$

Answer 1

Length 300 m and cross section area $1.0m{m}^2$ made of material of resistivity $1.0\times {10}^{-}7$ Ωm
$R=p\frac{L}{A}$

$R=1.0\times {10}^{-}7\times \frac{300}{(1\times {10}^{-}3{)}^2}$

=30 Ω