A copper wire of length 10 m and radius $\left(10^{-2} / \sqrt{\pi}\right) \mathrm{m}$ has electrica

Question

A copper wire of length 10 m and radius $\left(10^{-2} / \sqrt{\pi}ight) \mathrm{m}$ has electrical resistance of $10 \Omega$. The current density in the wire for an electric field strength of $10(\mathrm{~V} / \mathrm{m})$ is\

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(d) : length, $l=10 \mathrm{~m}$\ radius, $r=\frac{10^{-2}}{\sqrt{\pi}} m$\ Resistance, $R=10 \Omega$\ Electric field, $E=10 \mathrm{~V} / \mathrm{m}$\ The current density, $j=\sigma E=\frac{E}{ho}$\ So, $ho=\frac{R A}{l}=\frac{10 	imes \pi 	imes \frac{10^{-4}}{\pi}}{10}=10^{-4} \Omega \mathrm{~m}$\ From equation (i),\ $V=\frac{10}{10^{-4}}=10^{5} \mathrm{~A} / \mathrm{m}^{2}$