• # question_answer A current of 5 A passes through a copper conductor (resistivity$=1.7\times {{10}^{-8}}\Omega m$) of radius of cross-section 5 mm. Find the mobility of the charges if their drift velocity is $=1.1\times {{10}^{-3}}m/s.$ [JEE Main 10-4-2019 Morning] A) $1.3\text{ }{{m}^{2}}/Vs$            B) $1.5\text{ }{{m}^{2}}/Vs$C) $1.8\text{ }{{m}^{2}}/Vs$            D) $1.0\text{ }{{m}^{2}}/Vs$

$\mu =\frac{{{V}_{d}}}{E}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,E=\rho J$             $=\frac{1.1\times {{10}^{-3}}}{1.7\times {{10}^{-8}}\times \frac{5}{\pi \times 25\times {{10}^{-6}}}}$             $=\frac{1.1\times {{10}^{-3}}\times \pi \times 25\times {{10}^{-6}}}{1.7\times {{10}^{-8}}\times 5}\approx 1.01{{m}^{2}}/Vs$