A current of $5\, A$ passes through a copper conductor (resistivity $= 1.7\times10^{-8}\,\Omega \,m$) of radius of cross-section $5\, mm$. Find the mobility of the charges if their drift velocity is $1.1\times10^{-3}\, m/s$ ................ $m^2/Vs$
JEE MAIN 2019, Medium
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$ \mu =\frac{V_{d}}{E} \quad 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\, \mathrm{m}^{2} / \mathrm{Vs} $
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