JEE MAIN - Physics (2019 - 10th April Morning Slot - No. 18)
A current of 5 A passes through a copper
conductor (resistivity = 1.7 × 10–8 $$\Omega $$m) of radius
of cross-section 5 mm. Find the mobility of the
charges if their drift velocity is 1.1 × 10–3 m/s.
1.3 m2/Vs
1.0 m2/Vs
1.8 m2/Vs
1.5 m2/Vs
Explanation
$$\mu = {{{V_d}} \over E}\,\,\,\,\,\,E = \rho J$$
$$ = {{1.1 \times {{10}^{ - 3}}} \over {1.7 \times {{10}^{ - 8}} \times {5 \over {\pi \times 25 \times {0^{ - 6}}}}}}$$
$$ = {{1.1 \times {{10}^{ - 3}} \times \pi \times 25 \times {0^{ - 6}}} \over {1.7 \times {{10}^{ - 8}} \times 5}} \approx 1.01\,{m^2}/Vs$$
$$ = {{1.1 \times {{10}^{ - 3}}} \over {1.7 \times {{10}^{ - 8}} \times {5 \over {\pi \times 25 \times {0^{ - 6}}}}}}$$
$$ = {{1.1 \times {{10}^{ - 3}} \times \pi \times 25 \times {0^{ - 6}}} \over {1.7 \times {{10}^{ - 8}} \times 5}} \approx 1.01\,{m^2}/Vs$$
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