Q95 / 160 · JIPMER 2011 · Physics

A current of 5 A is passing through a metallic wire of cross-sectional area $4 \times 10^{-6} \mathrm{~m}^2$. If the density of charge carriers of the wire is $5 \times 10^{26} \mathrm{~m}^{-3}$, then the drift velocity of the electrons will be

  • A
    $1 \times 10^2 \mathrm{~m} / \mathrm{s}$
  • Correct answer
    B
    $1.56 \times 10^{-2} \mathrm{~m} / \mathrm{s}$
  • C
    $1.56 \times 10^{-3} \mathrm{~m} / \mathrm{s}$
  • D
    $1 \times 10^{-2} \mathrm{~m} / \mathrm{s}$

Solution

Drift velocity, $v_d=\frac{1}{n e A}$ $\Rightarrow v_d=\frac{5}{\left(5 \times 10^{26}\right) \times\left(1.6 \times 10^{-19}\right) \times\left(4 \times 10^{-6}\right)}$ $=\frac{1}{64}=1.56 \times 10^{-2} \mathrm{~ms}^{-1}$

Hence, the correct answer is option: 'B'.

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