Q105 / 180 · JIPMER 2018 · Physics

A current $i$ is flowing through the wire of diameter (d) having drift velocity of electrons $\mathrm{v}_{\mathrm{d}}$ in it. What will be new drift velocity when diameter of wire is made $\mathrm{d} / 4$ ?

  • A
    $4 v_d$
  • B
    $\frac{v_d}{4}$
  • Correct answer
    C
    $16 v_d$
  • D
    $\frac{v_d}{16}$

Solution

$\because$ Current, $\mathrm{I}=\mathrm{nAev}_{\mathrm{d}}$ or $\quad \mathrm{v}_{\mathrm{d}} \propto \frac{1}{\mathrm{~A}}$ If diameter of wire is $\frac{\mathrm{d}}{4}$, then area will be $\frac{\mathrm{A}}{16}$, so new drift velocity $=16 v_d$.

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

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