Q103 / 125 · BITSAT 2020 · Physics

Two wires $\mathrm{A}$ and $\mathrm{B}$ of the same material, having radii in the ratio 1: 2 and carry currents in the ratio 4: 1 . The ratio of drift speed of electrons in $\mathrm{A}$ and $\mathrm{B}$ is

  • Correct answer
    A
    16: 1
  • B
    1: 16
  • C
    1: 4
  • D
    4: 1

Solution

Current flowing through the conductor, $\mathrm{I}=\mathrm{n} \mathrm{e} \mathrm{v} \mathrm{A}$. Hence $\frac{4}{1}=\frac{\text { nev }_{\mathrm{d}_{1}} \pi(1)^{2}}{\operatorname{nev}_{\mathrm{d}_{2}} \pi(2)^{2}}$ or $\frac{v_{\mathrm{d}_{1}}}{\mathrm{v}_{\mathrm{d}_{2}}}=\frac{4 \times 1}{1}=\frac{16}{1}$

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

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