Q82 / 160 · JIPMER 2014 · Physics

A charged particle is accelerated by a potential of 200 V . If its velocity is $8.4 \times 10^8 \mathrm{~m} / \mathrm{s}$, then value of $e / m$ for that particle is

  • A
    $17.6 \times 10^{16}$
  • B
    $14.5 \times 10^{12}$
  • Correct answer
    C
    $1.76 \times 10^{15}$
  • D
    $1.45 \times 10^{15}$

Solution

If electron is accelerated by voltage $V$, then its kinetic energy $=\frac{1}{2} m v^2=q V$ $\begin{aligned} \frac{q}{m} & =\frac{v^2}{2 V} \\ & =\frac{\left(8.4 \times 10^8\right)^2}{2 \times 200}=1.76 \times 10^{15}\end{aligned}$

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

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