Q118 / 150 · MHT CET 2020 (20 Oct Shift 1) · Physics

An electron at rest is accelerated by a potential ' $\mathrm{V}_{1}$ ', in uniform magnetic field experiences a force 'F $1^{\prime}$. When potential is changed to ${ }^{\prime} \mathrm{V}_{2}^{\prime}$ ', the force experienced by the electron gets doubled. The ratio of $V_{1}$ to $V_{2}$ is

  • A
    $4: 1$
  • B
    $2: 1$
  • C
    $1: 2$
  • Correct answer
    D
    $1: 4$

Solution

An electron at rest is accelerated by a potential ' $V_{1}$ ', in uniform field experiences a force ' $F_{1}$ '. When potential is changed to ' $V_{2}$ ', the force experienced by the electron gets doubled. The ratio of $V_{1}$ to $V_{2}$ is $1: 2$. $\mathrm{F}_{1}=\frac{\mathrm{eV}_{1}}{\mathrm{~d}} 2 \mathrm{F}_{1}=\frac{\mathrm{eV}_{2}}{\mathrm{~d}}$ $\frac{V_{1}}{V_{2}}=\frac{1}{2}$

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

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