Q141 / 160 · TS EAMCET 2015 · Physics

At a certain place, a magnet makes 30 oscillations per minute. At another place where the magnetic field is doubled, its time period will be

  • Correct answer
    A
    $\sqrt{2} \mathrm{~s}$
  • B
    $2 \mathrm{~s}$
  • C
    $4 \mathrm{~s}$
  • D
    $1 / 2 \mathrm{~s}$

Solution

Time period of magnet in magnetic field $$ T \propto \frac{1}{\sqrt{B}} $$ If magnetic field is doubled, then $$ \begin{aligned} & T^{\prime} \propto \frac{1}{\sqrt{2 B}} \\ & \Rightarrow \quad T^{\prime} \propto \frac{T}{\sqrt{2}}=\frac{2}{\sqrt{2}}=\sqrt{2} \mathrm{~s} \\ & \end{aligned} $$ $$ \text { [oscillation per second }=\frac{30}{60} \text { ] } $$

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

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