Medium MCQ +4 / -1 PYQ · JEE Mains 2025

An electric dipole of mass $m$, charge $q$, and length $l$ is placed in a uniform electric field $\vec{E} = E_0\hat{i}$. When the dipole is rotated slightly from its equilibrium position and released, the time period of its oscillations will be :

  1. A <p>$ \frac{1}{2\pi} \sqrt{\frac{ml}{2qE_0}} $</p>
  2. B <p>$ 2\pi \sqrt{\frac{ml}{2qE_0}} $</p> Correct answer
  3. C <p>$ 2\pi \sqrt{\frac{ml}{qE_0}} $</p>
  4. D <p>$\frac{1}{2 \pi} \sqrt{\frac{2 \mathrm{~m} l}{\mathrm{q} \mathrm{E}_0}}$</p>

Solution

<p>$$\begin{aligned} & \mathrm{I} \omega 2 \theta=\mathrm{q} \ell \mathrm{E}_0 \theta \\ & 2 \mathrm{~m}\left(\frac{\ell}{2}\right)^2 \omega^2=\mathrm{q} \ell \mathrm{E}_0 \\ & \omega^2=\frac{2 \mathrm{qE}_0}{\mathrm{~m} \ell} \\ & \mathrm{~T}=2 \pi \sqrt{\frac{\mathrm{~m} \ell}{2 \mathrm{qE}_0}} \end{aligned}$$</p>

About this question

Subject: Physics · Chapter: Electrostatics · Topic: Electric Field and Field Lines

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