JEE Main & Advanced Physics Electrostatics & Capacitance Question Bank Mock Test - Electrostatics

  • question_answer
    An electric dipole is situated in an electric field of uniform intensity \[E\] whose dipole moment is p and moment of inertia is I. If the dipole is displaced slightly from the equilibrium position, then the angular frequency of its oscillations is

    A) \[{{\left( \frac{pE}{l} \right)}^{1/2}}\]   

    B) \[{{\left( \frac{pE}{l} \right)}^{3/2}}\]

    C) \[{{\left( \frac{l}{pE} \right)}^{1/2}}\]               

    D) \[{{\left( \frac{p}{lE} \right)}^{1/2}}\]

    Correct Answer: A

    Solution :

    [a] When dipole is given a small angular displacement \[\theta \]about its equilibrium position, the restoring torque will be \[\tau =-pE\sin \theta =-pE\theta (assin\theta =\theta )\] or \[I\frac{{{d}^{2}}\theta }{d{{t}^{2}}}=-pE\theta (as\,\tau =I\alpha =I\frac{{{d}^{2}}\theta }{d{{t}^{2}}})\] or \[\frac{{{d}^{2}}\theta }{d{{t}^{2}}}=-{{\omega }^{2}}\theta \,\,\text{with}\,\,{{\omega }^{2}}=\frac{pE}{I}\Rightarrow \omega =\sqrt{\frac{pE}{I}}\]  


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