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QJEEM19Ph222c: JEE Main 2019 Physics - Class 11 JEEM19Ph222c Solution: An electric dipole is formed by two equal and opposite charges…

An electric dipole is formed by two equal and opposite charges q with separation d. The charges have same mass m. It is kept in a uniform electric field E. If it is slightly rotated from its equilibrium orientation, then its angular frequency ω\omega is :-

Multiple Choice Options

  • A qEmd\sqrt {{{qE} \over {md}}}
  • B qE2md\sqrt {{{qE} \over {2md}}}
  • C qE−2md\sqrt {{{qE} \over {-2md}}}
  • D 2qEmd\sqrt {{{2qE} \over {md}}}

Step-by-Step Verified Solution

JEE Main 2019 (Online) 8th April Evening Slot Physics - Rotational Motion Question 160 English Explanation Moment of inertia
(I)=m(d2)2×2=md22(I) = m{\left( {{d \over 2}} \right)^2} \times 2 = {{m{d^2}} \over 2}

Now by τ=lα\tau = l\alpha

(qE)(d sin⁡θ)=md22.α(qE)(d\,\sin \theta ) = {{m{d^2}} \over 2}.\alpha

α=(2qEmd)sin⁡θ\alpha = \left( {{{2qE} \over {md}}} \right)\sin \theta for small θ\theta

⇒α=(2qEmd)θ\Rightarrow \alpha = \left( {{{2qE} \over {md}}} \right)\theta

⇒\Rightarrow Angular frequency ω=2qEmd\omega = \sqrt {{{2qE} \over {md}}}

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