JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Evening)

  • question_answer
    An electric field of 1000 V/m is applied to an electric dipole at angle of \[45{}^\circ \]. The value of electric dipole moment is \[{{10}^{-29}}Cm.\]What is the potential energy of the electric dipole? [JEE  Main Online Paper (Held on 11-jan-2019 Evening)]

    A) \[-10\times {{10}^{-29}}J\]                              

    B) \[-7\times {{10}^{-27}}J\]

    C) \[-20\times {{10}^{-18}}J\]                  

    D)   \[-9\times {{10}^{-20}}J\]

    Correct Answer: B

    Solution :

    \[E=1000V/m,p={{10}^{-29}}cm,\theta ={{45}^{o}}\] Potential energy stored in the dipole, \[U=-\vec{p}.\vec{E}=-pE\cos \theta \] \[=-{{10}^{-29}}\times 1000\times \cos {{45}^{o}}=-\frac{1}{\sqrt{2}}\times {{10}^{-26}}\] \[=-0.707\times {{10}^{-26}}J\approx -7\times {{10}^{-27}}J\]


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