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JEE Main & Advanced Physics Electrostatics & Capacitance Question Bank Self Evaluation Test - Electric Chages and Fields

  • question_answer
    An electric dipole is placed at an angle of \[30{}^\circ \]with an electric field of intensity \[2\times {{10}^{5}}N{{C}^{-1}}\], it experiences a torque of 4 Nm. Calculate the charge on the dipole if the dipole length is 2 cm.

    A) \[8mC~~~~\] 

    B) \[\,4mC\]

    C) \[8\mu C\]

    D) \[\,2mC\]

    Correct Answer: D

    Solution :

    [d] Torque, \[\vec{\tau }=\vec{p}\times \vec{E}=pE\sin \theta \] \[4=p\times 2\times {{10}^{5}}\times \sin 30{}^\circ \] \[\text{or, }p=\frac{4}{2\times {{10}^{5}}\times \sin 30{}^\circ }=4\times {{10}^{-5}}Cm\] Dipole moment, \[p=q\times l\] \[q=\frac{p}{l}=\frac{4\times {{10}^{-5}}}{0.02}=2\times {{10}^{-3}}C=2mC\]


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