12th Class Physics Electric Charges and Fields Question Bank Case Based (MCQs) - Electric Charges and Fields

  • question_answer
    An electric dipole consists of two opposite charges, each of magnitude \[1.0\,\mu C\] separated by a distance of 2.0 cm. The dipole is placed in an external field of \[{{10}^{5}}\,N\,{{C}^{-1}}\]. The maximum torque on the dipole is

    A) \[0\centerdot 2\times {{10}^{-3}}Nm\]

    B) \[1\times {{10}^{-3}}\,Nm\]

    C) \[2\times \,{{10}^{-3}}\,Nm\]

    D) \[4\times {{10}^{-3}}\,Nm\]

    Correct Answer: C

    Solution :

    The maximum torque on the dipole in an external electric field is given by \[\tau =pE=q\left( 2a \right)\times E\] Here, \[q=1\,\,\mu C={{10}^{-6}}\,C\], \[2a=2\,cm\,=2\times {{10}^{-2}}m\] \[E={{10}^{5}}\,N{{C}^{-1}},\,\tau =?\] \[\therefore \,\,\,\,\,\,\tau ={{10}^{-6}}\times 2\times {{10}^{-2}}\times {{10}^{5}}\] \[=2\times {{10}^{-3}}\,N\,m\]


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