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12th Class Physics Electrostatics & Capacitance Question Bank MCQ - Electrostatic Potential and Capacitance

  • question_answer
    A dipole is placed parallel to the electric field. If W is the work done in rotating the dipole by\[60{}^\circ \], then the work done in rotating it by \[180{}^\circ \]is:

    A) 2W                              

    B) 3W

    C) 4W                              

    D) \[\frac{W}{2}\]

    Correct Answer: C

    Solution :

    (c) 4W Work done in rotating dipole by \[\theta \], \[W=pE\left( 1-\cos \theta  \right)\] \[=pE\left( 1-\cos \,60{}^\circ  \right)=pE\left( 1-\frac{1}{2} \right)=\frac{1}{2}pE\] \[\Rightarrow pE=2W\] \[W'=pE\left( 1-\cos \,180{}^\circ  \right)\] \[W'=2W\left[ 1-\left( -1 \right) \right]\] \[W'=4W\]


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