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

  • question_answer
    Two charges of magnitude 5 nC and -2 nC, one placed at points (2 cm, 0, 0) and (xcm, 0, 0) in a region of space, where there is no other external field. If the electrostatic potential energy of the system is\[-0.5\,\,\mu J\]. The value of x is:

    A) 20 cm                          

    B) 80 cm   

    C) 4 cm                            

    D) 16 cm

    Correct Answer: A

    Solution :

    (a) 20 cm Potential energy of system \[U=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{q}_{1}}{{q}_{2}}}{r}\] \[\Rightarrow -0.5\times {{10}^{-6}}=\frac{9\times {{10}^{9}}\times 5\times {{10}^{-9}}\times \left( -2 \right)\times {{10}^{-9}}}{\left( x-2 \right)\times {{10}^{-2}}}\]\[\Rightarrow x=20\,\,cm\]


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