2. Questions Bank
  3. JEE Main & Advanced
  4. Physics
  5. Electrostatics & Capacitance

JEE Main & Advanced Physics Electrostatics & Capacitance Question Bank Electric Field and Potential

  • question_answer
    Four identical charges \[+\,50\,\mu C\] each are placed, one at each corner of a square of side \[2\,m\]. How much external energy is required to bring another charge of \[+\,50\,\mu C\] from infinity to the centre of the square            \[\left( \text{Given}\frac{\text{1}}{\text{4}\pi {{\varepsilon }_{\text{0}}}}=9\times {{10}^{9}}\frac{N{{m}^{2}}}{{{C}^{2}}} \right)\]

    A)                    \[64\,J\]

    B)            \[41\,J\]

    C)                    \[16\,J\]

    D)                                      \[10\,J\]

    Correct Answer: A

    Solution :

                         Potential at the centre of square                     \[V=4\,\times \,\left( \frac{9\times {{10}^{9}}\times 50\times {{10}^{-6}}}{2/\sqrt{2}} \right)=90\sqrt{2}\times {{10}^{4}}V\] Work done in bringing a charge (q = 50 mC) from ¥ to centre (O) of the square is \[W=q\,({{V}_{0}}-{{V}_{\infty }})=q{{V}_{0}}\] Þ \[W=50\times {{10}^{-6}}\times 90\sqrt{2}\times {{10}^{4}}=64J\]     


You need to login to perform this action.
You will be redirected in 3 sec spinner