NEET Physics Electrostatics & Capacitance Question Bank NEET PYQ - Electrostatics and Capacitance

  • question_answer
    The electric potential at a point in free space due to a charge Q coulomb is \[Q\times {{10}^{11}}V\]. The electric field at that point is  [AIPMPT (S) 2008]

    A) \[4\pi {{\varepsilon }_{0}}Q\times {{10}^{22}}V/m\]

    B) \[12\pi {{\varepsilon }_{0}}Q\times {{10}^{20}}V/m\]

    C) \[4\pi {{\varepsilon }_{0}}Q\times {{10}^{20}}V/m\]

    D) \[12\pi {{\varepsilon }_{0}}Q\times {{10}^{22}}V/m\]

    Correct Answer: A

    Solution :

    [a] Key Idea: Search for the relations of electric potential and electric field at a particular point.
    At any point, electric potential due to charge Q is    \[V=\frac{1}{4\pi {{\varepsilon }_{0}}}.\frac{Q}{r}\]                ...(i)
    where r is the distance of observation point from the charge.
    At the same point, electric field is
    \[E=\frac{1}{4\pi {{\varepsilon }_{0}}}.\frac{Q}{{{r}^{2}}}\]               …(ii)
    Combining Eqs. (i) and (ii), we have
    \[E=\frac{4\pi {{\varepsilon }_{0}}{{V}^{2}}}{Q}=\frac{4\pi {{\varepsilon }_{0}}\times {{(Q\times {{10}^{11}})}^{2}}}{Q}\]
    \[=4\pi {{\varepsilon }_{0}}Q\times {{10}^{22}}V/m\]


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