NEET Sample Paper NEET Sample Test Paper-24

  • question_answer
    The electric field in a certain region is acting radially outward and is given by \[E=Ar.\]A charge contained in a sphere of radius 'a' centred at the origin of the field will be given by

    A) \[4\pi {{\varepsilon }_{0}}A{{a}^{2}}\]           

    B)  \[4{{\varepsilon }_{0}}{{a}^{2}}\]

    C) \[4\pi {{\varepsilon }_{0}}A{{a}^{3}}\]           

    D)  \[{{\varepsilon }_{0}}A{{a}^{2}}\]

    Correct Answer: C

    Solution :

     Let charge enclosed in the sphere of radius is q. According to Gauss theorem, \[\oint{\vec{E}.\vec{d}s}=\frac{q}{{{\varepsilon }_{0}}}\Rightarrow E.4\pi {{r}^{2}}=\frac{q}{{{\varepsilon }_{0}}}\] We are given E = Ar, substituting this value in the above equation we get \[4\pi A{{r}^{3}}=\frac{q}{{{\varepsilon }_{0}}}\]                    (i) If\[r=a,\]then substituting the value in equation (i), we get\[q=4\pi {{\varepsilon }_{0}}A{{a}^{3}}\]


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