NEET Sample Paper NEET Sample Test Paper-78

  • question_answer
    A hollow cylinder has a charge q within it. If \[\phi \] is the electric flux in unit of voltmeter associated with the curved surface B, the flux linked with the plane surface A in unit of voltmeter will be

    A)  \[\frac{1}{2}\left( \frac{q}{{{\varepsilon }_{0}}}-\phi  \right)\]                 

    B)  \[\frac{q}{2\,{{\varepsilon }_{0}}}\]

    C)  \[\frac{\phi }{3}\]                                 

    D)  \[\frac{q}{\,{{\varepsilon }_{0}}}-\phi \]

    Correct Answer: A

    Solution :

    By Gauss?s Law \[{{\phi }_{total}}=\frac{q}{{{\varepsilon }_{0}}}\] Let flux corresponding to A B and C is \[{{\phi }_{A}},\,\,{{\phi }_{B}}\,\,and\,\,\phi C\] From symmetry of the figure \[{{\phi }_{C}}={{\phi }_{A}}\] \[\Rightarrow \] Now we can write \[{{\phi }_{total}}={{\phi }_{A}}+{{\phi }_{B}}+{{\phi }_{C}}\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\,2{{\phi }_{A}}+\phi =\frac{q}{{{\varepsilon }_{0}}}\,\,\,\,\Rightarrow \,\,\,{{\phi }_{A}}=\frac{1}{2}\,\left( \frac{q}{{{\varepsilon }_{0}}}-\phi  \right)\]


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