JEE Main & Advanced Sample Paper JEE Main Sample Paper-27

  • question_answer
    A hollow cylinder has a charge q coulomb at the centre within it. If ([) 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 :

    According to Gauss's law, \[{{\phi }_{total}}\,=\frac{\theta }{{{\varepsilon }_{0}}}\] Let electric flux linked with surfaces A, B and C are \[{{\phi }_{A}},\] \[{{\phi }_{B}}\] and \[{{\phi }_{C}}\] respectively That is \[{{\phi }_{total}}\,={{\phi }_{A}}+{{\phi }_{B}}+{{\phi }_{C}}\] \[{{\phi }_{C}}={{\phi }_{A}}\] \[2{{\phi }_{A}}={{\phi }_{_{total}}}\,=\frac{q}{{{\varepsilon }_{0}}}\] Or \[{{\phi }_{A}}=\frac{1}{2}\,\left( \frac{q}{{{\varepsilon }_{0}}}\,-{{\phi }_{B}} \right)\] But \[{{\phi }_{B}}=\phi \] (given) \[{{\phi }_{A}}=\frac{1}{2}\left( \frac{q}{{{\varepsilon }_{0}}}-\phi  \right)\]


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