BHU PMT BHU PMT (Mains) Solved Paper-2005

  • question_answer

    Directions: In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:

    A parallel plate air capacitor is connected to a battery. The quantities charge, voltage, electric field and energy associated with the capacitor are given by\[{{Q}_{0}},{{V}_{0}},{{E}_{0}}\]and\[{{U}_{0}}\] respectively. A dielectric slab is now introduced to fill the space between the plates with the battery still in connection. The corresponding quantities now given by Q, V, E and U related to the previous one as: (1) \[Q>{{Q}_{0}}\]                          (2)\[V>{{V}_{0}}\] (3) \[E>{{E}_{0}}\]                            (4)\[U>{{V}_{0}}\]

    A)  1 and 2 are correct

    B)  2 and 3 are correct

    C)  1 and 4 and correct

    D)  1, 2 and 4 are correct

    Correct Answer: C

    Solution :

                     When dielectric slab is introduced capacity gets increased\[\left( C=\frac{K{{\varepsilon }_{0}}A}{d} \right),\]while potential difference remains unchanged. \[\therefore \]                  \[V={{V}_{0}},C>{{C}_{0}}\] Again,                   \[Q=CV\] \[\therefore \]                  \[Q>{{Q}_{0}}\] and                        \[U=\frac{1}{2}C{{V}^{2}}\] \[\therefore \]                  \[U<{{U}_{0}}\] Also,\[E=\frac{V}{d}\]but E and d both are unchaged. Therefore,      \[E={{E}_{0}}\]


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