CMC Medical CMC-Medical VELLORE Solved Paper-2010

  • question_answer
    Capacitance of a capacitor becomes \[\frac{4}{3}\] times its original value, if a dielectric slab of thickness, t = \[\frac{d}{2}\] is inserted between plates (d = separation between the plates) The dielectric constant of the stab is

    A)  6                                            

    B)  8

    C)  4                                            

    D)  2 S

    E)  None of these

    Correct Answer: D

    Solution :

                    Original capacity, \[{{C}_{0}}=\frac{{{\varepsilon }_{0}}A}{d}\] On introducing dielectric slab of thickness \[\frac{d}{2}\]the capacity becomes \[C=\frac{{{\varepsilon }_{0}}A}{\left( d-\frac{d}{2} \right)+\frac{d}{2K}}=\frac{{{\varepsilon }_{0}}A}{\frac{d}{2}\left( 1+\frac{1}{K} \right)}\] As,          \[C=\frac{4}{3}{{C}_{0}}\] \[\therefore \] \[\frac{{{\varepsilon }_{0}}A}{\frac{d}{2}\left( 1+\frac{1}{K} \right)}=\frac{4}{3}\frac{{{\varepsilon }_{0}}A}{d}\] or            \[1+\frac{1}{K}=\frac{3}{2}\] or            \[k=2\]


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