JEE Main & Advanced Physics Electrostatics & Capacitance Question Bank Critical Thinking

  • question_answer
    Two condensers of capacities \[2C\] and C are joined in parallel and charged upto potential V. The battery is removed and the condenser of capacity C is filled completely with a medium of dielectric constant K. The p.d. across the capacitors will now be                          [IIT 1988]

    A)                    \[\frac{3V}{K+2}\]

    B)                                      \[\frac{3V}{K}\]

    C)                    \[\frac{V}{K+2}\]        

    D)            \[\frac{V}{K}\]

    Correct Answer: A

    Solution :

     \[{{q}_{1}}=2CV,\] \[{{q}_{2}}=CV\] Now condenser of capacity C is filled with dielectric K, therefore C2 = KC As charge is conserved \ \[{{q}_{1}}+{{q}_{2}}=(C_{2}^{'}+2C)V'\] Þ \[V'=\frac{3CV}{(K+2)C}=\frac{3V}{K+2}\]


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