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12th Class Physics Electrostatics & Capacitance Question Bank MCQ - Electrostatic Potential and Capacitance

  • question_answer
    Air-filled parallel plate capacitor has a capacitance of 1 nF. The plate separation is then tripled and a dielectric is inserted, completely filling the space between the plates. As a result, the capacitance increases to 5 nF. The dielectric constant of the dielectric is:

    A) 2                     

    B) 3         

    C) 6                     

    D) 9

    Correct Answer: D

    Solution :

    (d) 9 Capacitance of parallel plate capacitor with air \[C=\frac{{{\varepsilon }_{0}}A}{d}\]                            … (1) Capacitance of parallel plate capacitor with dielectric \[C'=\frac{K{{\varepsilon }_{0}}A}{3d}\]                                    … (2) \[\Rightarrow \,\,\,\,\frac{C'}{C}=\frac{K{{\varepsilon }_{0}}A}{3d}\times \frac{d}{{{\varepsilon }_{0}}A}\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\frac{3}{1}=\frac{K}{3}\Rightarrow K=9\]


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