J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    A capacitor is charged by a battery and the energy stored is U. The battery is now removed and the separation distance between the plates. is doubled. The energy stored now is

    A)  \[\frac{U}{2}\]                

    B)  \[U\]

    C)  \[2\,\,U\]           

    D)  \[4\,\,U\]

    Correct Answer: C

    Solution :

    Energy stored \[U=\frac{1}{2}qV\] As the distance d is increased between the two plates. Now, stored energy, \[U'=\frac{1}{2}qV'\] \[=\frac{1}{2}q\left[ \frac{q}{C} \right]\] \[=\frac{1}{2}\frac{{{q}^{2}}d}{{{\varepsilon }_{0}}A}\] \[U\propto d\] Hence,-       \[U'=2U\]


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