A parallel plate capacitor has circular plates of $10\, cm$ radius separated by an air-gap of $1\, mm$ . It is charged by connecting the plates to a $100\, volt$ battery. Then the change in energy stored in the capacitor when the plates are moved to a distance of $1\, cm$ and the plates are maintained in connection with the battery, is

  • A

    Loss of $12.5\, ergs$

  • B

    Loss of $125\,ergs$

  • C

    Gain of $125\, ergs$

  • D

    Gain of $12.5\, ergs$

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