A parallel plate capacitor of plate area $A$ and plate seperation $d$ is charged to potential difference $V$ and then the battery is disconnected. Aslab of dielectric constant $K$ is then inserted between the plates of the capacitor so as to fill the space between the plates. If $Q, E$ and $W$ denote respectively, the magnitude of charge on each plate, the electric field between the plates (after the slab is inserted) and the work done on the system, in question, in the process of inserting the slab, then 

  • A

    $Q$ = $\frac{{{\varepsilon _0}AV}}{d}$

  • B

    $W =$ $- $ $\frac{{{\varepsilon _0}A{V^2}}}{{2\,d}}\,\left( {1 - \frac{1}{K}} \right)$

  • C

    $E $ $=$  $\frac{V}{{K\,d}}$

  • D

    all of the above

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