Answer
$E=66\mu J$
Work Step by Step
We can determine the energy stored is:
$E=\frac{1}{2}CV^2$...eq(1)
We also know that
$C=\frac{kA\epsilon_{\circ}}{d}$
Thus, we plug in the known values to obtain:
$C=\frac{5.5(0.034)(8.85\times10^{-12})}{2\times10^{-3}}=827.475\times10^{-12}$
Now, we have to find $V$
As $V=Ed$, where $E$ represents electric field
We find: $V=200\times10^3(2\times10^{-3})=400V$
Now putting values in eq(1), we get
$E=\frac{1}{2}(827.475\times10^{-12})(400)^2=6.6\times10^{-5}=66\times10^{-6}=66\mu J$
$E=66\mu J$
