Physics - Capacitor Question with Solution | TestHub

Here, $C=9\mathrm{nF},{\epsilon }_r=2.4,V=20$ volt Dielectric strength $=20\mathrm{MV}{\mathrm{m}}^{-1}$ Let separation between plates $=d$ $\begin{array}{rl}& E=\frac{V}{d}\Rightarrow 20\times 10^6=\frac{20}{d}\\ & d=10^{-6}\mathrm{m}\end{array}$ Now, $C=\frac{{\epsilon }_{0}A{\epsilon }_r}{d}$ $\begin{array}{rl}& 9\times 10^{-9}=\frac{8.85\times 10^{-12}\times A\times 2.4}{10^{-6}}\\ & A=\frac{9\times 10^{-15}}{8.85\times 2.4\times 10^{-12}}=4.2\times 10^{-4}{\mathrm{m}}^2\end{array}$