Total chare of the system \(=\mathrm{CV}+\mathrm{nCV}\)
\(=(n+1) C V\)
After the insertion of dielectric of constant \(\mathrm{K}\) New potential (common) \(\mathrm{V}_{\mathrm{c}}=\frac{\text { Total charge }}{\text { Total capacitance }}\)
\(=\frac{(n+1) C V}{K C+n C}=\frac{(n+1) V}{K+n}\)
$\left(\frac{1}{4 \pi \epsilon_{0}}=9 \times 10^{9} Nm ^{2} / C ^{2}\right)$