A parallel plate air capacitor has capacitance $C_P$. It is equally filled with parallel layers of materials of dielectric constants $\mathrm{K}_1$ and $\mathrm{K}_2$. Now its capacity becomes $C_K$. The ratio $C_P$ to $C_K$ is

A parallel plate capacitor with plate area A and plate separation $d$ is charged by constant current $I$. A plane surface of area $\frac{\mathrm{A}}{2}$, parallel to the plates is drawn simultaneously between the plates. The displacement current through this area is

Two parallel plate air c apacitors of same capacity ' C ' are connected in parallel to a battery of e.m.f. ' $E$ '. Then one of the capacitors is completely filled with dielectric mnaterial of constant ' K '. The change in the effective capacity of the parallel combination is