In between the plates of parallel plate capacitor of plate separation 'd' a dielectric plate of thickness ' $t$ ' is inserted. The capacitance becomes one-third of the original capacity without dielectric. The dielectric constant of the plate is

A parallel combination of two capacitors of capacities ' C ' and ' $\frac{\mathrm{C}}{3}$, respectively is connected across a battery of 12 volt. When both capacitors are fully charged, the charge and energy stored in them is $Q_1, Q_2$ and $E_1, E_2$ respectively. Then the ratio of $\left(E_1-E_2\right)$ to $\left(Q_1-Q_2\right)$ is