In the given circuit, what are the potential differences between points $A$ and $B$ $(V_{AB})$ and between points $B$ and $C$ $(V_{BC})$?

Find the charge on the capacitor $C$ in the following circuit in $\mu C$.

$A$ parallel plate capacitor of capacitance $2\; F$ is charged to a potential $V$. The energy stored in the capacitor is $E_1$. The capacitor is now connected to another uncharged identical capacitor in parallel combination. The energy stored in the combination is $E_2$. The ratio $E_2 / E_1$ is

$A$ capacitor of unknown capacity is connected across a battery of $V$ volt. The charge stored in it is $Q$ coulomb. When the potential across the capacitor is reduced by $V_1$ volt,the charge stored in it becomes $Q_1$ coulomb. The potential $V$ is

Condenser $A$ has a capacity of $15\,\mu F$ when it is filled with a medium of dielectric constant $15$. Another condenser $B$ has a capacity of $1\,\mu F$ with air between the plates. Both are charged separately by a battery of $100\,V$. After charging,both are connected in parallel without the battery and the dielectric medium being removed. The common potential now is.....$V$

Find the equivalent capacitance between $A$ and $B$.