For the given circuit,find the charge on the $4\ \mu F$ capacitor in $\mu C$.

$A$ source of potential difference $V$ is connected to the combination of two identical capacitors as shown in the figure. When key $K$ is closed,the total energy stored across the combination is $E_{1}$. Now key $K$ is opened and a dielectric of dielectric constant $K_{d} = 5$ is introduced between the plates of both capacitors. The total energy stored across the combination is now $E_{2}$. The ratio $E_{1} / E_{2}$ will be:

Charge on the capacitor in the given circuit in steady state condition is :- ............... $\mu C$

Find the potential difference $V_a - V_b$ between the points $a$ and $b$ shown in the figure.

In the given circuit, if point $C$ is connected to the earth and a potential of $+2000 \, V$ is applied to point $A$, the potential at point $B$ is.....$V$.

Each of the $N$ small drops has a radius $r$ and is charged to a potential $V$. If these drops coalesce to form a single large drop,what is the potential of the large drop?