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

Consider two identical metallic spheres of radius $R$ each having charge $Q$ and mass $m$. Their centers have an initial separation of $4 R$. Both the spheres are given an initial speed of $u$ towards each other. The minimum value of $u$, so that they can just touch each other is: (Take $k=\frac{1}{4 \pi \epsilon_0}$ and assume $k Q^2 > G m^2$ where $G$ is the Gravitational constant)

What is the effective capacitance between points $X$ and $Y$ in the given circuit? (All capacitors are in $\mu F$)

Three capacitors each having capacitance $C = 2\,\mu F$ are connected with a battery of $e.m.f.$ $30\, V$ as shown in the figure. When the switch $S$ is closed,then select the incorrect statement.

$A$ series combination of $n_1$ capacitors,each of value $C_1$,is charged by a source of potential difference $4V$. When another parallel combination of $n_2$ capacitors,each of value $C_2$,is charged by a source of potential difference $V$,it has the same total energy stored in it as the first combination has. The value of $C_2$ in terms of $C_1$ is:

Consider the circuit shown in the figure below. All the resistors are identical. The charge stored in the capacitor,once it is fully charged is