In the circuit shown,each capacitor has a capacitance $C$. The emf of the cell is $E$. If the switch $S$ is closed:

When two identical capacitors are charged individually to different potentials and then connected in parallel,after disconnecting from the source . . . . . .

Consider an evacuated cylindrical chamber of height $h$ having rigid conducting plates at the ends and an insulating curved surface as shown in the figure. $A$ number of spherical balls made of a light weight and soft material and coated with a conducting material are placed on the bottom plate. The balls have a radius $r \ll h$. Now a high voltage source $(HV)$ is connected across the conducting plates such that the bottom plate is at $+V_0$ and the top plate at $-V_0$. Due to their conducting surface,the balls will get charged,will become equipotential with the plate and are repelled by it. The balls will eventually collide with the top plate,where the coefficient of restitution can be taken to be zero due to the soft nature of the material of the balls. The electric field in the chamber can be considered to be that of a parallel plate capacitor. Assume that there are no collisions between the balls and the interaction between them is negligible. (Ignore gravity)
$(1)$ Which one of the following statements is correct?
$(A)$ The balls will stick to the top plate and remain there
$(B)$ The balls will bounce back to the bottom plate carrying the same charge they went up with
$(C)$ The balls will bounce back to the bottom plate carrying the opposite charge they went up with
$(D)$ The balls will execute simple harmonic motion between the two plates
$(2)$ The average current in the steady state registered by the ammeter in the circuit will be
$(A)$ zero
$(B)$ proportional to the potential $V_0$
$(C)$ proportional to $V_0^{1/2}$
$(D)$ proportional to $V_0^2$

$(a)$ Determine the electrostatic potential energy of a system consisting of two charges $7 \; \mu C$ and $-2 \; \mu C$ (with no external field) placed at $(-9 \; cm, 0, 0)$ and $(9 \; cm, 0, 0)$ respectively.
$(b)$ How much work is required to separate the two charges infinitely away from each other?
$(c)$ Suppose that the same system of charges is now placed in an external electric field $E = A(1/r^2)$; $A = 9 \times 10^5 \; C \cdot m^{-2}$. What would the electrostatic energy of the configuration be?

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

Three large plates are arranged as shown. How much charge will flow through the key $K$ if it is closed?