$A$ $4\ \mu F$ capacitor is charged to $80\ V$ and a $6\ \mu F$ capacitor is charged to $30\ V$. When they are connected together,the energy lost by the $4\ \mu F$ capacitor is ..... $mJ$.

$A$ circuit shown in the figure consists of a battery of $emf$ $10\,V$ and two capacitors $C_1$ and $C_2$ of capacitances $1.0\,\mu F$ and $2.0\,\mu F$ respectively. The potential difference $V_A - V_B$ is $5\,V$. Which of the following statements is correct?

$A$ series combination of $N_1$ capacitors (each of capacity $C_1$) is charged to a potential difference $3V$. Another parallel combination of $N_2$ capacitors (each of capacity $C_2$) is charged to a potential difference $V$. The total energy stored in both combinations is the same. The value of $C_1$ in terms of $C_2$ is:

The dielectric strength of air is $E = 3 \times 10^6 \ V/m$. What is the maximum charge that can be given to a sphere of diameter $6 \ m$? (in Coulombs)

Identify the correct statements:
$A$. Effective capacitance of a series combination of capacitors is always smaller than the smallest capacitance of the capacitor in the combination.
$B$. When a dielectric medium is placed between the charged plates of a capacitor, displacement of charges cannot occur due to the insulation property of the dielectric.
$C$. Increasing the area of the capacitor plate or decreasing the thickness of the dielectric is an alternate method to increase the capacitance.
$D$. For a point charge, concentric spherical shells centered at the location of the charge are equipotential surfaces.
Choose the correct answer from the options given below.

Consider two charged metallic spheres $S_{1}$ and $S_{2}$ of radii $R_{1}$ and $R_{2},$ respectively. The electric fields $E_{1}$ (on $S_{1}$) and $E_{2}$ (on $S_{2}$) on their surfaces are such that $E_{1} / E_{2} = R_{1} / R_{2}.$ Then the ratio $V_{1} / V_{2}$ of the electrostatic potentials on each sphere is: