$A$ spherical drop of mercury having a potential of $2.5\, V$ is obtained as a result of merging $125$ droplets. The potential of constituent droplets would be........$V$

Two identical capacitors are joined in parallel,charged to potential $V$,separated and then connected in series,$i.e.$,the positive plate of one is connected to the negative plate of the other. Then

$A$ composite parallel plate capacitor is made up of two different dielectric materials with different thicknesses ($t_{1} = 0.5 \text{ mm}$ and $t_{2} = 1 \text{ mm}$) and dielectric constants ($\epsilon_{r1} = 3$ and $\epsilon_{r2} = 4$) as shown in the figure. The two dielectric materials are separated by a conducting foil $F$. The voltage of the conducting foil is $.....V$.

Five capacitors are connected to a $DC$ potential of $100\,V$ as shown in the figure. Find the charge in the $10\,\mu F$ capacitor (top-left).

The figure shows a diagonal symmetric arrangement of capacitors and a battery. The potentials of the points $B$ and $D$ are:

$A$ capacitor is made of two circular plates of radius $R$ each,separated by a distance $d \ll R$. The capacitor is connected to a constant voltage $V$. $A$ thin conducting disc of radius $r \ll R$ and thickness $t \ll r$ is placed at the center of the bottom plate. Find the minimum voltage required to lift the disc if the mass of the disc is $m$.