Assuming the drops to be spherical,$27$ identical drops of mercury are charged simultaneously to the same potential of $20 \ V$. If all the charged drops are made to combine to form one big drop,then the potential of the big drop will be: (in $V$)

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

$A$ parallel plate capacitor has capacitance $C$. If the charges on the plates are $Q$ and $-3Q$,find the potential difference between the plates.

Two parallel plate capacitors of $8 \mu F$ each are connected in parallel to a $10 \ V$ battery. The plate separation in one of the capacitors is reduced to $40 \%$ of its initial value. The increase in the total charge stored on the capacitors is

$A$ capacitor of capacity $C$ is connected to a battery of potential $V$ in parallel. The distance between its plates is reduced to half at once,while the battery remains connected. Then,the energy supplied by the battery to charge the capacitor to potential $V$ again is:

$A$ body of mass $1 \,g$ and carrying a charge $10^{-8} \,C$ passes through two points $P$ and $Q$. $P$ and $Q$ are at electric potentials $600 \,V$ and $0 \,V$, respectively. The velocity of the body at $Q$ is $20 \,cm/s$. Its velocity in $m/s$ at $P$ is: