Minimum number of $2\,\mu F$ and $250\, V$ capacitors required to make a combination of $12\,\mu F$ and $500\, V$ is:

Capacitor $A$ has a capacitance of $1\ \mu F$. It is filled with a dielectric medium of constant $K = 15$. Another capacitor $B$ has a capacitance of $1\ \mu F$. Both are charged separately by $100\ V$ batteries. After charging,the batteries are removed,the dielectric is removed from $A$,and the capacitors are connected in parallel. Calculate the common potential in $V$.

$A$ parallel plate capacitor,after being charged,is kept connected to a battery,and the plates are pulled apart with the help of insulating handles. Which of the following quantities will decrease?

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

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 $V$)

$A$ soap bubble of radius $R$ and surface tension $T$ is formed in a vacuum. It is slowly charged so that it slowly expands. It stops charging when the radius becomes $2R$. Find the amount of charge given to the bubble.