$A$ spherical shell of radius $6 \ cm$ is placed concentrically with a sphere of radius $4 \ cm$. The outer spherical shell is grounded. If the potential of the inner sphere is $3 \ e.s.u.$,what is the charge on it in $e.s.u.$?

If $V_{A}-V_{B}=7 \text{ V}$,then find the stored energy in $C_1$.

Five capacitors together with their capacitances are shown in the adjoining figure. The potential difference between the points $A$ and $B$ is $60\, V$. The equivalent capacitance between the points $A$ and $B$ and the charge on the $5\, \mu F$ capacitor will be respectively:

In the given circuit,the charge $Q_2$ on the $2 \ \mu F$ capacitor changes as $C$ is varied from $1 \ \mu F$ to $3 \ \mu F$. $Q_2$ as a function of '$C$' is given properly by:

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 $V$)

$A$ combination of capacitors is set up as shown in the figure. The magnitude of the electric field,due to a point charge $Q$ (having a charge equal to the sum of the charges on the $4 \mu F$ and $9 \mu F$ capacitors),at a point distance $30 \ m$ from it,would equal ....... $N/C$.