If the charge on a capacitor is increased by $2C$, the energy stored in it increases by $44 \%$. The original charge on the capacitor is (in $C$ )

As in figure shown, if a capacitor $C$ is charged by connecting it with resistance $R$, then energy is given by the battery will be

Three capacitors of capacitances $25 \mu \mathrm{F}, 30 \mu \mathrm{F}$ and $45 \mu \mathrm{F}$ are connected in parallel to a supply of $100$

$V$. Energy stored in the above combination is $\mathrm{E}$. When these capacitors are connected in series to the same supply, the stored energy is $\frac{9}{\mathrm{x}} \mathrm{E}$. The value of $x$ is___________.

A parallel plate capacitor is charged fully by using a battery. Then, without disconnecting the battery, the plates are moved further apart. Then,

If $E$ is the electric field intensity of an electrostatic field, then the electrostatic energy density is proportional to

A sphere of radius $1\,cm$ has potential of $8000\,V$, then energy density near its surface will be