The capacitance of a spherical condenser whose inner sphere is grounded is $1 \mu \mathrm{F}$. If the spacing between the two spheres is $1 \mathrm{mm}$, then what is the radius of the outer sphere?

The graph shows the variation of voltage $V$ across the 

plates of two capacitors $A$ and $B$ with charge $Q$.

Which of the two capacitors has larger capacitance?

For flash pictures, a photographer uses a $30 \mu \mathrm{F}$ capacitor and a charger that supplies $3\times {10}^3 \mathrm{volt}$. Calculate the charge and the energy spent for each flash.

Two capacitors $C_1$ and $C_2$ have an equal amount of energy stored in them. What is the ratio of potential differences across their plates?

A parallel plate capacitor has rectangular plates with dimensions $6.0 \mathrm{cm}\times 8.0 \mathrm{cm}$. If the plates are separated by a sheet of Teflon $\left(K=2.1\right)$ $1.5 \mathrm{mm}$ thick, how much energy is stored in the capacitor when it is connected to a $12 \mathrm{V}$ battery?

The capacity and the energy stored in a parallel plate condenser with air between its plates are, respectively, $C_0$ and $W_0$. If the air between the plates is replaced by the glass (dielectric constant$=5$). Find the capacitance of the condenser and the energy stored in it.

A capacitor of capacitance $10 \mu \mathrm{F}$ is connected to battery of emf $20 \mathrm{V}$. Without disconnecting the source a dielectric ($K=4$) is introduced to fill the space between the two plates of the capacitor. Calculate the charge before the dielectric was introduced.