The capacitance of the earth, viewed as a spherical conductor of radius $6408 \mathrm{km}$ is

The energy stored in a capacitor is in the form of

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

Three plates $A,B,C$ each of area $50 {\mathrm{cm}}^2$ have separation $3 \mathrm{mm}$ between $A$ and $B$ and $3 \mathrm{mm}$ between $B$ and $C$. The energy stored when the plates are fully charged is