Field of NoThingness - spl BiNal

A thundercloud and the earth can be regarded as a parallel plate capacitor. Taking the area of the thundercloud to be $50 \;km^2$, its height above the earth as $1\; km$ and it's potential $100\; KV$, calculate the energy stored.

Two spheres of radii $5\; cm$ and $10\;cm$ are given charges $100\;C$ and $50\;C$ respectively and then connected by a wire. Calculate the loss of energy after connection.

A parallel plate air capacitor has a capacitance of $10^{-9} \; F$. What potential difference is required for a charge of $5 * 10^{-5}\;C$ ? What is the total energy stored in it?

A parallel plate capacitor with air as the dielectric has a capacitance of 6∗10−4μF and is charged by a 100V battery. Calculate the charge and the energy stored in the capacitor.

A 300V battery is connected across capacitors of 3μF and 6μF in parallel. Calculate the energy stored in each capacitor.