In lightning storms, the potential difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of thunderclouds are typically 1500 m above the Earth, and can have an area of 110 km². Modeling the Earth–cloud system as a huge capacitor, calculate the capacitance of the Earth–cloud system,

A parallel plate capacitor consists of two plates of area $A$ separated by a distance $d$ and filled with a dielectric of permittivity $\epsilon$. Which of the following gives the correct expression for its capacitance?

Two circular plates of radius 2cm are brought together so their separation is 5mm. What is the capacitance of these plates?

A 3 F capacitor is given a potential difference across its plates of 10 V. What is the charge built up on its plates? If the source of the potential difference across the plates is removed, but the plates maintain their charge, what is the new potential difference across the capacitor if the distance between the plates is doubled?