Clouds
Clouds are a composition of many forms of water, for example it is composed of tiny water droplets, and ice crystals. Where there are various sizes of these naturally formed "water masses" as I like to calls them. The clouds in the picture below shows some of the more common clouds that we see. The more interesting clouds are cumulonimbus because they are the lightning bearing clouds.
"Lighting originates when wind updrafts and downdrafts take place in the atmosphere, creating a charging mechanism that separates electric charges in clouds – leaving negative charges at the bottom and positive charges at the top. On the ground the negative charges at the bottom of the clouds push the negative charges away from the surface, the only charges remaining on the surface are the positive charges. This is known as charging by induction." -Derek Owens
Mathematically this concept is represented by gausses law, where the charge is subject to change due to the type of surface it is. If the radius is bigger the electric force will be smaller, so it is indirectly proportional to the charge on on the surface.
