Besides irrotation incompressible flow, list 3 physical processes governed by Laplace equation. (feel free to list more, they're a bonus)
1. One sentence description of the process (what is it),
2.Identify variable that is being solved by the Laplace equation, together with units of this variable,
3.Identify source where information is found, and 4. a citation to a book or a journal article where process is mentioned (Wikipedia or similar web links do not count).