I got the call that when they turned on the coach light the breaker would trip. I found out why after I cut a hole in the drywall and found the problem. The house next door was burnt by arson, and the builder paid somebody to fix this already. This house never caught on fire. The drywall was never pulled down to inspect any of the wiring behind it.
There has been a lot of heat in there, looking at the indepth burning of the wood. Amazing that the particular circuit didn't have problems before. From the corrosion on the copper wires, there must have been some moisture in that wall space too.
The product of rotation, excitation and flux produces electricty.