Sorry to answer these out of order....
5) Open core,Closed core,Shell core.Reference...sorry,it's from an electrical exam preparation guide I have with no cover:( Someone copied it for me in a loose leave binder a few years ago.
1)Higher.In doing so,any weaknesses will be revealed at a higher percentage than if the same voltage was used.Same reference.
2)NEC 2005 110.19
4)I'm in NEC 2005......408.34 through 408.36. Looks like ther are some CHANGES in this from when I found the EXCACT question in the book I mentioned in the first 2 questions.
3)NEC 2005......470.18(b)
