I helped my grandpa install a light fixture in his kitchen(he's in the process of remodeling) and noticed the wiring was a little weird. The wiring is going from the fixture to the switch which I thought, and a google search confirmed, is supposed to go like this:
However, this is how the existing fixture was wired and how my grandpa insists I wire the new fixture:
The wiring diagram at the top of this page belongs to do-it-yourself-help.com. The original can be found here: https://www.do-it-yourself-help.com/wiring_switches.html
I'm not good with diagrams, but whats happening is the hot is coming from the breaker box(the neutral too, but it's ignored) going into the fan, and then out of the fan to the switch. The switch is then sent to neutral on the breaker box.
He's going to be due for an inspection once all the wiring is done and I'm concerned about this. The guy who did his wiring said he did all rooms like this. This area is under NEC 2005
Best Answer
What is being created is a "switched neutral," which is not proper and not allowed according to the NEC. It's possible, but highly unusual, to run the hot through the switch instead of the neutral and create a switched hot with a separate neutral path back to the breaker. That would be better than a switched hot, but may still be disallowed by NEC and I would never encourage anyone to wire a fixture that way either. The wiring shown in your first diagram, or wiring that runs the line to the switch first and switches the hot there, are the proper methods to wire a switched light.