[Amps] 240V Outlet

[Jim Brown]

>I dont understand the last paragraph. If the neutral and ground are in 
>parallel and conneted to identical points in the panel and equipment where 
>does this field come from?

In a properly wired circuit, current from the hot (phase) conductor returns 
on the neutral, so all of the associated magnetic field is contained 
entirely in the region between and immediately around those two conductors. 
The currents, and thus the fields, are equal and opposite, so there's no 
external field.  But when there is an extra bond between neutral and 
ground, the return current divides by Ohm's law between neutral and those 
other ground paths, and much of it returns on parallel ground paths ("the 
building"). Only the fraction of the current returning on the neutral 
cancels field from the phase conductor, AND the fraction of current 
returning on the building forms a large inductive loop, and thus a strong 
field (field is proportional to loop area). 

There are drawings that show this in the Ham Interfacing power point. 
They're midway through it, in the part where I'm talking about magnetically 
induced hum. 

http://audiosystemsgroup.com/HamInterfacing.pdf 

73,

Jim K9YC