Re: Magnetization of Toroid

>The AC should never magnetize anything.  Too 
>the contrary, this is a perfect demagnetizer current.  DC can magnetize 
>ferromagnetic material very well.  The DC currents from the "charging ion 
>clouds" should be too small to detect with a simple compass anyway. 

A thought: When an AC source is switched off, the alternating domains will stay
aligned to their last position.  An AC tape head demagnetizer can easily
magnetize a head if it is abruptly switched off while in close proximity to the
head.  I used to work in a recording studio here in NY and we had to be very
careful about this with the big expensive 24tr heads.  It seems possible that
when a TC is turned off (variac dialed down), the last discharge through the
spark gap could determine the magnetic polarity.  The wave alternates, but it
is also damped so the initial peak might determine polarity while subsequent
oscillations could lack the energy to further change it much (sort of like the
mechanism in the rectified ion cloud theory...but on a one shot basis).  This
could be a moot point if, as Richard mentioned, the toroid is aluminum as most

Charles Brush