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
> are.  
> Charles Brush
I have to agree here too. To degauss the AC must swing equally in both directions,
diminishing very slowly in terms of the frequency, think of this as a very high Q.
If the AC signal damps in only a few cycles, Q ~ 10, then energy must be deposited
in one direction and degaussing will not occur. 
Just thinking out loud.
Dave Huffman