[TenTec] Induction Field [WAS - PS grounding]

[David McClafferty]

To induce a current into a conductor the magnetic
field must be varying or the conductor or field must
be moving. The magnetism in an MRI machine is steady,
so unless they wheeled you in there quite fast, you
wouldn't get much current induced into your body.
I found an interesting website that describes how an
MRI machine works. 
http://www.howstuffworks.com/mri.htm

73, Dave, VE1ADH
 
 --- tongaloa <tongaloa at alltel.net> wrote: > Pete-
> 
> OK
> But I still don't understand how enough EMF can be
> generated to cause 
> problems.
> 
> I'm probably confused by the ratings they use on MRI
> machines.
> When I'm in the MRI machine and it's a 0.5T field
> (according to the
> operator) does he really mean 0.5T/s or does he mean
> the maximum field 
> strength is 0.5T
> which at MRI operating frequencies is lots more than
> the 0.02T field 
> strength at a meter
> from a pretty good sized, real, lightning bolt.
> 
> If the lightning bolt takes 10 microseconds to go
> from 'small' to 'full' 
> current then
> it's roughly 200T/s which would produce a LOT more
> EMF than a 0.5T/s MRI...
> I don't know MRI operating frequency but at 500kHz
> it would be roughly 
> 500T/s
> if the 0.5T (operator number) is the max. (I think
> 500kHz is abotu 
> right??? Any MRI
> ops out there?)
> 
> I didn't croak in the MRI machine and I was there
> for an hour ;-)
> 
> 73,
> -Bob
> 
> 
> 
> 
> ac5e at comcast.net wrote:
> 
> >Bob, an induction field is an induced current, or
> voltage, resulting from current flow. Lotsa current
> equals lotsa induction field. Which, according to
> the local street preacher, is often followed by
> checking out a harp and wings. 
> >
> >The human body is essentially a high resistance one
> turn inductor. In lab testing during the 1950's more
> than 5 Kv at 10 A was measured in a cadaver near a
> lab lightning stroke. And lab lightning is a very
> mild cousin to the wild lightning generated in a
> thunderstorm. Do not put your unshielded self or
> anything you value near anything that will attract
> the wild stuff. 
> >
> >And I forgot who asked, but yes, your rotor cables
> need to be lightning arrestored, grounded, and
> anything else that can be done to keep the big
> sparks away. 
> >
> >73  Pete Allen AC5E
> >
> >
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> >
> 
> 
> 
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