From: SFPhysics@aol.com
Date: Tue Apr 13 2004 - 01:57:45 PDT
From: SFPhysics@aol.com Message-ID: <da.7f01090.2dad0589@aol.com> Date: Tue, 13 Apr 2004 04:57:45 EDT Subject: Van de Graaff discharge through humans
I noticed that my Van de Graaf generator, when it
discharges, can turn the TV on and off across the room
and restarts the computer on my desk. What does that
mean it could do to biological systems like the brain
or internal devices like pace makers...does anyone
know?
Thanks,
Debbie
Greetings Debbie:
The Van de Graaff (Robert Van de Graaff) generator can deliver a large
discharge depending on the size of the collecting sphere. Spheres less than 22"
diameter (approx. 56 cm) cannot get up to the stored energy level of 10 joules
which is the threshold of being dangerously hazardous to humans. Still the
smaller collecting spheres can deliver a nasty shock which would be dangerous to
anyone with a pacemaker or a history of heart arrhythmia. The current path for
the DC discharge is primarily though the blood vessels since blood is a
nicely conducting salt water solution. The brain is somewhat insulated by the
cranium so most charges do not find an easy pathway there. Repeated shocks do
have some detrimental physiological effects on nerve endings but again this is
with larger currents and sustained currents along nerve paths. Electricity is
most dangerous when the current is high and is sustained. The short discharges
from a school lab sized VdG to most people is just a short unpleasant
experience. Primarily the damage is done at the point of discharge on the skin where
local nerve endings feel the greatest effect. The tiny burn is usually only
visible under a microscope. This can be avoided by holding a large metal
object as a discharge electrode so that the charge is not concentrated when you
want to play Dr. Frankenstein!
Hope that answers your question.
Best wishes to the list,
Al Sefl
Who once proved that the school phone system needed a better ground
connection
when he discharged a 500 kV Van de Graaff through a receiver and killed the
solid state system completely...
And, it was the last time anyone ever interrupted him in the middle of a
demonstration...
From then on phone calls were only put through to the Physics Lab during
passing periods... ;-)
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