Re: VanderGraaff safety (fwd)

[brian whatcott <inet@INTELLISYS.NET>]

Sam asked three questions.

Low Resistance:
I measured my sinistral index to my dextral index and read about 780 kilohms.
I measured my sinistral index to my wife's dextral index while holding her
other hand. This read about 1.7 megohms.

Resistance of Daisy Chain:
 This value can be expected to vary between quite wide limits. But let us
suppose the children's unit resistance was 800 kilohms, and further, let us
suppose that there were ten of them in a daisy chain.

 Then the series value I describe as 'low' in this context is  8 megohms.
   On the other hand, I consider a 5 kilohm resistor to be a rather
 'high' value when discharging a 1.5 volt cell.

Skin Effect:
Skin effect as usually understood, refers to the increased impedance to
high frequency current caused by confinement of current path to the near
surface.
  But in this context, the effect of moist skin, dramatically reduces the
resistance hand to hand.

Discharge of Capacitive Sources:
The discharge of a capacitor can indeed be a momentary current.
Or it can be a slow discharge.
 The time duration of this current depends on the resistance of the
discharge path. Undoubtedly, a faster, larger current amplitude  occurs in
an 8 megohm path, than in an 8 gigohm path.

Brian


At 13:47 1/5/99 -0500, you wrote:
...
> Low resistance to ground??  What do you think is the resistance of a chain of
> humans connected directly to ground?  Does the skin effect have any
relation to
> this problem?  It is a current spike!
>
> Sam
>
>
> brian whatcott wrote:
....
> >  The current path would have been shared by all his student daisy chain.
> > But some subjects are more susceptible than others.
> > It is better to ensure the current magnitude is limited in one of two ways:
> > 1) Limit the maximal charge if the path to ground is rather low resistance
> > (as here)
> > or
> > 2) Limit the discharge rate by ensuring the ground path is high resistance
> > at all accessible points.
> >
> > Brian
> >
> > > Someone touched the water faucet and they all felt a jolt. One
> > > student came up to me and said his heart felt funny. It was racing
> > > like crazy and I thought it might be fibrillating. ...
brian whatcott <inet@intellisys.net>
Altus OK