At 06:22 PM 12/10/97 EST, you wrote:
>In a message dated 97-12-10 14:14:07 EST, you write:
>
><< >With a sensitive instrumentation amp you can measure the voltage
> difference >between your feet and your head (usually a couple hundred volts
> over six feet).
>
> This is really interesting!
>
> But if it's a couple of hundred volts, why do you need a sensitive
> instrument amp?
>
> Bruce
>  >>
>Also, if this is true (now that we are thinking about it) why do we not
notice
>it in this case, but if we put a 115V mains on our head and stood on a copper
>pipe to earth we would be paramedic material??
>

Hi Mark,

The reason why we are not harmed by this electric field gradient is that ,
as someone else mentioned before, the current involved is so low. The
voltage comes from just a few electrons difference in charge, separated by
a very good insulator. If we bridge the gap, only a tiny current flows. It
is sort of like a static discharge which occurs when one walks  accross a
carpet and touches a doorknob. The charge transfer is bearly enough for you
to feel it (or sometimes, it is quite enough for you to feel it, but it is
for such a short duration that it does you no harm). In fact, the voltages
involved in these little shocks gotten by touching a door knob can easily
be in the megavolts, or so I have read.

Sean

+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
+--------------------------------+
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