[Gllug] Electric Shocks

[Chris Bell]

On Fri 16 May, t.clarke wrote:

> 
> a) is it true that if you stand on a perfect or near-refect insulator (eg big
> fat rubber mat) and touch an HV source (say several KV relative to earth) you
> won't get a shock ?   - not the sort of thing I wish to test practically !
> 
> b) we operate a 240V UPS here which 'floats'  - ie one leg is NOT tied down
> to earth.  The suggestion is similarly that touching either wire will not
> produce a shock since there is supposedly nowhere for the current to flow.
> True or false ?
> 
   A capacitor is produced when two conductors are separated by an
insulator. The total electric charge stays constant, but the insulator
physically distorts as large numbers of negatively charged electrons are
dragged towards the positively charged conductor, and there is a
corresponding movement of charge through the conductors. The distance may be
minute, but this movement of charge is a real electric current which
increases as the rate of change of voltage increases and separation is
reduced, so you may feel it if it is high frequency AC or a sudden large
change of DC voltage. An isolated or floating voltage has no loop connection
apart from any stray capacitance, so the current should be small.

-- 
Chris Bell



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