[Gllug] Electric Shocks

[Pete Ryland]

On Fri, May 16, 2003 at 12:04:48PM +0100, t.clarke wrote:
> Since some of you gentlemen are cleary very knowledgable on the subject of
> electicity, maybe someone has the definitive answer to a a couple of questions
> that have fascinated me:
> 
> 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 !

You won't receive a shock but you will become charged, so I would advise
against stepping off the mat, or otherwise grounding onesself, or even going
anywhere *close* to a ground, until you have discharged slowly (play catch
with a grounded person for example).

> 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 ?

If it truly is floating, then touching one of the terminals will indeed not
cause much current to flow through you to ground.  Instead it will "fix" the
voltage.  Hence, it is *not* advised to touch both contacts at once, or to
have one person touching one terminal and someone else touching tother.

Pete

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