"Brian Gaff (Sofa)" wrote in message
...
Yes that would certainly do it. I am very sensitive to that electrostatic
Talking of real life sad cases though, the daughter of an MP had just had
a new kitchen fitted and was trying to get something out of a cupboard
and touched a securing screw with one hand while steadying herself on the
washing machine with the other. She was killed instantly and the kitchen
fitter was convicted of involuntary manslaughter. He had basically joined
a number of wires up inside a wall cavity, and not filled in the hole
merely screwed the cabinet over the top, One of the screws in the back had
just caught a live wire and was thus live and the washing machine was
earthed. The report did not go into too many details, but apparently she
was alone her heart stopped and she fell off her kickstep and hit her head
on some appliance.

That's nasty. And such a stupid mistake for the electrician to make.

Earthed appliances can be more trouble that they are worth if you happen to
touch an appliance that is live.

I got a nasty jolt when I unplugged a TV aerial cable from a USB DVB tuner
connected to my PC. I had the metal aerial plug in one hand and was holding
the earthed case of the PC with the other hand. As soon as the plug was no
longer in contact with the earthed PC, I got about 100 V across me. Probably
very low current, but it was enough to hurt for a few minutes afterwards.
Another leg of the TV aerial was plugged into my TV (which was off but
plugged in) and from there audio and SCART cables went to a VCR, an
OnDigital box and my hifi. One of those was evidently to blame. Having
disconnected everything in turn, with a voltmeter across the aerial plug and
mains earth, I narrowed it down to the TV. It was putting out about 300 V as
measured with a high-resistance voltmeter which went down to about 100 V
when I put a human-sized resistor (I measured my across-the-chest resistance
as about 200 K ohms) in parallel to simulate me touching aerial and earth.
So there was a large internal resistance, but not large enough to prevent a
noticeable jolt.

After that I rigged up a wire from mains earth to the aerial amplifier's
screen connection, to make sure everything was earthed. All it needed was
one earthed appliance (the PC) and everything was OK, which is why I'd never
noticed the problem before, but as soon as that earthed connection was
removed, everything was "semi-live". Sod's Law: everything else was
double-insulated and so not earthed. Probably to avoid hum loops as much as
to avoid needing a three-pin mains lead.


I've only had a "proper" mains shock twice in my life. Once when I made the
elementary mistake of working on a tape recorder that was turned off (so
everything downstream of the mains switch was safe), forgetting that the
input terminals to the switch were live... This was in the old days of a
fuse box that only contained (wire) fuses, with no earth-leakage RCD. I
still have two marks on my finger where it touched the soldered switch pins
for the live and neutral feed: it looks like a snake bite ;-)


The second time was equally silly. I was changing a lot of GU10 light
fittings which had Philips Hue bulbs in them - the type of bulb is
important, because these can be turned off with the mains still live (there
is a switch inside the bulb which is controlled by a phone app). Each time I
did a few more fittings, I turned off the wall switch and also the circuit
breaker for the lighting circuit. Except for one set, when I made the stupid
mistake of thinking that the bulbs were not lit, therefore the power was off
at least at the wall switch. Wrong! On that occasion the house was protected
with an RCD, which did its job and tripped very quickly: I know that because
it also killed the table lamp that I was using for illumination while the
ceiling lights were supposedly off.

The second shock was much less sever that the first one, probably because of
the RCD, so I didn't have to pull my hand away.