Newsgroups: alt.engineering.electrical
Subject: Re: Devise to shock earth worm
References: <[email protected]> 
Salmon Egg  writes:

> On 11/21/07 5:29 PM, in article [email protected],
> "John"  wrote:
> 
> > I had an uncle who used a electric devise to get worms from the lawn for use
> > as fish bait.  This devise had a pointed  ~ 1/4" metal rod protected by a
> > spring loaded plastic sleeve which was inserted into the ground.  Apparently
> > the sleeve was intended to prevent shocking the user.  Then the plug was
> > connected to the an electric outlet.  The worms in the an area of several
> > sq. ft would come to the surface and be caught.  This devise worked better
> > when the ground was wet or at least damp.  How did it work and why didn't it
> > blow a fuse?
> > 
> > Thanks for comments
> > 
> > John 
> > 
> > 
> I believe the original version of such a device depended upon a hand cranked
> telephone ringer magneto. IIRC, Edmund Scientific sold these for that
> purpose when these ringers went out of use.
> 
> If you ever got across such a device, it was very uncomfortable. Telephone
> ringing frequencies are probably more dangerous than 60Hz. 

To my knowledge telephone ringing frequencies are less dangerous 
for humans than 50 Hz or 60 Hz electrical power. 
The telephone line frequencies are lower (20-25 Hz quite often). 
They can be painful, activate musches heavily, but with then 
is it much less propably that you "stick" to the power source 
(getting constant power going through you) and is less propable 
that they disturb your heart operation in bad way 
(ventricular fibrillation, cardiac arrest etc.). 
   
From: http://en.wikipedia.org/wiki/Electric_shock
The perception of electric shock can be different depending on the
voltage, duration, current, path taken, frequency, etc. Current
entering the hand has a threshold of perception of about 5 to 10 mA
(milliampere) for DC and about 1 to 10 mA for AC at 60 Hz. Shock
perception declines with increasing frequency, ultimately disappearing
at frequencies above 15-20 kHz.


From: http://www.pat-testing.info/electric-shock.htm
A low-voltage (110 to 220 V), 60-Hz AC current traveling through the
chest for a fraction of a second may induce ventricular fibrillation
at currents as low as 60mA. With DC, 300 to 500 mA is required. If the
current has a direct pathway to the heart (eg, via a cardiac catheter
or other electrodes), a much lower current of less than 1 mA, (AC or
DC) can cause fibrillation. Fibrillations are usually lethal because
all the heart muscle cells move independently. Above 200mA, muscle
contractions are so strong that the heart muscles cannot move at all.

DC tends to cause continuous muscular contractions that make the
victim hold on to a live conductor, thereby increasing the risk of
deep tissue burns. On the other hand, mains-frequency AC tends to
interfere more with the heart's electrical pacemaker, leading to an
increased risk of fibrillation. AC at higher frequencies holds a
different mixture of hazards, such as RF burns and the possibility of
tissue damage with no immediate sensation of pain. Generally, higher
frequency AC current tends to run along the skin rather than
penetrating and touching vital organs such as the heart.


From: http://pchem.scs.uiuc.edu/pchemlab/electric.htm
The frequency of the AC has lots to do with the effect on the human
body. Unfortunately, 60 cycles is in the most harmful range. At the
house voltage frequency, as little as 25 volts can kill. On the other
hand, people have withstood 40,000 volts at a frequency of a million
cycles or so without fatal effects.
A very little current can produce a lethal electric shock. Any current
over 10 ma. will result in serious shock.



From: http://yarchive.net/phone/20hz.html
Normal ringing voltage is about 100 volts at 20 Hz, and it is truely
nasty stuff.  Getting jerked around by 20 Hz current will teach some
true respect.  Don't confuse that with a relatively mild 60 Hz shock.
(Either one can kill you.) 
But, the ring voltage is current limited. 
And I'll admit to being semi
scared to death of 60 Hz house current, but I'm also ten times as
scared of 20 Hz ring current.  It *HURTS*!

From: http://www.naturalhandyman.com/iip/inftelephone/inftel3.html
However, when the phone rings, a series of high voltage AC surges come
through the lines, up to 100 volts, and this can be dangerous,
especially to people with health conditions, pacemakers, etc. 



> The hand cranking
> probably would be the limitation on how much harm you could do to yourself.

Yes it will limit that quite much. 

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/