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Devise to shock earth worm

J

John

Jan 1, 1970
0
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
 
T

Tomi Holger Engdahl

Jan 1, 1970
0
John said:
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?

I have read that worms do not like some electricity going through them.
Some electricity going through them will cause that they go to surface.

When a metal rod with some voltage (different than
the overal ground potential is) is pushed to ground, it will
cause a local voltage potential very near to rod rise to the
voltager applied to rod. When going more distance away from rod,
the potential will drop down to the actual ground potential
some meters away from rod. This potential difference is caused by
ground resistance and the current flowing on ground (starting
from the rod). When worms are in ground where the current flows,
some part of current flows through them.

This device did not blow the fuse because either the grounding
resistance of the this rod was high enough that the current
flowing through it will not blow fuse (for example 20 ohms
gournding resistance causes 6A current for 120V AC and
will not blow 15A fuze, if grounding resistance is 4 ohms then
current will be 30 amperes that will blow 15A fuse within some minutes)
or the system in use had some built in current limiting device
that makes sure that current is within limits allowed by fuses.


This kind of device sounds to me like a very dangerous equipment
that would be quite impossible to fullfill the modern electrical
safety regulations.
 
T

Tomi Holger Engdahl

Jan 1, 1970
0
Salmon Egg said:
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.
 
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