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.
-- Tomi Engdahl
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a look at my electronics web links and documents at
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. The hand cranking probably would be the limitation on how much harm you could do to yourself.
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:
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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.
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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.
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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.
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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*!
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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.
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