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

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