Re: Jurassic Park

[dg04@ns1.cc.lehigh.edu (DAVID GRUMBINE)]

>But you are wrong about the electric fence having almost no resistance!

No, the fence would have low resistance.  Maybe a good sice impedance, but...

>The current does not flow along the fence! The voltage is applied to the
>fence and flows to ground when something closes the path. The reason
>pulsing the high voltage saves money is that the wooden posts are
>not perfect insulators so there would be some leakage current.

That just means I wasn't quite familiar with the setup of these fences.  Where
the voltage is applied wouldn't affect the resistance!  But I stand corrected
as to where the current flows to.  (I know, never use a preposition to end
a sentence with.  :-)

[ about real high voltages and wooden insulators... ]

>Hmmm... True again. But I was only speaking of the cattle fences I saw.
>A dry stick would have about the same resistance as the fence posts (there
>were no insulators between the wires and the posts). And the voltage was
>considerably less than 10kV. Dry wood isn't a bad insulator (it was used
>in early automobile ignition systems!) If a dry stick would get zapped
>by the cattle fence then the fence's own posts would be getting
>continually zapped, too (whatever the technical definition of
>'zapped' is!!!)

Ok, yes in a cattle fence this is true, but the fences in the movie had BIG
glass insulators and other neat stuff like that, so the leakage should be
MUCH less than if a wooden one was used, and also the risk of a fire!

[ pulses making a small spark... ]

>Me too! But I neglected to mention that these were very short duration
>pulses occuring about once every second or two...

Yeah, that low frequency of pule rate would make a small spark.  Unless you
blew out something else.....

[ suspending beliefe..]
>No kidding! I just abo
ut crapped myself when the T-Rex was
>chasing them in the jeep!  :-)

Guy sitting next to me almost lost it then the Velociraptor decided that
now that power was restored it could eat Dr. Sattler (sp? been a while
since i read the book.) never mind the steel wall between it and her.

-- 

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The oppinions expressed above may or may not be my own.  But I'm not telling.

Physics is fun! ....  Honest.
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Dave Grumbine, Jr.       dg04@Lehigh.EDU