Hi Alex



At 12:28 98.03.06 -0800, you wrote:
>richard skinner wrote:
>>
>> No, I haven't but, I ran across something very interesting, at least to me,
>> but I am Ignorant to allot
>> of things in this world.
>>
>> A SUPER CAP.   I watched a guy last week charge a roll of clx wire on a
>> spool, then shoot sparks
>> from the ends when he shorted the wire at the end.  I never much thought
>> about a large spool
>> of wire acting as a capacitor, but all the ingredients are there.  He was
>> telling me that you should
>> always short the wires on a spool before working with it as it can store
>> static electricity and it can get
>> rather high over time, if the conditions are correct.  Hum, that ought
to run
>> a clock for sometime?
>
>???? Capacitance in a coil? The basic ingredients of a capacitor are two
>conductors seperated by an insulator ---||---
>A coil of wire on the other hand is just one long conductor. It may have
>a lot of inductance, but I can't see it having much capacitance (or are
>you talking about a two cored cable? Even then there would only be a
>small amount between the cores).
>
>--
>------------------- Linux- the choice of a GNU generation.
>--------------------
>: Alex Holden- Caver, Programmer, Land Rover nut, and Radio amateur (M1
>CJD). :
>-------------- http://www.geocities.com/CapeCanaveral/Lab/1532/
>---------------
>

When you test the insulation of a long spool of cable (one end connected to
a power source and the other open), when you disconect it from the power
source and leave it open the transient efect can creat a surge at one end
of the cable (the one connected with the power source). As the cable is
open at both ends this surge travels from one end to the other (as a
reflectd wave) until all its energy is exausted by the cable losses. If you
have a good quality cable this energy can stay there for quite a while.
If we are talking about high voltage cables (energy transportation lines),
this efect can kill pepople toutching the cable days after it has been tested.
The only safe way to avoid this is to conect the cable to a correctly
adapted load until all residual energy gets exausted before stocking the
cable.

        Jorge F

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cumprimentos / best regards
      Jorge Ferreira          mailto://jorgegf@mail.telepac.pt
------ Make sure brain is in gear before engaging mouth -------
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