Re: Exploding wire (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 22 Nov 2006 21:48:30 -0800
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>, hvlist <hvlist@xxxxxxxxxx>
Subject: Re: Exploding wire (fwd)

At 08:41 PM 11/22/2006, High Voltage list wrote:
>Original poster: Steven Roys <sroys@xxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Wed, 22 Nov 2006 11:17:35 -0800
>From: Peter Lawrence <Peter.Lawrence@xxxxxxx>
>To: High Voltage list <hvlist@xxxxxxxxxx>
>Subject: Re: Exploding wire (fwd)
>
>
>
>
> >>Hello All,
> >>
> >>
> >>
> >>I just bought 1400ft of .008, 32AWG piano wire. My Capacitor charge will be
> >>14.3uf @ 40KV, I could do up to 50KV but the history of the Geek 
> Mighty Caps
> >>is unknown. How many feet can I blow of this wire? Surely this 
> would be more
> >>spectacular then a copper wire. Am I in the right ballpark for gauge? I
> >>would like to reach 8 feet ~ 2.5 Meters. The caps are rated at near 9KJ at
> >>full charge.
> >
>
>hmmm, vaporized metal is vaporized metal, not sure why anyone would expect
>iron to be much different from anything else...


The kind of metal has a fairly significant effect.  It changes the 
resistance, so the trade between resistance and inductance is 
different. Ideally, you want the resistance to be such that the 
circuit is close to critically damped, so that all the energy is 
absorbed by the wire in that first quarter cycle, as opposed to over 
multiple cycles as the circuit rings down.  For a given 
configuration, there's not much you can do about inductance.

There's also a tradeoff in the amount of energy it takes to fuse and 
then vaporize the wire, which is different for different metals, not 
only because the melting and boiling points are different, but 
because the density of the materials are different.  The thermal 
capacities are similar for most metals.

but wait, there's more: the temperature coefficient of the resistance 
is also different for different metals.  As the wire gets hotter, its 
resistance increass, changing the circuit properties.


This is all very difficult to predict easily, hence the "try it and 
see if it works" advice.

Jim


>but then, I can't actually predict the outcome either, so let us know how
>it turns out !!!
>
>-Pete Lawrence.