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Re: exploding wire



Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>

Exploding wires make beautiful and varied pictures and are the most dramatic non Tesla photos around. Great for desktop wallpaper.
My gallery is here:
http://tesladownunder.com/Pulse_Power.htm

Peter

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

Here's a demo of exploding wires
http://web.mit.edu/Edgerton/www/ExplodingWire.html

They use 500 uF @ 800V to zap a shortish piece of NiCr wire. With their energies, I'm not sure they're really getting an honest explosion (as in creating a shock wave).

In my experience, it takes about a kJ to get a good explosion from a one meter long wire in the AWG 32 or finer area. Both aluminum and copper wire work. I ran 5-20 uF at 10+kV.

Exploding wires is a matter of peak powers, too.

There is a definite series of qualitatively obvious phenomena. From lowest to highest energy:
Melting
Melting into droplets with sparks  (a "pop", like a fuse burning out)
Melting and flashing over like a spark(a crackle or "flash", like any old spark, eg. from a TC)
Exploding (a distinct "bang" or "crack")

Visually, they're quite different. All of them, except the explosion, appear to "propagate" along the wire, at least in a meter long segment.

in order to explode, the wire has to liquefy, then vaporize, then ionize, before the material has a chance to move around. So, you have to put a fair amount of energy into the wire, fairly quickly. You can calculate the amount of energy required to vaporize the wire pretty easily by looking up the heat of fusion and vaporization for the material.

The dyanmics are quite interesting, because the resistance of the wire rises rapidly as it heats, so getting enough current into it quickly enough requires a substantial voltage.

Thanks for all you do,
Jim Mora