Subject: [stella] Jacobs ladder (off topic) From: Chris Wilkson <ecwilkso@xxxxxxx> Date: Mon, 3 Dec 2001 13:01:22 -0500 (EST) |
On Mon, 3 Dec 2001, John Saeger wrote: > BTW, I had a question about your Jacobs Ladder. ;-) Do you think a > transformer from an old Microwave oven would work for something like this? > I think they *only* put out around a KV or so, but they've got lots of > current. Hi John, If you want to build a Jacobs Ladder, you want a high voltage. The current doesn't really matter (see below). The power supply voltage has to be able to overcome the dielectric (air) resistance to form a spark/arc. Once the arc is formed, it's essentially a zero resistance path. The arc rises due to the heated air/plasma rising. So if you want it to rise faster, dump more power into the arc. In this case, the distance between the electrodes sets the minimum voltage required, so the current will set the power. Also, most jacobs ladders are only a few feet long. And the gap increases as you go up. So eventually there isn't enough voltage to maintain the arc. It breaks and starts over at the bottom - the narrowest point in the spark channel. If you make the 2 rods parallel (with balls or whatever at the bottom to start the arc), the arc will still rise to the end of the rods, no matter how long they are, but it won't break right at the end. Instead you'll get a really cool, scary, ribbony arc whose ends are still tied to the rods, but whose center rises due to the heated air currents. An arc riding on an eddy is really awe inspiring! The one we have at work uses an old oil burner transformer. I know it puts out 30mA, quasi-regulated, but I forget the voltage. It's either 3kV or 30 kV. 3kV seems right....but that might be under load.... Hmm...speaking of load, that's another contributing factor. As the arc gets shorter (with constant current) the voltage goes down...V=IR. So a larger current capacity actually will help you get longer arcs. That isn't very clear, but I have to go...sorry. :) -Chris ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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