High Voltage Forum

High voltage => Static electricity => Topic started by: haversin on October 25, 2019, 03:16:12 AM

Title: Lichtenberg figures
Post by: haversin on October 25, 2019, 03:16:12 AM
Some initial results are shown here:

https://photos.app.goo.gl/GuKVSEsAgJjQq1Nk7 (https://photos.app.goo.gl/GuKVSEsAgJjQq1Nk7)
click on the google photo image when it comes up for a larger version.

  The top two figures that look like fireworks are from positive discharges and the bottom five are from negative discharges. An aluminum cigar tube was placed open end down on the plastic and a charged pie tin was brought near the cigar tube until a spark discharge occurred. The cigar tube was then removed and the plastic was dusted with baking power. The pie tin had an insulating handle and was charged with a Van de Graaff generator.

  I'm now charging a 2 nF salt water cap and discharging it through the same cigar tube placed on 2 mm thick acrylic sheet. I started grounding the cigar tube before I  pick it up and discovered that this grounding was causing a smaller second discharge of opposite polarity to the first.
 These next two photos are with out grounding the cigar tube before removal. Positive on the left and negative on the right.

https://photos.app.goo.gl/ooJa3hBvpdrTjsh19 (https://photos.app.goo.gl/ooJa3hBvpdrTjsh19)
https://photos.app.goo.gl/eET8rr1S2dCK8fmQA (https://photos.app.goo.gl/eET8rr1S2dCK8fmQA)

This photo is with grounding the cigar tube before removal.

https://photos.app.goo.gl/5MpABG1qwAz7DJTh9 (https://photos.app.goo.gl/5MpABG1qwAz7DJTh9)


The small inner ring of the positive discharge is the second negative discharge.
The negative discharge on the right, has an inner positive discharge that is almost as large as it is. This is because positive figures are much larger than negative for the same voltage.
Title: Re: Lichtenberg figures
Post by: Mads Barnkob on November 05, 2019, 08:02:46 PM
It seems you are getting the largest and most branching from static electricity and positive discharges. The salt water capacitor properly has a discharge current much higher, so voltage drops faster and it can not reach just as far.

Do you have any bigger discharge capacitors?

Have you had success with making such Lichtenberg figures into a piece of plywood from a capacitor discharge?

Thanks for sharing :)
Title: Re: Lichtenberg figures
Post by: haversin on November 06, 2019, 02:34:51 AM
It seems you are getting the largest and most branching from static electricity and positive discharges. The salt water capacitor properly has a discharge current much higher, so voltage drops faster and it can not reach just as far.

According to the literature, the size of both positive and negative figures is a linear function of the voltage assuming the same setup. The size of the initial positive figures using a charged pie tin (first photo in initial post) were about 9 cm in diameter and only the tips of the branches were distinct. The size of the positive figures using the 2 nF cap (shown in the rest of the photos of the initial post) varied from about 8 to 10 cm in diameter due to different charge voltages on the 2 nF salt water cap. I did a rough count of about 8 seconds charging time using the VDG.

  The following two photos show positive figures over 10 cm in diameter using the 2 nF cap on a 11 x 15.5 cm acrylic block 24 mm thick. The count was about 12 seconds charging time. Assuming the VDG is a constant current source of 4.5 uA (which is only approximate because of leakage at these high voltages) the voltage is about 27 kV.

https://photos.app.goo.gl/A8XefrTsjtURstbh6 (https://photos.app.goo.gl/A8XefrTsjtURstbh6)
https://photos.app.goo.gl/WQLipRSz6KdHtPVC7 (https://photos.app.goo.gl/WQLipRSz6KdHtPVC7)

Do you have any bigger discharge capacitors?

No, but the 2 nF cap is only partially discharging. My main focus right now is to show the charge polarity map using two different powders.

Have you had success with making such Lichtenberg figures into a piece of plywood from a capacitor discharge?


I have not tried. The videos I've seen of the wood burning Lichtenberg figures use wet wood and neon sign transformers. The physics of the wood burning does not interest me as much as the dust figures which show such amazing patterns.

Thanks for sharing :)

Thanks for running this forum!

For a grand finale.

This is one of the more “artsy” figures. Positive discharge thru 48 mm diameter metal sphere resting on 2 mm thick acrylic with grounded back plane. After discharge the sphere was accidentally grounded and rolled a little toward the upper left.  Blobs of negative discharge can be seen as the sphere rolled.
click on image for larger view.

https://photos.app.goo.gl/qYZXZoethD3YFVBCA (https://photos.app.goo.gl/qYZXZoethD3YFVBCA)