Lichtenberg figure

By then pressing blank sheets of paper onto these patterns, Lichtenberg was able to transfer and record these images, thereby discovering the basic principle of modern xerography.

Two-dimensional (2D) Lichtenberg figures can be produced by placing a sharp-pointed needle perpendicular to the surface of a non-conducting plate, such as of resin, ebonite, or glass.

A source of high voltage such as a Leyden jar (a type of capacitor) or a static electricity generator is applied to the needle, typically through a spark gap.

[citation needed] In addition to the distribution of colors thereby produced, there is also a marked difference in the form of the figure, according to the polarity of the electrical charge that was applied to the plate.

If the charge areas were positive, a widely extending patch is seen on the plate, consisting of a dense nucleus from which branches radiate in all directions.

Heinrich Rudolf Hertz employed Lichtenberg dust figures in his seminal work proving Maxwell's electromagnetic wave theories.

Peter T. Riess (a 19th-century researcher) theorized that the negative electrification of the plate was caused by the friction of the water vapour, etc., driven along the surface by the explosion that accompanies the disruptive discharge at the point.

When a high voltage is applied across the surface, leakage currents may cause localized heating and progressive degradation and charring of the underlying material.

First published by Duke professor Adrian Bejan in 1996, the constructal law is a first principle of physics that summarizes the tendency in nature to generate configurations (patterns, designs) that facilitate the free movement of the imposed currents that flow through it.

The constructal law predicts that the tree-like designs described in this article should emerge and evolve to facilitate the movement (point-to-area) of the electrical currents flowing through them.

[12] Branching root-shaped "fulgurite" mineral deposits may also be created as sand and soil are fused into glassy tubes by the intense heat of the current.

From the direction and shape of the trees and their branches, an experienced high-voltage engineer can see exactly the point where the insulation began to break down, and using that knowledge, possibly find the initial cause as well.

Electrons emerging from the accelerator have energies up to 25 MeV and are moving at an appreciable fraction (95 – 99+ percent) of the speed of light (relativistic velocities).

Since acrylic is an excellent electrical insulator, these electrons become temporarily trapped within the specimen, forming a plane of excess negative charge.

Under continued irradiation, the amount of trapped charge builds until the effective voltage inside the specimen reaches millions of volts.

During breakdown, branching tree or fern-like conductive channels rapidly form and propagate through the plastic, allowing the trapped charge to suddenly rush out in a miniature lightning-like flash and bang.

During the discharge, the powerful electric sparks leave thousands of branching chains of fractures behind, creating a permanent Lichtenberg figure inside the specimen.