Sciencemadness Discussion Board

Electrostatic tidbits

Morgan - 24-9-2012 at 08:04

CHARGING MECHANISMS (page 45)

"Lower into an empty glass beaker two electrodes of differing materials (e.g. gold and magnesium) and connect an electro-meter across the two electrodes. When a suitable radio-active source (e.g. Po 210, 500 Cu) is placed at the bottom of the beaker, a potential of 1.2 volts will be registered between the electrodes, magnesium being negative with respect to gold. Remove the radioactive source and fill the beaker with sufficient water to partially immerse both electrodes. The electrometer will again register a potential of 1.2 volts and the same polarity."

"Both experiments deal with an electrochemical cell, using water for electrolyte in one case and air in the other. The fact that water contains ion pairs makes it an electrically conducting electrolyte which is vital for an electrochemical cell. In the first case, Fig. 22a, the beaker contains air instead of water, but the air is slightly ionized by the radioactive source, and although the number of ion pairs is relatively low, the ionized air is electrically conducting and exhibits the same properties characteristic of an electrolyte."

"At first it was disappointing to discover that the potentials in Table 1 were not at all proportional but rather inversely proportional to the work function potentials of the different materials in question. However, Table 1 has a very familiar appearance to the chemist; it resembles a chemical activity series in which the electrical potentials are values related to the oxidation energies of the materials in question. To further prove the electrochemical effect, the same materials were immersed in distilled water, two at a time. Differences of potential between the two materials were then measured and found to be directly proportional to the respective differences between their values in Table 1."

"From the experiments and the results of Table 1 it became clear that we were dealing with an electrochemical effect and the following conclusions were drawn: negative ions in air are formed from acidic molecules such as O2 and NO2. These molecules are electrophilic (electron seekers) and capture free electrons produced in air by the various ionization processes. The molecular ion, with its valence slightly reduced by a captured electron, still remains acidic and very active as an oxidizer. When the molecular ion with its piggyback electron oxidizes a surface material, negative charge is transferred by the captured electron to the surface. As more ions reach the surface, a negative back-emf will build up, eventually repelling any incoming ions until no more can reach the surface. Just as in the case of the drycell an electrical equilibrium potential is achieved."

(page 73)
"In the electrochemical charging mechanism convection currents simply bring natural ions of both signs in from outside and ventilate them through the drop population of the cloud. However, negative ions which are extremely reactive attach themselves to drop surfaces at the bottom of the cloud while the inert positive ions sieve through and are carried by the updrafts to the upper regions. The electrochemical charging mechanism, which is described in Chapter 3, is very effective and despite criticism by Vonnegut, Moore, Griffith and Willet (see section 2.7.3) is the only process which can easily be modelled in the laboratory."
"The diagram in Fig. 31 shows such a model constructed from two clumps of steel wool. The two sections of steel wool, one representing the bottom and the other the top of a thunder cloud, are electrically insulated from each other. A fan blows air through the cloud model to simulate the updraft winds inside a thunder cloud. A radioactive alpha particle source (Po 210, 500 micro Cu) near the fan feeds positive and negative ions at equal number into the cloud model. Negative ions are immediately captured by the electrochemical process in the bottom section while the inert positive ions pass through and reach the upper steel wool section where they stop together with the airflow. In a model the size of a large football over one hundred volts of charge separation is readily achieved. A small neon light, connected across the cloud model, demonstrates the lightning discharge in a realistic manner. The polonium 210 is readily available from several mail order suppliers and does not require a license."

http://www.scribd.com/doc/25953717/Atmospheric-Electrostatic...


[Edited on 24-9-2012 by Morgan]

Morgan - 24-9-2012 at 18:06

I don't think Accio's generator is going to be coming to a theater near you any time soon but it's interesting to think about. DARPA has given them a small amount of money.

"Each component is made up of recycled aluminum tubes and has no moving parts. Water is pumped in as wind blows through, forcing a mist of tiny water droplets out pinholes in the aluminum. The flow of water creates a charge, just as it does in thunderheads as water droplets rise and fall on wind currents."
http://www.crainsdetroit.com/article/20101114/FREE/311149953...
There's a graphic on this page.
http://theeestory.com/posts/185384

Here's a very simple Lord Kelvin water dropper demonstration from MIT. It would be fun to make something a little more sparky.
http://www.youtube.com/watch?v=-ahWs9YTJkc#t=3m36s

Some basic tips for making better sparks.

"For example, a flashlight might use 3 volts at 1 ampere, putting out three watts of visible and IR light. 3volts/1amp equals 3 ohms. So for a flashlight, any object with lots less than 3 ohms is a conductor, and any object with lots more than 3 ohms is an insulator. A flashlight "thinks" that a 1K resistor is a good insulator, while a 0.01 ohm wire is a good conductor."

"For electrostatics, the numbers are quite different. A Kelvin waterdrop generator might produce 20,000volts at 1/2 microamp. Dividing this voltage by this current gives 40,000,000,000 ohms. That's the line between insulator and conductor. Quite different than three ohms! So, if an object is to act as an insulator, its resistance must be MUCH greater than forty billion ohms! For a Kelvin generator, a ten-megohm piece of wood will act like a very good conductor. Is it any wonder that a bit of surface moisture can convert an insulating object into a conductor? The highest value of resistor commonly available in catalogs is 33 megohms, and most electrostatic devices will see this device not as a resistor, but as a dead short.
http://amasci.com/emotor/stathint.html

Morgan - 28-9-2012 at 11:40

"The picture was taken with a digital video camera under bright fluorescent light. The sparks are not quite as bright as they appear in the pictures, but they are nevertheless quite impressive to the uninitiated in electrostatics, not to mention being quite loud. These sparks are 5 1/2 inches (14cm) long, but under optimum conditions I have made sparks as long as seven inches (18cm). I think with a little tweaking of the configuration, they might be much longer."
http://www.coe.ufrj.br/~acmq/foster.html

Here's an example of the above and where I got the idea to try to make one myself. I set my leyden jar on a slab of copper and the solution is a mix of magnesium sulfate and salt. I tried CPVC and the gray PVC and both seem to work better than the plain white. The length of the PVC tube is 6 feet. Note how much crackle there is sliding the paper towel over the PVC. There was a cloth around the paper towel for insulation. With another design I was able to make a 13 inch spark.
http://www.youtube.com/watch?v=6w_18SqA6x8


Morgan - 30-9-2012 at 05:35

I thought it funny he drinks the water after the Kelvin water dropper experiment.
http://www.youtube.com/watch?v=2sSqzLPMb4s#t=5m19s

Sir William Thompson/Lord Kelvin and his water dropper. In one variation he uses copper filings.
http://books.google.com/books?id=2lgwAAAAIAAJ&pg=PA391&a...


[Edited on 30-9-2012 by Morgan]

Morgan - 1-10-2012 at 05:25

Static discharge
http://www.youtube.com/watch?v=JywjBAxxJHE

Morgan - 5-10-2012 at 12:19

An easier to read format and larger diagrams.
Proceedings of the Royal Society, June 20, 1867

"If a tube (fig. 3) be added to the lid to prevent currents of air from circulating into the interior of the jar, the insulation may be so good that the loss may be no more than one per cent. of the whole charge in three or four days. Two such jars may be kept permanently charged from year to year by very slow water-dropping arrangements, a drop from each nozzle once every two or three minutes being quite sufficient."
http://zapatopi.net/kelvin/papers/on_a_self-acting_apparatus...
http://zapatopi.net/kelvin/kidsclub/answer.html

[Edited on 5-10-2012 by Morgan]

Morgan - 1-2-2013 at 07:48

Can Ball Lightning Exist in a Vacuum?
http://www.readcube.com/articles/10.1038/245095a0

bfesser - 1-2-2013 at 08:01

Quote:
I have been within 50 cm of ball lightning in its smooth and unerring passage through an aircraft<sup>2,5</sup>. I carried a penknife in my trouser pocket, a steel tobacco tin in my left jacket pocket and a steel screwdriver in my right jacket pocket.

Wow. Doesn't that just date it. In the last paragraph of the article, the author proposes "ball lightning to exist in regions of very low pressure where it may not be recognized by the luminosity of the excited gas." I call bullshit. It wouldn't be proper lightning if it wasn't highly luminous. :P See: etymology of <a href="http://www.etymonline.com/index.php?term=lightning" target="_blank">'lightning'</a>.

[Edited on 2/1/13 by bfesser]

Morgan - 1-2-2013 at 13:37

"Over the years lightning was thought to be a predominantly low altitude (<10 km) phenomenon with little of its energy coupling to the mesosphere and ionosphere. As a result, recent observations relating lightning to energy dissipation at altitudes between 30 and 90 km came as a major surprise. These phenomena, grouped under the name of high altitude lightning (HAL), include (a) Red sprites, (b) Blue jets, (c) Gamma ray bursts, (d) Radio bursts (e) more? A diagram referring to the different phenomena and the location of their occurrence is shown in Fig 1.3."
http://fisica.ciencias.uchile.cl/alejo/thesis/node2.html#SEC...

"High speed photometer measurements show that the duration of sprites is only a few ms. Current evidence strongly suggests that sprites preferentially occur in decaying portions of thunderstorms and are correlated with large positive cloud-to-ground lightning strokes. The optical intensity of sprite clusters, estimated by comparison with tabulated stellar intensities, is comparable to a moderately bright auroral arc. The optical energy is roughly 10-50 kJ per event, with a corresponding optical power of 5-25 MW. Assuming that optical energy constitutes 1/1000 of the total for the event, the energy and power are on the order of 10-100 MJ and 5-50 GW, respectively."
"If sprites are only barely detectable by the unaided human eye, in intensified television images obtained from the ground and from aircraft they appear as dazzlingly complex structures that assume a variety of forms."
http://elf.gi.alaska.edu/#curres
https://www.google.com/search?q=high+altitude+lightning&...

[Edited on 1-2-2013 by Morgan]

Morgan - 15-3-2013 at 18:59

ELECTRO STATIC!
http://www.youtube.com/watch?v=7zp98GNsWIU#t=42s

Morgan - 15-1-2014 at 07:21

I thought this was a clever design.
Big sparks from a handheld electrophorus
http://www.youtube.com/watch?v=axgG_aSLKPM
http://www.rmax.com/wall-r-matte-plus3.asp

"One of the largest examples of an electrophorus was built in 1777 by German scientist Georg Christoph Lichtenberg.[7] It was 6 feet (2 m) in diameter, with the metal plate raised and lowered using a pulley system. It could reportedly produce 15 inch (38 cm) sparks."
http://en.wikipedia.org/wiki/Electrophorus

Morgan - 31-1-2014 at 13:19

Having experimented with PVC and PTFE as a source of static electricity, a great winter activity, I started to wonder if there were any somewhat common plastics containing iodine, just to see if that halogen had any beneficial or peculiar properties over the other halogenated plastics. I happened on these few tidbits involving iodine but couldn't find any basic studies on the electrostatic properties of iodine in plastics.

Photoconductivity in pure and iodine-doped thin polyvinylchloride films
http://iopscience.iop.org/0022-3727/13/2/004/pdf/jdv13i2pL39...

Photoconductivity
"Classic examples of photoconductive materials include the conductive polymer polyvinylcarbazole,[2] used extensively in photocopying (xerography); lead sulfide, used in infrared detection applications, such as the U.S. Sidewinder and Russian Atoll heat-seeking missiles; and selenium, employed in early television and xerography."
http://en.wikipedia.org/wiki/Photoconductivity

Someone doesn't like povidone-iodine
The mythology of povidone-iodine and the development of self-sterilizing plastics.
http://www.ncbi.nlm.nih.gov/pubmed/8421809

floggedaway - 19-2-2014 at 11:12

I have always considered a kelvin water dropper being a very elementary type of van de graf generator.

Morgan - 10-3-2022 at 08:10

Maybe not earthshaking but interesting ...
New droplet-based electricity generator: A drop of water generates 140V power, lighting up 100 LED bulbs
https://techxplore.com/news/2020-02-droplet-based-electricit...