@Don Alaska Almost. A modernized version of a Wimshurst static electric generator. Principle is thus: a large glass disc is spun by a hand-crank, "brushes" carrying away electrons which are "stored" in Capacitors called "Leyden Jars". Quite a high static charge can be achieved, enough to throw a pretty long spark. Those of us who have resided in quite cold climates, when humidity is low in Winter, will recall shuffling their feet over a carpet, and jumping when a spark is produced upon touching an object or person. Same principle. The Van deGraaff generator uses a moving endless belt having pulleys supporting it, like a vertical conveyor belt, to store static charge at it's top on a spherical metal surface. Much more to my liking is the Tesla Coil, of which I have built many. Tesla Coils operate differently from Static machines in that they are alternating current devices. Some incredibly pretty "fire" can be produced by them. A person hit by the "flame" experiences no shock, yet the Corona Discharge as it is correctly called, can easily ignite a scrap of paper through which it passes. Various "tricks" may be performed, such as the holding of a Fluorescent lamp in one's hand, which illuminates mysteriously without any wires as the Coil is approached. Frank
Very interesting @Don Alaska and @Frank Sanoica. Out of curiosity I had to google Wimshurst static electric generator to find its purpose.
Frank and Don, you are both knowledgeable in the operation of these machines, which I admire! The one in the picture, which I designed and built, is a Bonetti Machine, and uses TWO 36" acrylic discs which are counter-rotating on a common shaft. Both the Wimshurst and the Bonetti machines were developed in the 1870's in Europe. Unlike the Wimshurst, which also uses 2 counter-rotating discs, the Bonetti uses no conductive foils and brushes to pick up the electrostatic charge, but uses metal combs which do not touch the discs. The charge is transferred by induction, and is stored in the 2 Leyden Jar capacitors until the voltage is high enough to break down the gap between the 2 copper spheres. I calculate that I'm generating over 250,000 volts with the gap as shown. The Wimshurst is self-generating, but my Bonetti has to be "primed" with the small Van de Graaff shown to get it producing! I also built a Van de Graaff with a 30" discharge sphere, but no longer use it, as the long arcs interfered with the household wiring, and kept tripping breakers, so I dismantled it and use the sphere as a garden ornament! It generated over 1 million volt discharges which were 4 to 5 feet long. Hal
@Hal Pollner Fantastic! How you have whetted my appetite for H.V. apparatus, something I have needed, being away from such activity since I taught High School Math in '02-'03 in Missouri. I gave the Seniors the opportunity to earn extra credit by building a Tesla Coil, under my direction. Sadly, I have no pictures of it, but a short description is in order. One girl supplied the Primary Coil form, a porcelain flower pot about 14 inches in diameter. The Secondary was wound on some plastic tubing about 3" in diameter, of AWG 24 speaker wire. I mounted it on rollered supports, and those kids hand-wound a perfect coil about 4 feet long! Primary power was supplied by one of my old neon sign transformers, 15,000 volts. I wound two short #10 choke coils, placed them in series with the transformer secondary, to protect it. Spark gap was enclosed within a teflon cylinder I turned on my lathe, ends having threaded electrodes for adjustability. Capacitors. 20 or so green glass beer bottles! They jokingly said that beer was the REAL reason for my proposal, as I had to empty the bottles! Those stood, filled with salt water, in a plastic dish tub, also full of salt water. 3/16-inch copper rods, nutted to bottle caps, reached down into the liquid in the bottles. Tuning was achieved by switching in bottles using clipped connecting leads. Streamers produced were on the order of a foot long or more. Fluorescent ceiling lights close to the coil in operation flickered ominously. Hand-held 4-foot tube illuminated at near-normal intensity. The school staff was as freaked out by this as were the students who built it! I long to build another. Perhaps I will! Frank
Frank, after building my last Tesla Coil about 15 years ago, I realized that the primary voltage was dangerous, as the transformer produced 15,000 volts at a lethal current of 50 milliamps, which could kill me if the 15KV 60Hz current contacted my body! No more Tesla Coils! The spectacular secondary discharge was harmless, as it was at a high RF frequency, which flows over the skin, rather than penetrating the body. Here's a shot of my Wimshurst Machine, which produces a mild discharge of 75,000 volts at just a few microamps! (Note the 2 small balls behind the discs where the arc is formed.) Hal
Hal @Hal Pollner Beautiful machine you built there! Just yesterday, doing some snooping about Tesla Coils, I learned something most interesting, as well as disappointing. It had been stated since Day 1 that "skin-effect", the fact that high-voltage high-frequency charge exists only on the surface of a conducting body, thus explaining the fact that one feels no "shock". It's not true! While "current density" is highest on the surface, and decreases towards the center of the conductor, where it is zero, it has been determined that the real reason we don't feel it is that our nerve endings just aren't sensitive to A.C. exceeding about 20khz. "The high voltage radio frequency (RF) discharges from the output terminal of a Tesla coil pose a unique hazard not found in other high voltage equipment: when passed through the body they often do not cause the painful sensation and muscle contraction of electric shock, as lower frequency AC or DC currents do.[58][17][59][60] The nervous system is insensitive to currents with frequencies over 10 – 20 kHz". "If the arcs from the high voltage terminal strike the bare skin, they can cause deep-seated burns called RF burns.[64][65] This is often avoided by allowing the arcs to strike a piece of metal held in the hand, or a thimble on a finger, instead. The current passes from the metal into the person's hand through a wide enough surface area to avoid causing burns.[17] Often no sensation is felt, or just a warmth or tingling." "However this does not mean the current is harmless.[66] Even a small Tesla coil produces many times the electrical energy necessary to stop the heart, if the frequency happens to be low enough to cause ventricular fibrillation." "An erroneous explanation for the absence of electric shock that has persisted among Tesla coil hobbyists is that the high frequency currents travel through the body close to the surface, and thus do not penetrate to vital organs or nerves, due to an electromagnetic phenomenon called skin effect.[67][17][70][71] This theory is false.[72][73][74][58][68][75] RF current does tend to flow on the surface of conductors, but the depth to which it penetrates, called skin depth, depends on the resistivity and permittivity of the material as well as the frequency.[76][77] Although skin effect limits currents of Tesla coil frequencies to the outer fraction of a millimeter in metal conductors, the skin depth of the current in body tissue is much deeper due to its higher resistivity and lower permittivity. The depth of penetration of currents of Tesla frequency (0.1 - 1 MHz) in human tissues is roughly 24 to 72 cm (9 to 28 inches).[77][76][58] Thus skin effect has little influence on the path of the current through the body;[75] it takes the path of lowest electrical impedance to ground, and can easily pass through the core of the body.[78][58][77] In the medical therapy called longwave diathermy, RF current of Tesla frequencies was used for decades for deep tissue warming, including heating internal organs such as the lungs.[78][59] Modern shortwave diathermy machines use a higher frequency of 27 MHz, which would have a correspondingly smaller skin depth, yet these frequencies are still able to penetrate deep body tissues.[73]." See: https://en.wikipedia.org/wiki/Tesla_coil#Health_hazards So, I live (very fortunate, considering a life-long exposure to the hazards of electrocution), and learn! Frank
Frank, I will concede that you are the Authority in explaining the effects of different kinds of Electric Currents and their effects on the human body. (This photo shows the setup in my home lab for calibrating the Right Ascension drive in tracking telescopes.The earth turns on its axis at the rate of one revolution in 24 hours, or 15 degrees per hour, or 1/4 degree per minute. (15 seconds of arc) If the scope's tracking rate is not true, the image will drift in the eyepiece.) Hal
@Hal Pollner Please, I am Authority only in getting myself in trouble......... Very nice set-up in your picture! Know very little about Astronomy, and wonder a lot about "geo-synchronous" orbitting satellites. Like, how often must corrections be made, so that the poor darlings watching those horrible TV drug commercials don't lose their signals? About getting myself in trouble: in the fifth grade, the teacher insisted the Moon does not rotate in any way. Then, the textbook claimed the moon shows it's same "face" to Earth all the time. I insisted that as the Moon moved about the Earth, from one location to half-way around the Earth, it had to have rotated half-way about it's axis. Teacher was fuming! Another time, much later, at DeVry Technical Institute, studying Differential Calkculus, the text author claimed pistons in an internal combustion engine move in Simple Harmonic Motion. I never thought about this very much, but one guy, a bit older than I, interrupted by stating they most certainly do NOT. Taken aback, the Instructor asked for time to study the argument. My classmate had learned of the importance of Connecting Rod length vs. crankshaft stroke in the Army. Next day, teach. conceded the book was wrong, and explained why. Pistons actually move up and down such that the "Sine Wave" described is modified, having unequal areas under the curve. Frank