Static electricity often just seems like an everyday annoyance when a wool sweater crackles as you pull it off, or when a doorknob delivers an unexpected zap. Regardless, the phenomenon is much more fascinating and complex than these simple examples suggest. In fact, static electricity is direct observable evidence of the actions of subatomic particles and the charges they carry.
While zaps from a fuzzy carpet or playground slide are funny, humanity has learned how to harness this naturally occurring force in far more deliberate and intriguing ways. In this article, we’ll dive into some of the most iconic machines that generate static electricity and explore how they work.
What Is It?
Before we look at the fancy science gear, we should actually define what we’re talking about here. In simple terms, static electricity is the result of an imbalance of electric charges within or on the surface of a material. While positively-charged protons tend to stay put, electrons, with their negative charges, can move between materials when they come into contact or rub against one another. When one material gains electrons and becomes negatively charged, and another loses electrons and becomes positively charged, a static electric field is created. The most visible result of this is when those charges are released—often in the form of a sudden spark.
Since it forms so easily on common materials, humans have been aware of static electricity for quite some time. One of the earliest recorded studies of the phenomenon came from the ancient Greeks. Around 1000 BC, they noticed that rubbing amber with fur would then allow it to attract small objects like feathers. Little came of this discovery, which was ascribed as a curious property of amber itself. Fast forward to the 17th century, though, and scientists were creating the first machines designed to intentionally store or generate static electricity. These devices helped shape our understanding of electricity and paved the way for the advanced electrical technologies we use today. Let’s explore a few key examples of these machines, each of which demonstrates a different approach to building and manipulating static charge.
The Leyden Jar
Though not exactly a machine for generating static electricity, the Leyden jar is a critical part of early electrostatic experiments. Effectively a static electricity storage device, it was independently discovered twice, first by a German named Ewald Georg von Kleist in 1745. However, it gained its common name when it was discovered by Pieter van Musschenbroek, a Dutch physicist, sometime between 1745 and 1746. The earliest versions were very simple, consisting of water in a glass jar that was charged with static electricity conducted to it via a metal rod. The experimenter’s hand holding the jar served as one plate of what was a rudimentary capacitor, the water being the other. The Leyden jar thus stored static electricity in the water and the experimenter’s hand.
Eventually the common design became a glass jar with layers of metal foil both inside and outside, separated by the glass. Early experimenters would charge the jar using electrostatic generators, and then discharge it with a dramatic spark.
The Leyden jar is one of the first devices that allowed humans to store and release static electricity on command. It demonstrated that static charge could be accumulated and held for later use, which was a critical step in understanding the principles that would lead to modern capacitors. The Leyden jar can still be used in demonstrations of electrostatic phenomena and continues to serve as a fascinating link to the history of electrical science.
The Van de Graaff Generator
Perhaps the most iconic machine associated with generating static electricity is the Van de Graaff generator. Developed in the 1920s by American physicist Robert J. Van de Graaff, this machine became a staple of science classrooms and physics demonstrations worldwide. The device is instantly recognizable thanks to its large, polished metal sphere that often causes hair to stand on end when a person touches it.
The Van de Graaff generator works by transferring electrons through mechanical movement. It uses a motor-driven belt made of insulating material, like rubber or nylon, which runs between two rollers. At the bottom roller, plastic in this example, a comb or brush (called the lower electrode) is placed very close to the belt. As the belt moves, electrons are transferred from the lower roller onto the belt due to friction in what is known as the triboelectric effect. This leaves the lower roller positively charged and the belt carrying excess electrons, giving it a negative charge. The electric field surrounding the positively charged roller tends to ionize the surrounding air and attracts more negative charges from the lower electrode.
As the belt moves upward, it carries these electrons to the top of the generator, where another comb or brush (the upper electrode) is positioned near the large metal sphere. The upper roller is usually metal in these cases, which stays neutral rather than becoming intensely charged like the bottom roller. The upper electrode pulls the electrons off the belt, and they are transferred to the surface of the metal sphere. Because the metal sphere is insulated and not connected to anything that can allow the electrons to escape, the negative charge on the sphere keeps building up to very high voltages, often in the range of hundreds of thousands of volts. Alternatively, the whole thing can be reversed in polarity by changing the belt or roller materials, or by using a high voltage power supply to charge the belt instead of the triboelectric effect.
The result is a machine capable of producing massive static charges and dramatic sparks. In addition to its use as a demonstration tool, Van de Graaff generators have applications in particle physics. Since they can generate incredibly high voltages, they were once used to accelerate particles to high speeds for physics experiments. These days, though, our particle accelerators are altogether more complex.
The Whimsical Wimshurst Machine
Another fascinating machine for generating static electricity is the Wimshurst machine, invented in the late 19th century by British engineer James Wimshurst. While less famous than the Van de Graaff generator, the Wimshurst machine is equally impressive in its operation and design.
The key functional parts of the machine are the two large, circular disks made of insulating material—originally glass, but plastic works too. These disks are mounted on a shared axle, but they rotate in opposite directions when the hand crank is turned. The surfaces of the disks have small metal sectors—typically aluminum or brass—which play a key role in generating static charge. As the disks rotate, brushes made of fine metal wire or other conductive material lightly touch their surfaces near the outer edges. These brushes don’t generate the initial charge but help to collect and amplify it once it is present.
The key to the Wimshurst machine’s operation lies in a process called electrostatic induction, which is essentially the influence that a charged object can exert on nearby objects, even without touching them. At any given moment, one small area of the rotating disk may randomly pick up a small amount of charge from the surrounding air or by friction. This tiny initial charge is enough to start the process. As this charged area on the disk moves past the metal brushes, it induces an opposite charge in the metal sectors on the other disk, which is rotating in the opposite direction.
For example, if a positively charged area on one disk passes by a brush, it will induce a negative charge on the metal sectors of the opposite disk at the same position. These newly induced charges are then collected by a pair of metal combs located above and below the disks. The combs are typically connected to Leyden jars to store the charge, until the voltage builds up high enough to jump a spark over a gap between two terminals.
The Wimshurst machine doesn’t create static electricity out of nothing; rather, it amplifies small random charges through the process of electrostatic induction as the disks rotate. As the charge is collected by brushes and combs, it builds up on the machine’s terminals, resulting in a high-voltage output that can produce dramatic sparks. This self-amplifying loop is what makes the Wimshurst machine so effective at generating static electricity.
The Wimshurst machine is seen largely as a curio today, but it did have genuine scientific applications back in the day. Beyond simply using it to investigate static electricity, its output could be discharged into Crookes tubes to create X-rays in a very rudimentary way.
The Electrophorus: Simple Yet Ingenious
One of the simplest machines for working with static electricity is the electrophorus, a device that dates back to 1762. Invented by Swedish scientist Johan Carl Wilcke, the electrophorus consists of two key parts: a flat dielectric plate and a metal disk with an insulating handle. The dielectric plate was originally made of resinous material, but plastic works too. Meanwhile, the metal disk is naturally conductive.
To generate static electricity with the electrophorus, the dielectric plate is first rubbed with a cloth to create a static charge through friction. This is another example of the triboelectric effect, as also used in the Van de Graaff generator. Once the plate is charged, the metal disk is placed on top of it. The disc then becomes charged by induction. It’s much the same principle as the Wimshurst machine, with the electrostatic field of the dielectric plate pushing around the charges in the metal plate until it too has a distinct charge.
For example, if the dielectric plate has been given a negative charge by rubbing, it will repel negative charges in the metal plate to the opposite side, giving the near surface a positive charge, and the opposite surface a negative charge. The net charge, though, remains neutral. But, if the metal disk is then grounded—for example, by briefly touching it with a finger—the negative charge on the disk can drained away, leaving it positively charged as a whole. This process does not deplete the charge on the dielectric, so it can be used to charge the metal disk multiple times, though the dielectric’s charge will slowly leak away in time.
Though it’s simple in design, the electrophorus remains a remarkable demonstration of static electricity generation and was widely used in early electrostatic experiments. A particularly well-known example is that of Georg Lichtenberg. He used a version a full two meters in diameter to create large discharges for his famous Lichtenberg figures. Overall, it’s an excellent tool for teaching the basic principles of electrostatics and charge separation—particularly given how simple it is in construction compared to some of the above machines.
Zap
Static electricity, once a mysterious and elusive force, has long since been tamed and turned into a valuable tool for scientific inquiry and education. Humans have developed numerous machines to generate, manipulate, and study static electricity—these are just some of the stars of the field. Each of these devices played an important role in furthering humanity’s understanding of electrostatics, and to a degree, physics in general.
Today, these machines continue to serve as educational tools and historical curiosities, offering a glimpse into the early days of electrical science—and they still spark fascination on the regular, quite literally. Static electricity may be an everyday phenomenon, but the machines that harness its power are still captivating today. Just go to any local science museum for the proof!
Don’t forget the Pelletron !
There is also the https://en.wikipedia.org/wiki/Kelvin_water_dropper generator.
I remember building Van de Graff generators with my grandfather. The most horrific part was the sound of the jigsaw cutting the steel globe (that is the spherical model of the earth) and the smell of the paint stripper, slowly dissolving the continents. We of course would only built in the winter, as it was too humid for them to work properly during the rest of the year. They worked the fairly well. Grandpa used to think it was funny to let the sparks jump to his forearm, until one evening he inspected the damage and found his skin covered in what looked like dozens of mild mosquito bites. According to the old man, it wasn’t uncomfortable, but it was clear enough that being a human discharge terminal wasn’t a completely benign proposition. I miss that guy.
You can also make an electrostatic generator from dripping water
The water drops if set up right can strip electrons and cause a spark
This has caused explosive results because the same effect works on liquid gases like propane and butane.
The same effect also produces lightning
Yeah, like the https://en.wikipedia.org/wiki/Kelvin_water_dropper
I made one of these, with help from my dad, as a science fair project in the 60’s. It was quite astounding to see a tiny neon bulb flashing at each discharge, powered only by the dripping of water through the copper rings. It was the science fiction that I had just begun to love, brought home to me!
Every child played with a plastic ruler rubbed on their clothes to attract bits of paper…
at least that’s what I did.
And then a little later I went to a Van de Graaff Generator concert – we used to call them VDGG.
BTW this article is great.
The trick I remember frequently seeing/doing was rubbing an inflated latex balloon on a person’s hair then sticking the balloon to a wall.
Up in the mountains on a freezing and bone dry evening and pitch black too, I went to pull the sheet over my head and discovered I had, for lack of a better term, lightning fingers. Dragging my nails across the sheet produced big (several cm) lightning bolts from all my fingers. Felt like I was Thor himself. Never been able to replicate that again though.
There is very little humidity in the air out in the mountains so charges get trapped on surfaces. I have once built a Kelvin water dropper. It worked beautifully in the winter but in the summer it struggled to make visible sparks even in a cool air conditioned environment. I don’t really understand the mechanism of charge dissipation but empirically water vapour plays a huge role.
I had a fuzzy poly something blanket with lions on it in the 80s that had amazing electrostatic capabilities. I would pile it up in a lump on the floor, kneel and bow my head, shake it back and forth a few times and reach out and throw bolts from my fingers that would stretch 3-5 cm and they werent just straight sparks but rather miniature lighting with branches and all. Ive never found another blanket that had that much potential.
its funny how much amusement that blanket provided in a time when the 4 TV stations went off air every night and the net was a tool for catching fish.
How to create Ball lightning: put an amber collar on a cat
Always a favorite: https://www.mos.org/visit/live-presentations/lightning
I was pretty in to electrostatics when I was young. Built an itty-bitty van de Graff in 6th grade (worked!), and one of A.D. Moore’s “DiRod” generators in 9th grade (didn’t work :-( ) Recently bought a mini-Wimshurst machine made from CD player parts (also works!)
It was somewhat after university that I realized that all of the material I’d read about electrostatics (mostly the Moore) was very … qualitative: “charges here induce opposite charges there”, but NO NUMBERS! Has anyone ever seen any more formal treatment? Even “increasing the dielectric constant of this gap here has this effect” or similar…
Might be some quantitative info in this study:
Groundbreaking Study Finally Reveals How Rubbing Generates Static Electricity
September 20, 2024
https://scitechdaily.com/groundbreaking-study-finally-reveals-how-rubbing-generates-static-electricity/
This site is a great resource. https://www.coe.ufrj.br/~acmq/electrostatic.html At the bottom there is a Wimshurst calculator. Electrostatics are very complicated compared to normal electric systems because the air ionises and conducts, and insulators carry surface charge, and surface moisture which leaves them slightly conductive at extremes. On the face of it Wimshursts can be modelled as variable capacitances interacting, but at high voltage the glass carries more surface charge than the plates (like a Bonetti), the position of the neutralising brushes is blurred by corona discharge, and both air and insulators leak charge away in a humidity dependent way.
https://web.archive.org/web/20240927205654/http://amasci.com/weird/unusual/e-wall.html Did anyone ever follow up on this?
Back in the Land of Ago, Mr. Wizard’s Science Secrets showed an impressive means of demonstrating static electricity that I used to advantage on my younger siblings. Have sibling stand on two glass pieplates, four glasses, other good insulators. Strike sibling on the back dozens of times with a piece of fur—striking siblings was part of the fun. Have sibling bring finger close to metal pipe or other ground. A hundred slaps on the back could generate a 1″ spark. One younger brother actually enjoyed the demo and wanted it repeated.