The history of science and technology is a constant evolution of discoveries and improvements. A great example of this is electrostatic machines or generators. In this short essay we are going to see the history of electricity chronologically through discoveries related to electrostatics and their technical applications, especially in the form of generators, since it was discovered that rubbing amber attracted certain objects and it was not well known why even the most modern generators that are now obsolete machines that are used for teaching and recreational physics games.
An electrostatic generator is capable of generating high voltages but with very small currents.. They are based on friction, from mechanical energy that we have to contribute to achieve friction in two materials, one part is transformed into heat and the other into electrostatic energy.
Ancient Greece. The beginnings.
There are references to the attraction of objects by amber after rubbing it with cloth or skin, but it did not go beyond there. No one thought that this attraction could be generated continuously and put to practical use.
As I said, the effect is described but not investigated further. There will be no major advances in this field until the seventeenth century with William Gilbert and Otto von Guericke and especially in the XNUMXth century thanks to the works of Franklin, Priestlye and Coulomb.
Effects related to electricity, from fish that gave discharges, to lightning, have been detailed since ancient Egypt, but no one had understood these phenomena or related them. They were a mystery.
In 585 BC, the Greek philosopher Thales of Miletus studied the properties of the lodestone that attracted iron comparing it with that of amber that attracts many types of objects. He was the first to cite this property of amber. In Greek, amber is Elektron.
XNUMXth century the revolution begins
Here the matter begins to take off. They begin to make more and more discoveries related to electricity with a fever pitch in the second half of the XNUMXth century.
William Gilbert in 1600 found that rock crystal and some gems also attract objects, such as amber, when rubbed. He called all these substances electrical because they had the same properties as amber that as we have said in Greek it was said Elektron and the phenomenon was called electricity. This expression appears in his famous book De Magnete.
We already have our beloved electricity here. Since this electricity seemed to remain in bodies if there was no variation to modify them, it was called static electricity.
William Gilbert also invented the electroscope a tool that lets you know if a body is loaded or not
En el blog How to make a homemade electroscope
The Sulfur Ball by Otto von Guericke
In 1660 Otto von Guericke (1602-1686), famous for his vacuum experiments and for inventing the air pump in 1645, invented the first simple electrostatic generator. It consisted of a ball or globe of sulfur that rotated around an axis with a crank and generated electricity by rubbing against the hand.
It could be charged and unloaded indefinitely and even managed to produce sparks with its electrified ball.
Guericke made his ball by pouring molten sulfur into a hollow glass sphere. After the sulfur cooled, the glass mold was broken. They would later discover that the glass sphere itself achieved the same results on its own.
Hauksbee Mercury Discharge Lamp and Generator
Scientific research continues and the first really practical use appears.
In 1706 this English physicist built a crystal sphere that rotated with a crank and that through friction generated an electrical charge greater than that of the sulfur ball.
It had been observed that if the mercury barometric device invented by Evangelista Torricelli was shaken and the empty part was looked at in the dark, it emitted light. So in 1730 Francis Hauksbee, invented the first mercury gas discharge lamp. He designed a machine that consisted of a rotor to rub a small amber disk in a vacuum chamber and when there was mercury vapor in that chamber, it ignited.
As I have told in the section on the sulfur ball, the glass mold worked just as well as sulfur to make an electrostatic generator. So Winkler set up his electrostatic machine using beer glasses as a rotor (I have only found this anectode in a web and I have not been able to contrast the information. I leave it because it seems curious and credible to me, but take it carefully)
Electrostatic electricity and its machines became a toy that people wanted to experiment with in the XNUMXth century. People wanted to feel an electric shock and devices such as the «the electric kiss«, Where a couple was placed on platforms so that they were charged with static electricity and when they kissed a spark would jump.
And as always the charlatans appeared who took advantage of people claiming that they could cure diseases with electric shocks. As they did with the magnetic properties and nowadays they do with all kinds of products, stones, bleach and others. Mankind has never been saved from the picaresque and scammers.
In 1745, Ewald Jürgen von Kleist (1700-1748) invented the Leyden bottle or Leyden jar. While trying to find a way to store electrical energy, it occurred to him to use a bottle filled with water or mercury. The following year, independently, the physicist Cunnaeus arrived at the same solution in Leyden, in the Netherlands. This is the name we currently know for the invention.
The Leyden bottle is the forerunner of capacitors and from its study and innovation these elements arose. After studying which substances were better to store energy inside the bottle, they realized that if you left the bottle empty and added a layer of metal inside and outside the bottle, electrostatic energy was also stored.
And this is already a condenser current. Two metal sheets separated by a dielectric.
And so we come to the first known victim and recordsIt is due to electrocution (not counting people killed by lightning strikes, of course). To achieve higher charges they began to connect several bottles of Leyden forming a battery.
And although the French abbot Nollet had shown that small animals such as birds and fish died instantly from the discharge of a Leyden jug, no one imagined the danger that this new energy with which they played could entail.
On August 6, 1783 in Saint Petersburg, Professor Richman and his assistants were struck by lightning from charging capacitors. Nothing happened to the assistant but Richman died immediately. The medical report said:
He only had a small hole on his forehead, a burned left shoe, and a blue stain on his foot. […] The brain was fine, the front part of the lung healthy, but the back part was brown and black with blood.
How to build a bottle of homemade Leyden.
Benjamin Franklin and the lightning rod
Possibly the best known electrostatic story is that of Benjamin Franklin and his stormy day comets. Benjamin Franklin was a fan of Leyden bottles.
He proposed that when there was an excess of electric fluid it will be called positive electricity and when there was deficiency, negative electricity.
Observing how the Leyden bottles were discharged, he observed that when exhausted it emitted a spark very similar to a sound, a snap, similar to thunder.
In 1745 he began his experiments on electricity. He had the intuition that lightning was an electric charge and wanted to prove it.
In 1751 he flew a kite with a metal tip in a storm, it was attached to a silk thread. At the end, near Franklin, there was a second string with a metal key. He came to store energy from lightning in Leyden bottles.
He quickly found a practical application for his experiences, lightning rod. He had observed that the bottles were discharged earlier if they had a needle, and since he had concluded that the rays were going to the buildings and were charged, he thought about putting a pointed metal rod and connecting it to the ground so that it would be discharged.
In 1752 he published his ideas in Poor Richard's Almanac and it was a success because lightning rods were installed in buildings.
In 1785 he enunciated his famous law.
From their experiences it was deduced that the force exerted between two electric charges at rest (electrostatic), located in a vacuum and whose dimensions are small compared to the distance that separates them, have the following characteristics (for loads that are punctual):
- It acts in the direction of the line that joins both charges.
- It is attractive if the charges are distinguishable and repulsive if they are the same
- It is proportional to the product of the quantities of the loads
- It is inversely proportional to the square of the distances that separate them.
In the International System of Units, the unit of electric charge is the coulomb (C) which is defined starting from the fundamental unit of current intensity I which is the Ampere (A)
Disc rotor and stack
In 1800 the first disk-based generators. Your inventor was Winter, the hand is replaced by a leather cushion prepared with mercury for friction, thus achieving a more continuous result.
At the same time, about 1799, the first electrolytic experiments were conducted donThe same or better result was obtained than with Leyden bottles.
En 1800 Alessandro Volta unveiled the first electric battery, the voltaic battery That was a complete revolution since it overcame many of the problems dela electrostatics and allowed to generate energy continuously and at will. I will deal with the chronology of the history of chemical batteries in another essay.
Electric Generator and Faraday Cage
In 1836 Faraday discovered this phenomenon by which the electromagnetic field inside a conductor in equilibrium is zero.
Today this concept is used as surge protection in many radios, hard drives, television sets, repeaters, and to protect electronic equipment on airplanes from being burned by lightning.
Previously in 1831 he had invented the direct current electric generator, A dynamo. He discovered that if we move a closed circuit in a magnetic field an electromotive force is generated.
The Wimshurst Machine
They are the most advanced electrostatic disc generators and they represent the pinnacle of this type of machine that little by little was being relegated to scientific curiosity and a toy for children.
It is a generator of electrical charges by electrostatic induction. In this section, generators of this type were developed by Wilhelm Holtz (1865 and 1867), August Toepler (1865), and J. Robert Voss (1880). But they were less efficient machines and with a tendency to change a lot in polarity.
The Wimshurst machine solved all of these problems. Voltages of 200.000 to 300.000 volts are achieved.
Very good results were obtained and they were used to feed X-ray tubes.
En el blog How to make a Wimshurst machine
The Ruhmkorff induction coil
In 1857 Heinrich Daniel Ruhmkorf invented the induction coil, a kind of transformer that allows sending high voltage pulses from low voltage direct current.
This discovery was the one that began to relegate all electrostatic machines. It made them obsolete.
The Van De Graaff generator
We take a timeskip and go to 1931, Robert Van de Graaff invents the generator that bears his name to generate high voltages of the order of 20 million Volts to accelerate particles in the laboratory .. In his first model he reported 1,5 million Volts.
It is a direct current generator. Sends the charges down the belt to a hollow element, usually a sphere.
The highest potential sustained by a Van de Graff accelerator is 25.5 MV, reached by Tandem at "Holifield Radioactive Ion Beam Facility" at "Oak Ridge National Laboratory"
In Ikkaro How to make a generator Van de graaff
The electrostatic steam generator
I want to cite this generator because its operation is based on a different principle than what we have seen so far.
Moist steam that is pressed through a nozzle causes an electrical charge. These were machines that were difficult to maintain and very expensive, but they gave good results in their day.
Electricity has had great technical and theoretical advances from the seventeenth century to the present day. Being the second half of the XIX century an engineering apotheosis with hundreds of advances and modifications.
In this test we have followed the evolution of static electricity through the electrostatic generators that were manufactured. From its discovery until the last generators.
As you may have seen, although I have mentioned it, I have not gone into electric batteries, electrolysis, or the generation of direct and alternating current, the war of currents, or a great variety of topics related to the history of electricity. , but it is such a broad topic that I wanted to narrow it down by focusing on electrostatics, which, let's say, is the first stage since the discovery of electricity.
If you see that I have left an important point in the field of electrostatics or the inventors, engineers and scientists who studied it, do not hesitate to leave me a comment.
- History and chronology of science and discoveries. How science has shaped our world. Isaac Asimov. Ed. Ariel
- Physics Lessons. Volume III. José Luis Manglano de Mas