Charging by Friction Static Electricity - Lesson 2 - Methods of Charging Charging by Friction Grounding - the Removal of a Charge In Lesson 1 , it was explained that atoms are the building blocks of matter. Furthermore, it was explained that material objects are made of different types of atoms and combinations of atoms. The presence of different atoms in objects provides different objects with different electrical properties. One such property is known as electron affinity. Simply put, the property of electron affinity refers to the relative amount of love that a material has for electrons. If atoms of a material have a high electron affinity, then that material will have a relatively high love for electrons. This property of electron affinity will be of utmost importance as we explore one of the most common methods of charging - charging by friction or rubbing. Suppose that a rubber balloon is rubbed with a sample of animal fur. During the rubbing process, the atoms of the rubber are forced into close proximity with the atoms of the animal fur. The electron clouds of the two types of atoms are pressed together and are brought closer to the nuclei of the other atoms. The protons in the atoms of one material begin to interact with the electrons present on the other material.

Amidst the sound of crackling air, you might even be able to hear the atoms saying, "I like your electrons." And of course, the atoms of one material - in this case, the atoms of rubber - are more serious about their claim for electrons. As such, the atoms of rubber begin to take electrons from the atoms of animal fur. When the rubbing has ceased, the two objects have become charged. The procedure of rubbing a rubber balloon against your hair is quite easily performed. You might try it now if you've never performed it. When done, you will likely notice that the rubber balloon and your hair will attract each other. On a dry day, you might even be able to let go of the balloon and have it adhere to your hair. (You will also probably notice that the procedure will initiate a bad hair day. Sorry.) This attraction between the two charged objects is evidence that the objects being charged are charged with an opposite type of charge. One is positively charged and the other is negatively charged. How does this happen? How does the simple rubbing together of two objects cause the objects to become charged and charged oppositely?

How Charging by Friction Works The frictional charging process results in a transfer of electrons between the two objects that are rubbed together. Rubber has a much greater attraction for electrons than animal fur. As a result, the atoms of rubber pull electrons from the atoms of animal fur, leaving both objects with an imbalance of charge. The rubber balloon has an excess of electrons and the animal fur has a shortage of electrons. Having an excess of electrons, the rubber balloon is charged negatively. Similarly, the shortage of electrons on the animal fur leaves it with a positive charge. The two objects have become charged with opposite types of charges as a result of the transfer of electrons from the least electron-loving material to the most electron-loving material. Frictional charging is often demonstrated in Physics class. Two rubber balloons can be suspended from the ceiling and hung at approximately head height. When rubbed upon a teacher's head, the balloons became charged as electrons are transferred from the teacher's fur to the balloons. Since the teacher's fur lost electrons, it became positively charged and the subsequent attraction between the two rubbed objects could be observed. Of course, when the teacher pulls away from the balloons, the balloons experienced a repulsive interaction for each other.

As mentioned, different materials have different affinities for electrons. By rubbing a variety of materials against each other and testing their resulting interaction with objects of known charge, the tested materials can be ordered according to their affinity for electrons. Such an ordering of substances is known as a triboelectric series. One such ordering for several materials is shown in the table at the right. Materials shown highest on the table tend to have a greater affinity for electrons than those below it. Subsequently, when any two materials in the table are rubbed together, the one that is higher can be expected to pull electrons from the material that is lower. As such, the materials highest on the table will have the greatest tendency to acquire the negative charge. Those below it would become positively charged. The Law of Conservation of Charge The frictional charging process (as well as any charging process) involves a transfer of electrons between two objects. Charge is not created from nothing. The appearance of negative charge upon a rubber balloon is merely the result of its acquisition of electrons. And these electrons must come from somewhere; in this case, from the object it was rubbed against. Electrons are transferred in any charging process. In the case of charging by friction, they are transferred between the two objects being rubbed together.

Prior to the charging, both objects are electrically neutral. The net charge of the system is 0 units. After the charging process, the more electron-loving object may acquire a charge of -12 units; the other object acquires a charge of +12 units. Overall, the system of two objects has a net charge of 0 units. Whenever a quantity like charge (or momentum or energy or matter) is observed to be the same prior to and after the completion of a given process, we say that the quantity is conserved. Charge is always conserved. When all objects involved are considered prior to and after a given process, we notice that the total amount of charge amidst the objects is the same before the process starts as it is after the process ends. This is referred to as the law of conservation of charge. Check Your Understanding Use your understanding of charge to answer the following questions. When finished, click the button to view the answers. 1. During a physics lab, a plastic strip was rubbed with cotton and became positively charged. The correct explanation for why the plastic strip becomes positively charged is that ... a. the plastic strip acquired extra protons from the cotton. b. the plastic strip acquired extra protons during the charging process. c.

protons were created as the result of the charging process. d. the plastic strip lost electrons to the cotton during the charging process. Answer: D When two different materials are rubbed together, there is a transfer of electrons from one material to the other material. This causes one object to become positively charged (the electron loser) and the other object to become negatively charged (the electron gainer). 2. Saran Wrap has a larger electron affinity than Nylon. If Nylon is rubbed against Saran Wrap, which would end up with the excess negative charge? ____________ Explain. Answer: Saran Wrap When two materials are rubbed together, the material with the greatest affinity for electrons is the material which takes electrons away from the other material. Saran wrap takes electrons from nylon and acquires the negative charge. In turn, the nylon loses electrons and becomes charged positively. 3. A physics teacher rubs a glass object and a felt cloth together and the glass becomes positively charged. Which of the following statements are true? Circle all that apply. a. The glass gained protons during the rubbing process. b. The felt became charged negatively during this rubbing process. c. Charge is created during the rubbing process; it is grabbed by the more charge-hungry object. d.

If the glass acquired a charge of +5 units, then the felt acquires a charge of -5 units. e. This event violates the law of conservation of charge. f. Electrons are transferred from glass to felt; protons are transferred from felt to glass. g. Once charged in this manner, the glass object and the felt cloth should attract each other. h. In general, glass materials must have a greater affinity for electrons than felt materials. For A: protons are not transferred in electrostatics. For C: charge is neither created nor destroyed (ever). For E: electrons are simply transferred, consistent with the law of conservation of charge. For F: protons are not transferred in electrostatic experiments (the electrons are transferred). For H: If glass transfers electrons to felt, then the felt must be more electron-hungry. 4. Which statement best explains why a rubber rod becomes negatively charged when rubbed with fur? a. The rubber that the rod is made of is a better insulator than fur. b. The fur is a better insulator than the rubber. c. Molecules in the rubber rod have a stronger attraction for electrons than the molecules in the fur. d.

Molecules in the fur have a stronger attraction for electrons than the molecules in the rubber rod. Answer: C During a charging by rubbing (or by friction) process, the material that becomes negatively charged does so because it simply likes electrons more than the material with which it is rubbed. The conductive abilities of the two materials has nothing to do with the subsequent result of the rubbing process. What is static electricity and what causes it?- Explain that Stuff Tweet by Chris Woodford . Last updated: December 1, 2016. Zap! When a bolt of lightning leaps to the ground, we get a sudden, very vivid demonstration of the power of static electricity (electrical energy that has gathered in one place). Most of us know that static builds up when we rub things together, although that's not really a satisfying explanation. What is it about rubbing things that produces an electrical phenomenon? Although lightning is a spectacular example of static electricity, it's not something we can harness. But there are many other places where static electricity is incredibly useful; from laser printers and photocopiers to pollution-busting power plants, static can be really fantastic. So let's take a closer look at what it is and how it works!

Photo: A lightning bolt is a huge release of static electricity, in which built-up electrical potential energy shoots from the sky to the ground in a sudden, improvised, electric current. Picture by David Parsons courtesy of US DOE/NREL (Department of Energy/National Renewable Energy Laboratory) . What is static electricity? Photo: Classic static: When you rub a balloon on your pullover, you create static electricity that makes it stick. The rubbing shifts electrons from your pullover (which becomes positively charged) to the latex rubber in the balloon (which becomes negatively charged). The opposite charges make the two things stick. We take electricity for granted: it's easy to forget that homes, offices, and factories have been powered in this clean and convenient way only since the end of the 19th century—which, in the broader run of human history, is no time at all. It was during the 19th century that pioneers such as Alessandro Volta , Michael Faraday , Joseph Henry , and Thomas Edison figured out the secrets of electricity, how to produce it, and how to make it do useful things.

Before that, electricity was largely a curiosity: it was very interesting for scientists to study and play with, but there wasn't much else they could do with it. In those days, people cooked and heated their homes using wood or coal stoves and lit their rooms with candles or oil lamps; there were no such things as radios or TVs , much less cellphones or computers . The "modern electricity" that powers everything from the phone in your pocket to the subway you ride to school or work is what we call current electricity (or electric current). It's energy that travels down a metal wire from the place where it's produced (anything from a gigantic power plant to a tiny battery ) to the thing it powers (often an electric motor , heating element , or lamp ). Current electricity is always on the move, carrying energy from one place to another. Photo: Current electricity: When electricity flows around a closed loop, called a circuit, we can use it to transport energy from a source (in this case, an electricity outlet on the wall) so it does something useful (in this case, warming the heating elements on an electric fire). Before the 19th century, the only kind of electricity people really knew about or tried to use was static electricity.

The ancient Greeks understood that things could be given a static electric "charge" (a buildup of static) simply by rubbing them, but they had no idea that the same energy could be used to generate light or power machines. One of the people who helped to make the connection between static and current electricity was American statesman, publisher, and scientist Benjamin Franklin . In 1752, when Franklin tried to figure out the mysteries of electricity, he famously did so by flying a kite in a thunderstorm to catch himself some electrical energy (an extremely dangerous thing to do). A lightning bolt zapped down the kite to the ground and, had Franklin not been insulated, he might well have been killed. Franklin realized that static electricity, accumulating in the sky, became current electricity when a lightning bolt carried it down to the surface of the Earth. It was through research such as this that he developed one of his most famous inventions , the lightning rod (lightning conductor). Franklin's work paved the way for the electrical revolution of the 19th century—and the world really changed when people such as Volta and Faraday, building on Franklin's discoveries, learned how to produce electricity at will and make it do useful things.

Potential and kinetic energy Just quickly, in passing, it's worth noting that there's another way to think of static and current electricity and to relate them to things we already know about energy . We can think of static electricity as a kind of potential energy: it's stored energy ready and waiting to do something useful for us. In a similar way, current electricity is (loosely speaking) analogous to kinetic energy: energy in movement—albeit of an electrical kind. Just as you can turn potential energy into kinetic energy (for example, by letting a bolder roll down a hill), so you can turn static electricity into current electricity (that's what a lightning bolt does) and back again (that's how a Van de Graaff generator works). What makes static electricity? Until a few years ago, scientists were confident that they understood static electricity and exactly how it worked. The explanation went like this... Just like the ancient Greeks, we tend to think static electricity comes from rubbing things. So if you live in a home with nylon carpets and metal doorknobs, you'll soon learn that your body builds up a static charge when you walk across the floor, which can discharge when you touch a doorknob, giving you a tiny electric shock.

In most school experiments, we also learn about static by rubbing things. You've probably tried that trick where you rub a balloon on your clothes to make it stick? You might conclude from this that static electricity is somehow connected to friction—that it's the very act of rubbing something vigorously that produces a buildup of electrical energy (in the same way that friction can produce heat and even fire). The triboelectric effect It's not the rubbing that's important but the fact that we're bringing two different materials into contact. Rubbing two things together vigorously simply brings them into contact again and again—and it's this that produces the static electricity through a phenomenon known as triboelectricity (or the triboelectric effect). All materials are built from atoms , which have a positive central core (the nucleus) surrounded by a kind of fuzzy "cloud" of electrons, which are the really exciting bits. Now some atoms have a more powerful pull on electrons than others; a great deal of chemistry stems from that fact. If we put two different materials in contact, and one attracts electrons more than the other, it's possible for electrons to be pulled from one of the materials to the other.

When we separate the materials, the electrons effectively jump ship to the material that attracts them most strongly. As a result, one of the materials has gained some extra electrons (and becomes negatively charged) while the other material has lost some electrons (and becomes positively charged). Hey presto, we have static electricity! When we rub things together again and again, we increase the chances that more atoms will take part in this electron-swap, and that's why a static charge builds up. Photo: How the triboelectric effect explains static electricity: 1. Ebonite (hard vulcanized rubber—shown here as a black rod) and wool (shown as gray) normally have no electric charge. 2) Put them in contact and the ebonite attracts electrons from the wool. 3) Separate them and the electrons remain on the ebonite, making it negatively charged and leaving the wool with a lack of electrons (or a positive charge). Rubbing the two substances together increases the contact between them and makes it more likely that electrons will migrate from the wool to the ebonite. The negative charge on the ebonite is exactly the same size as the positive charge on the wool; in other words, no net charge is created.

The triboelectric series If you experiment with different materials, you find some gain positive charges when they're rubbed and some gain negative charges; some materials also gain more charge than others. It turns out that we can rank materials in order according to the charge they gain, giving us a kind of league table of materials running from positive to negative. Different books and web pages show slightly different lists, but they all broadly run from minerals (positive) through such things as wood and paper (neutral) to plastics (negative). Don't worry too much about the exact order of the list; it's going to vary for all kinds of reasons (the kind of glass or the additives in the latex, for example). ++++++++ POSITIVE ++++++++ − Ebonite (very hard vulcanized rubber) −−−−−−−−NEGATIVE−−−−−−−− This list is called the triboelectric series. The further apart two materials are in the series, the more static electricity will build up when you rub them together. If two materials are very close in the series, it's hard to get them to build up any charge at all no matter how hard you rub them.

That would seem to confirm that static electricity isn't about rubbing, per se, but about the nature of the materials we bring into contact. Rethinking static electricity What you've just read is the traditional, widely accepted explanation of static electricity—and you'll still find it described that way in most school books. But in 2011, scientists reported some important new discoveries that seemed to suggest much more was going on. Instead of being purely a matter of physics, and a simple transfer of charged electrons from one material to another, it seemed static electricity could also be caused by chemistry (movement of ions and other essentially chemical processes). And it could also happen through a swapping of small amounts of actual material (a bit of balloon shifting to your pullover or vice versa). Where we used to think of static as a simple "pile" of negative or positive charge (electrons or a lack of them), on closer inspection, it now appears to be a "mosaic" of both positive and negative charges that add up to an overall charge (positive or negative).

This research is very new, and still evolving, but it seems clear that our traditional explanation of static electricity is an oversimplified version of what's really happening, even if we've faithfully believed it for over 2000 years! Artwork: Top: The traditional theory sees a static charge on a balloon as an even spread of charged particles across its surface. Bottom: According to the latest thinking, a static charge is actually a random "mosaic" of much bigger charges, which can be both positive and negative, and which add up to an overall charge. In this case, there's much more negative charge than positive (yellow than red), so our balloon has an overall negative charge. Further reading A Shocking New Understanding of Static Electricity by Douglas Main. Popular Mechanics, June 29, 2011. More complex articles The Mosaic of Surface Charge in Contact Electrification by H. T. Baytekin, A. Z. Patashinski, M. Branicki, B. Baytekin, S. Soh, and B. A. Grzybowski. Science, July 15, 2011, Vol.

333, Issue 6040, pp.308–312. Antioxidants dispel static electricity by Richard Van Noorden. Nature, September 19, 2013. What Creates Static Electricity? by Meurig W. Williams. American Scientist, Volume 100, July/August 2012, pp.316–323. What use is static electricity? Now static electricity is all very interesting, but what possible use is it? You can't make toast from a lightning bolt and you can't charge your cellphone simply by rubbing its case on your pullover. You might think static is one of those fascinating but ultimately quite useless bits of science that has no practical applications—but you'd be wrong: static electricity is used in all kinds of everyday technology! Laser printers and photocopiers use static electricity to build up ink on a drum and transfer it to paper . Crop spraying also relies on static electricity to help herbicides stick to the foliage of plants and distribute themselves evenly over the leaves. Factory paint-spraying robots use a similar trick to ensure that paint droplets are attracted to metal car bodies and not the machinery around them.

In many power plants and chemical factories, static electricity is used in smokestacks to scrub away pollution (read more in our article on electrostatic smoke precipitators ). Photo: How can you stop air pollution spewing out from smokestacks? One way is to give a static electric charge to smoke, then funnel it through a grid of metal plates with an opposite charge, so the dirty soot particles are removed. That's how "scrubbers" (electrostatic smoke precipitators) work, such as the ones installed in these smokestacks at the McNeil biomass power plant in Burlington, VT. Photo by Warren Gretz courtesy of US DOE National Renewable Energy Laboratory (NREL) . Of course, static electricity has its drawbacks too. It can cause sparks and explosions in fuel depots and stray static is a real nuisance if you're working with electronic components. That's why engineers and chemists have developed all kinds of anti-static technologies (from simple wires to ingenious, slightly conducting paints and coatings) that prevent static buildup in sensitive places. While you're reading these words, you can be sure that someone, somewhere is trying to find a new way to harness static electricity or a better way to stop it causing problems.

Static electricity may be stationary, but it's never standing still! E&M History THE ONE FLUID THEORY OF ELECTRICITY 1. A person standing on wax, and rubbing a tube, and another person on wax drawing the fire; they will both of them, provided they do not stand so as to touch one another, appear to be electrified to a person standing on the floor; that is, he will perceive a spark on approaching each of them with his knuckle. 2. But if the persons on wax touch one another during the exciting of the tube, neither of them will appear to be electrified. 3. If they touch one another after the exciting of the tube and drawing the fire as aforesaid, there will be a stronger spark between them than there was between either of them and the person on the floor. 4. After such a strong spark neither of them discover any electricity. These appearances we attempt to account for thus: We suppose, as aforesaid, that electrical fire is a common element, of which every one of these three persons has his equal share before any operation is begun with the tube.

A, who stands upon wax, and rubs the tube, collects the electrical fire from himself into the glass; and his communication with the common stock being cut off by the wax, his body is not again immediately supplied. B, who stands upon wax likewise, passing his knuckle along the tube, receives the fire which was collected from the glass by A; and his communication with the common stock being cut off, he retains the additional quantity received. To C standing on the floor, both appear to be electrified; for he, having only the middle quantity of electrical fire, receives a spark upon approaching B, who has an over quantity, but gives one to A, who has an under quantity. If A and B approach to touch each other, the spark is stronger; because the difference between them is greater. After such touch, there is no spark between either of them and C, because the electrical fire in all is reduced to the original equality. If they touch while electrising, the equality is never destroyed, the fire only circulating. Hence have arisen some new terms among us. We say, B (and bodies alike circumstanced) is electrised positively; A, negatively; or rather B is electrised plus, A, minus.

And we daily in our experiments electrise plus or minus, as we think proper. To electrise plus or minus, no more needs be known than this; that the parts of the tube or sphere that are rubbed, do in the instant of the friction attract the electrical fire, and therefore take it from the thing rubbing. The same parts immediately, as the friction upon them ceases, are disposed to give the fire, they have received, to any body that has less. In fact, the one-fluid theory gives a coherent account of all these experiments in which a spark passes between people or objects. But it does not give a full explanation of electrostatic attraction and repulsion. It is perhaps plausible that a body with an excess of electrical fluid will attract one with a deficiency, as is indeed observed. Furthermore, two bodies, each with an excess of electrical fluid, will repel each other. It is more difficult to understand why two bodies each having a deficiency of the fluid will repel each other. Why should lack of fluid causes a force? This is explained naturally in our present picture, a two "fluid" model, in which ordinary material contains both positive and negative charges, normally in exact balance.

The negative charges -- electrons -- are light and mobile, and rubbing together two appropriate materials (such as glass and silk) causes some electrons to transfer from one material to the other, leaving electrical charge out of balance in both materials. Consequently, if either of the two materials comes in contact with a third material, the electrical imbalance will tend to cause a flow of electrons into or out of the third material. However, there are some substances, called insulators, which electrons cannot pass through readily. Wax is one example. Franklin's experiments succeeded because he had everyone standing on blocks of wax, so excess electrons could not escape, and a material deficient in electrons was prevented from capturing any. Thus the charge imbalance generated by the rubbing was preserved for a considerable time. (Eventually, charge escapes through the thin layer of moisture that forms on all surfaces if there is any humidity in the atmosphere. This is why electrostatic effects, like sparks, are so much more noticeable in winter, in a heated room, where the air is very dry.) In a way, Franklin was right -- there is only one moving fluid, the electrons, in all these experiments.

But what he didn't realize was that half of the electrical charge in a body, the positive charge in his own notation, doesn't move around at all, it is fixed in the body. (Actually, when electricity flows through a liquid, as it does in a car battery, both positive and negative charges flow, in opposite directions. But batteries came into the world after Franklin's time.) Joseph Priestley Joseph Priestley was born near Leeds, Yorkshire, England in 1733 to strict Calvinist parents. Early in life he rejected the authority of the established churches, and he became a dissenting minister at 22 (many of the facts recounted here are from the Encyclopaedia Britannica). He taught at a dissenting academy, classics, literature and experimental science, probably the first educator ever to teach experimental science to schoolchildren. He wrote about government, advocating complete religious liberty. As a dissenter, he was sufficiently fearful of state control to be skeptical of any sort of social welfare legislation, even proposals for a national system of education.

His religion evolved to a very broad Unitarianism: he denied the existence of a soul separable from the body, and eventually rejected the divinity of Christ, although he felt Christ was sent as an example of how to live. He espoused the cause of the American colonists, and, later, of the French revolutionaries. All these opinions and convictions made him widely unpopular in England. Priestley made many scientific discoveries. He lived near a brewery, and became interested in the gas that lay over the liquids in fermentation (carbon dioxide). He manufactured the gas by dissolving chalk in acid, and dissolved it in water to produce "an exceedingly pleasant sparkling water" -- the first manufactured soft drink! He also discovered oxygen in 1774 (although it was named by Lavoisier). His contributions to electricity came about as a result of his meeting with Benjamin Franklin, in England, in the 1760's and 1770's.

(Franklin spent a lot of his time in England, representing various American interests, and even considered making his home there until trouble arose.) Franklin told Priestley about an odd result he had found (in 1775, according to the PSSC book), in that if he charged up a metal can, standing on an insulator, and dangled a small cork near it, if the cork was on the outside of the can, it was attracted to it, became charged and bounced off, in the usual way. However, if the cork was lowered inside the can, without touching it, it showed no tendency to move towards the side of the can. Apparently there was no electrical attraction. Priestley gave a brilliant argument as to why this should be so. He recalled that Newton had shown that there is no gravitational force inside a uniform spherical shell of matter (hollow on the inside, like a spherical bubble) because if you take any point inside and consider the gravitational attraction at that point towards a small patch of the bubble, this is exactly cancelled by the attraction towards a corresponding patch at the other end of a line from the first patch through the point.

This only works because the law of gravity is inverse square: the further away patch is bigger in proportion to the square of the distance, so these factors cancel out. Anyway, Priestley knew this argument of Newton's, and he figured that if there was no electrical force inside Franklin's metal can, there was probably no electrical force inside a perfectly spherical charged can either, and for a spherical can you know that the charges will spread themselves evenly, because one place is as good as another. Therefore, a uniform spherical shell of electrical charge will exert no force on a small charge inside it, just like Newton's gravity shell, and it is hard to avoid the conclusion that this means the force between charges has the same dependence on distance as the gravity force, that is, it goes as the inverse square. The inverse square nature of the electrical force was confirmed by Charles Coulomb in 1785 by a direct measure using a torsion balance of the force between two charged conductors. Priestley ended his days in America. On the second anniversary of the Fall of the Bastille (July 14, 1791) there was mob rule in Birmingham, England where Priestley was then living.

They burned down his house, his church and his laboratory. He escaped in disguise. He eventually settled in Northumberland, Pa. Priestley and Jefferson (Reference for this section: Thomas Jefferson, Statesman of Science by Silvio Bedini, Macmillan, New York, 1990, pages 284,285. Cultural remark: note from the description on page 288 that Jefferson's own religious views appear essentially indistinguishable from Priestley's.) (from the above reference) Jefferson had long been contemplating the prospect of a new state university ever since he had made his famous revision of Virginia's laws to reform its educational system. Although his plan to import the faculty of the College of Geneva to Virginia had failed, Jefferson continued to be concerned about the state of higher education in Virginia. He had originally proposed that the College of William and Mary could be revitalized if moved to Albemarle County and modernized. This met with great opposition from those who were concerned with its Episcopal tone so that nothing had come of the proposal. He was ready to try once more, and consulted with Dr. Priestley for assistance in setting up a science curriculum. When Dr.

Priestley, discoverer of oxygen, whose experiments with electricity and gases brought him great renown, left England in 1794, he had established himself in Pennsylvania. However, the persecution which had forced his departure followed him, as Federalists labeled him "atheist" and "Jacobin." To Priestley, Jefferson described the College of William and Mary as "just well enough endowed to draw out the miserable existence to which a miserable constitution has doomed it. It is moreover eccentric in its position, exposed to bilious diseases as all the lower country is, & therefore abandoned by the public care. as that part of the country is in a considerable degree by its inhabitants." His plan was to establish a university in upper Virginia where a healthier location prevailed, and which would be more centrally located in the state. It was to be designed on a liberal and modern plan so that it would attract students from other states as well. To achieve this, it was necessary to develop a good curriculum which included "a judicious selection of the sciences practically grouped together in an institution meant chiefly for use." He felt no one was as familiar with subjects to be taught as Priestley, and for that reason requested his cooperation.

He again consulted Priestley about the teaching of languages, which Jefferson did not consider essential in teaching the sciences except as they might be useful in studying them. "The Gothic idea that we are to look backwards instead of forwards for the improvement of the human mind," he confided to Priestley, "and to recur to the annals of our ancestors for what is most perfect in government, in religion & in learning, is worthy of those bigots in religion & government, by whom it has been recommended, and whose purposes it would answer." Priestley promptly forwarded his "Hints Concerning Public Education." Galvani and Volta The material in this section is largely based on the extracts from Galvani's and Volta's work in A Source Book in Physics, by W. F. Magie. I have also used the account in From Alchemy to Quarks, by Sheldon Glashow, Brooks/Cole 1994. Luigi Galvani (1737-1798), a doctor and anatomy professor at the University of Bologna, no doubt routinely spent a lot of time dissecting animals.

He also had in his laboratory an electrical machine, which charged up a conductor some distance away, which he was using in some electrical researches. One day (around 1790) one of the people working in the lab noticed that on touching a freshly dissected frog's nerve with a metal scalpel, the frog's leg twitched violently, and this occurred if the electrical machine was sparking at the same time. Further investigation revealed that the twitching only occurred if the scalpel (which had a bone handle) was held in such a way that the person holding it was touching the metal part. If the scalpel was replaced by a glass rod, nothing happened, if by an iron rod, the twitching always occurred when the electrical machine sparked. Having established that the frog's legs twitched in response to electrical stimulation from a machine, Galvani wondered if they could be used to detect atmospheric electricity, possibly even when thunderstorms were not present. Therefore he hung prepared frogs with a brass hook through the spinal cord to an iron railing enclosing a garden at his house. He found twitching did occur, but it didn't seem related to thunderstorms.

" ..showed the usual contractions not only when there was lightning but also when the sky was clear and fair, I thought the origin of these contractions might be found in the changes which nevertheless were going on in the atmospheric electricity." But the contractions were few and far between. "Finally, tired of this useless waiting, I began to squeeze and press the hooks which were fastened in the spinal cord against the grating, to see whether such an artifice might excite the contraction of the muscle .." It did! He "quite often" observed contractions on pressing the hook, and it didn't seem to depend on the weather at all! He thereupon decided that maybe his assumption that the twitching was caused by atmospheric electricity was wrong. As Galvani writes, "So easy is it to deceive oneself in experimenting, and to think that we have seen and found that which we wish to see and find." So he moved indoors, laid the animal on an iron plate, pressed the hook which was in the spinal cord against the plate, and, as he says, "behold, the same contractions, the same motions!" He found consistent results from day to day.

He also found that if the brass hook was replaced by an iron hook, the contractions either did not occur or were very small. For some weird reason, it was apparently important to have two different metals. He found zinc and brass to be very effective. He concluded that since the contractions (or twitching) occurred with no electrical machine present, and indoors away from possible atmospheric electricity (and in any case on a calm day), "possibly the electricity was present in the animal itself" (my italics). Of course, Galvani had stumbled on to something important: the nerves do transmit messages from the brain to muscles using electrical impulses. But he believed the electricity was somehow life itself -- and his nephew, Giovanni Aldini, was a real showman. Aldini was awarded the Copley Medal of the Royal Society for apparently reanimating a decapitated felon using an electrical discharge. (Teaching note: as Andy Jackson pointed out to me, Mary Shelley's Frankenstein was inspired by Galvani, and talks about his work in the preface.

Andy did a joint unit on this with the English teacher.) Alessandro Volta (1745-1827) became a professor of physics at the University of Pavia in 1779. He repeated Galvani's experiments, confirmed his results, but came to a different, and startling, conclusion. It might be relevant to mention that both men were in an area recently taken over by Napoleon, Galvani's sympathies were with the old regime, but Volta threw in his lot with the French. Possibly during this period animal electricity seemed like an old superstition -- Mesmer's animal magnetism had been discredited not long before. Anyway, Volta set out to find a non-mystical explanation. To appreciate how clever Volta was, it is important to bear in mind that the whole development of the science of electricity up to this point had consisted of more and more efficient ways of collecting the "electric fluid" from "electric materials" such as amber, glass, etc., and storing it in metals or Leyden jars.

The metals were called non-electric materials -- you couldn't build up a charge by rubbing a piece of metal, the metals were considered passive in electricity, they were handy for transferring electricity from one place to another, but didn't generate it. Volta repeated Galvani's experiments, and in particular noticed that, as earlier noted by Galvani, the twitching, indicating presence of electricity, occurred when two different metals, each touching the other, had their other ends touching the frog. In contrast to Galvani, however, Volta didn't believe the animal itself was the source of the electricity. But that presented the tough question of where the electricity could possibly be coming from. There were no "electric" materials present! In fact, he had few options. The effect was there with just two bits of wire -- one iron, one brass -- and the frog. If it wasn't coming from the frog, it had to be coming from the two pieces of wire. But he couldn't get a spark -- the real indicator of electricity -- from the two pieces of wire. This is where he made the great leap forward.

Having decided that the animal nature of the frog was irrelevant, he took two metal strips (following Galvani, he chose zinc and brass) with cardboard soaked in saltwater between them (more convenient than frog), and to intensify the effect, piled as many as sixty of these sandwiches on top of each other. When he placed a conductor from one end of this "battery" (as he called it) to another, it did produce a spark -- much feebler, he admitted, than that from a Leyden jar, but definitely a spark, and, unlike a Leyden jar, you didn't have to recharge this battery -- you could keep retouching the conductor and it continued to spark. He also constructed what he termed a "crown of cups" a row of (nonmetallic) cups filled with brine, a wire joining a strip of brass in each cup to a strip of zinc in the next, to form a chain. This gave essentially the same results as the pile of plates. Thus Volta invented the battery, which, in contrast to the electrical machines previously developed, provided electric charge in really large quantities, and initiated most of the technological developments that have changed the world so much since that time.

However, Volta himself apparently did not go on to investigate the consequences of a continuous source of electrical charge. In fact, his writing gives the impression that he never used the battery to provide a steady current -- in comparing it to a Leyden jar he calls it "a battery of an immense capacity; but which further infinitely surpasses the power of those batteries (Leyden jars) in that it does not need, as they do, to be charged in advance by means of an outside source; and in that it can give the disturbance every time that it is properly touched, no matter how often." In 1801, Volta was invited to Paris to give three lectures, with demonstrations, on his work, and Napoleon attended them all (Glashow, page 312). Napoleon said that the experiments should be carried out on a larger scale, and later, when Casvy at the Royal Institution in London had a voltaic pile with 2,000 units, Napoleon ordered that piles be constructed at the Ecole Polytechnique, including one bigger than anybody else's.

Electrolysis in England The above quotation from Volta comparing his pile, or battery, to a Leyden jar, is from a letter he wrote from Como on March 20, 1800, to Sir Joseph Banks, then president of the Royal Society. Sir Joseph showed the letter to William Nicholson, a wealthy London businessman who published his own science journal. Nicholson and a friend of his, Sir Antony Carlisle, a surgeon, wasted no time: on April 30, they constructed a Voltaic pile using 17 silver half crowns, zinc plates and pasteboard soaked in salt water. They felt the mild shock, but saw no leaf separation when the pile was connected to a gold leaf electroscope. However, they were able to establish the presence of electrostatic charge by some ingenious mechanism called a doubler.

(This may have been a variable capacitor of some kind: for example, if two very close large parallel plates are connected across the electroscope, on pulling the plates apart the voltage will increase and the leaves diverge.) They went on to see if they could still feel the shock if they connected the two ends of the battery with various substances, and verified that the electricity was indeed able to shock them through metals and a short path through salt water, but not through glass, etc. Here they made an important discovery. Nicholson writes: " ... the contacts being made sure by placing a drop of water on the upper plate, Mr. Carlisle observed a disengagement of gas around the touching wire. This gas, though very minute, evidently seemed to me to have the smell afforded by hydrogen..." They realized that the electricity must be decomposing the water, which they knew to be a combination of hydrogen and oxygen. They also realized that the oxygen would be more difficult to see, because it combined with the metal to form oxide. A week or so later, they set up an experiment with 68 sets of plates in the pile, connected to two platinum (and so noncorroding) wires under water, with inverted tubes filled with water set over the wires.

They ran the experiment for 13 hours, and found the gas on one side displaced 72 grains of water, that on the other 142 grains -- so these are measures of volume. It was already known that by volume two parts of hydrogen combine with one of oxygen to make water, so their decomposition was quantitatively confirmed. The work was published in July, naturally with no trouble, in Nicholson's own journal. They also noticed that the decomposition of the water wasn't the only chemical reaction taking place. In the battery itself, the zinc was being rapidly oxidized. In fact, they note with "some surprise" that on looking back at Volta's account of his work, he fails to mention this. Perhaps this was because Volta never allowed a steady contact to be maintained, so a steady current would flow, but simply drew a series of sparks (?). The Royal Institution After the experiment of Nicholson and Carlisle described above, most of the important British work in understanding electricity took place at the Royal Institution in London.

The Institution was founded in 1799 by Count Rumford, who was born Benjamin Thompson in Woburn, Massachussetts in 1753, and indentured to a Salem merchant at age 13. Over the next few years (info from Glashow's book), he learned some science on his own, became a schoolmaster, became a major in the New Hampshire militia and at the same time a spy for the British. He left rather hastily in 1775 for a job in London. Rumford's major achievement as a physicist was to establish that heat was not a fluid that flowed from hot bodies to cold bodies, and that could perhaps be shaken out of matter by friction or chemical effects. He proved that heat could be produced in indefinitely large amounts by friction, specifically by grinding or boring a gun barrel. This convinced him it couldn't be some fluid being squeezed out of the matter, as many thought, for how could the matter hold an indefinitely large amount? He decided instead that heat was a matter of motion of the microscopic constituents of matter, a view we now know to be correct.

Rumford was a royalist, he didn't believe democracy was a good idea, but he did believe that the royal rulers were bound for trouble if the people were not treated reasonably well. He worked for some years in the kingdom of Bavaria, where he took the homeless from the streets, giving them food and shelter and setting them to work manufacturing military equipment. He reformed the Bavarian army, schooling the soldiers and increasing their salaries. Rumford was a real inventor: in his attempts to keep the army reasonably happy he discovered that trapped air was the crucial element in effective warm clothing, and invented thermal underwear. He also invented the drip coffeepot, the Rumford stove and the pencil eraser (info from Glashow's book). Quoting now from J. D. Bernal's Science in History, "Returning to England he saw at once that the Industrial Revolution could not be a success unless there were some means of training a new type of mechanic who could base himself on science instead of blind tradition.

For that he persuaded the wealthy to put up the money for an institution under royal patronage for: ....diffusing the Knowledge and facilitating the general Introduction of useful mechanical Inventions and Improvements, and for teaching by Courses of Philosophical Lectures and Experiments the applications of science to the common Purposes of Life." This Royal Institution was founded in 1799, and its first director was a young Cornishman, Humphry Davy. Davy was a great showman, but did not consider common mechanics worthy of his brilliance, so the Institution rapidly evolved to presenting lectures for the wealthy, who paid to attend. In Rumford's original plan, there had been a back door through which the poor could access a balcony to hear the lectures from a distance for free. Davy had it bricked up. The Institution did, however, perform a very valuable function in that it was a subsidized science lab (one of the very few in the world) where Davy was able to make many important discoveries in electrochemistry, using very large voltaic piles to electrolyze soda and potash, for example, which had been considered to be elements up to that time. He discovered sodium and potassium, as well as other elements.

Davy also invented the electric arc lamp, which was to be the brightest light for a century or so, and a miner's safety lamp for working in gassy mines. Cultural note from Bernal (p 540). In Davy's introductory discourse as director of the Royal Institution in 1802 (at age 23): The unequal division of property and of labor, the difference of rank and position amongst mankind, are the sources of power in civilized life, its moving causes, and even its very soul. Although Rumford was certainly a Tory, this might have been a bit much even for him (but I'm not sure -- he did quarrel with his co-organizers, and left for the continent about this time. He subsequently married Lavoisier's widow). Davy's philosophy certainly did not accord well with Michael Faraday's views on life, and the two had a very tense relationship over many years. Michael Faraday Books: a good account of Faraday's life and work begins on p 129 in The Great Scientists, Jack Meadows, Oxford 1994 (paperback).

See also Glashow, and Great Experiments in Physics, Morris Shamos, Ed., Dover 1987. Michael Faraday was born in 1791 near London. His father was a blacksmith from the North of England, who moved looking for work at a time of depression. The father had health problems that made work increasingly difficult, so the family was very poor. Young Faraday became an errand boy for a bookbinder and bookseller. Then at age 14, he apprenticed to learn the trade. He read a great deal, and in particular was fascinated by science books. He joined a science club that met weekly. In 1812, one of the bookshop's customers bought him some tickets for Davy's lectures at the Royal Institution. To be continued...(I hope) 1. De Magnete, by William Gilbert, London, 1600. Dover reprint (in English!) available. 2. Opticks, Sir Isaac Newton, London, 1730, Dover edition available. 3. A History of Electricity, by Park Benjamin, Wiley, NY, 1898. 4.

A Source Book in Greek Science, Cohen and Drabkin, Harvard, 1966. 5. A Source Book in Physics, Magie, Princeton, 1935. 6. A History of Electricity, Canby, Hawthorn Books, NY, 1963. 7. History of Western Philosophy, Bertrand Russell, Allen and Unwin, 1957. 8. A History of Science, Dampier, Cambridge 1929 (but 1989 paperback available). (Note in this last, remark p 33 that Aristotle didn't understand density - no-one did before Archimedes - like acceleration, if Aristotle didn't get it, students most likely haven't got it either.) 9. On Galvinism: The Ambiguous Frog sci eng QP341. P4713 (1992) CAUSE Static electricity is generated by an unbalance of the molecular construction of relatively non-conductive insulators such as plastics, paper, glass, ceramics and other non conductive materials. All matter is composed of atoms. A balanced atom contains positive charges that are present in the nucleus of the atom.

An equal amount of negative charges orbits this nucleus in the form of electrons. Both charges are equal and, therefore, the overall charge of a balanced atom is zero. However, should this configuration be disturbed and several electrons removed from this atom, we end up with a greater positive charge in the nucleus and a deficiency of electrons, which gives you an overall charge in the positive direction. Conversely, should we add a few extra electrons, we have an overall charge of negative, due to the fact that we now have an excess of electrons and the net charge is now in the negative direction. See figure below. Some materials such as glass, hair, and Nylon tend to give up electrons and become positively charged. Other materials such as Polypropylene, Vinyl (PVC), Silicon, Teflon, Silicone tend to collect electrons and become negatively charged. The Triboelectric series is a listing of various materials and there tendency to charge positive or negative. CONDUCTIVITY The ability of material to surrender its electrons or absorb excess electrons is purely a function of the conductivity of the material with which you are working. For example, a pure conductor, such as copper, has a rigid molecular construction that will not permit its electrons to be moved about freely.

However, as you approach the semi-conductor range, such as some bond papers, the ability of this material to surrender its electrons is relatively easy and can be accomplished by friction, heat or pressure. As you approach the purely non-conductive materials, such as plastics, glass ceramics, it is extremely easy to disrupt the molecular construction and cause the material to charge with the slightest friction, heat or pressure. If the conductivity of your processed material can be controlled, then, preventing static electricity becomes relatively easy. However if the material is nonconductive static electricity can build up on the material. For example, adding surface conductivity to plastics will move them up into the higher conductivity range and prevent the build up of static electricity that is caused by friction. This is normally accomplished by use of additives such as moisture and anti-static sprays. The average anti-static spray is made up from a soap based material that's been diluted in a solvent, such as mild alcohol. A fire retardant is added to combat flammability of the solvent. A short time after contact with your material, the fire retardant and solvents evaporate leaving you with a conductive coating on the surface of the material.

The plastic has now become conductive and as long as this coating is not disturbed, it will be difficult to generate static electricity in this material. IONIZATION By following the above steps, you can reduce the hazards of building up high charges of static electricity to a point. However the above steps are passive and of limited effectiveness. Also changing a specified material or adding a spray may not be possible or allowed. An active method static control is by ionization. It is important to understand that static electricity cannot be entirely eliminated. In fact, the terminology, "static eliminators," is definitely misleading. Static eliminators are really ionizing units that produce both positive and negative ions to be attracted by the unbalanced material so that neutralization does occur. For example, a charged piece of material can be neutralized by utilizing a static neutralizer. However, it does not eliminate the static electricity because, if the material is again frictioned after being neutralized, static electricity will be generated. In order to gain the most benefit from your static neutralizing or static control equipment, it is important that you understand how they operate and how they provide the means of neutralization.

Most electronic static neutralizers are constructed by placing a high voltage on a sharp point in close proximity to a grounded shield or casing. There are two basic types static control ionizers- AC & DC. With Alternating Current ionizers the high voltage alternates current pulses through the 60 cycle operation, the air between the sharp points and the grounded casing is actually broken down by ionization and therefore both positive and negative ions are being generated. Half of the cycle is utilized to generate negative ions and the other half is utilized to generate positive ions. On 50 or 60 cycles per second power grid polarity is changing ionization every 1/100 or 1/120 of a second. DC ionizers also put a high voltage on a sharp point but need to produce the opposite polarity by a second power supply or some kind of circuitry to switch polarity. Both AC and DC Systems have advantages. The application, cost, performance, space are all factored into deciding the proper type of static control ionizer to use. If the material being neutralized is charged positive, it will immediately absorb negative ions from the static neutralizer and repel the positive ions.

When the material becomes neutralized, there is no longer electrostatic attraction and the material will cease to absorb ions. Conversely, if the material being neutralized is charged negative, it will absorb the positive ions being generated by the neutralizer and repel the negative ions. Again, once neutralization is accomplished, the material will no longer attract ions. See figure below. Nuclear-powered equipment may also be used to generate ionized air for static neutralization. These devices, powered by Polonium 210 isotopes which have a half-life of only 138 days, are continually losing their strength and must be replaced annually. They are more expensive and less effective than electrically powered devices. These nuclear devices cannot be purchased and are leased by users. One year lease costs are usually more than the purchase price of comparable electrically powered devices. D. Select the proper static control equipment to solve the problem. Trouble shooting a static electricity problem, some sort of measuring equipment is helpful. For example, an ElectroStatics, Incorporated Model 9000 electrostatic meter will measure the amount of static electricity that is present and identify the polarity as either positive or negative. Measuring and locating static electricity will remove the mystery often associated with this phenomenon.

Once the problem is identified and goals defined, the solution options should be considered next with the help from the experienced engineers at Electrostatics, Inc . PROBLEM IDENTIFICATION Before any problem can be solved it must be identified. Is your problem related to static electricity? An in-depth analysis should be made with the necessary equipment and experience to identify and solve the problem. Passive Solutions INDUCTION Removing or neutralizing static electricity by induction is the simplest and oldest method. Tinsel or special wire are the most common tools for this application. However, tinsel is oftentimes misused, get dirt and damaged and, therefore, oftentimes not successful. The first thing that must be recognized is the fact that any induction device, such as tinsel, will never reduce or neutralize static electricity to the zero potential level. This is due to the fact that a threshold or beginning voltage is required to "start" the process and that voltage is high. First, the correct induction equipment must be utilized. The induction bar must be well grounded electrically. The induction bar must be stretched tight and placed 1/4 of an inch from the material to be neutralized.

There must be "free air space" under the material to be neutralized directly under or over the spot where you place the tinsel. In this fashion the induction will reduce static electricity on both sides of the static laden material. Actually, if the above steps are utilized, the sharp ends or points of the grounded induction device will ionize the air over the surface being neutralized, because the grounded sharp ends are placed within the electrostatic field that is present due to static electricity. If the static charge is negative in polarity, the electrostatic field is negative and positive ions are generated via the grounded sharp ends of the induction device and the positive ions are attracted back to the static laden surface. Conversely, if the static charge is positive in polarity, negative ions will be generated by the grounding induction device and attracted back to the charged area. Induction does work but is limited to reducing the level of static to a threshold level which usually still very high and usually higher than what is needed to reduce or eliminate problems related to static electricity. Ionization or active static control is the best way to reduce static charge on non conductive surfaces to very low levels.

Question: Static electricity is fundamentally produced by?
Answer: Friction