The Electric Vocabulary

Posted on 2012/01/04


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This article has now been published in Physics Education, and is available to read (for free) here:

James Sheils 2012 Phys Educ 47 78

Below are extracts from a selection of the sources quoted in the article.

Appendix – Original Sources

Extract from Chaper 2 Book 2 of William Gilbert’s “De Magnete” (On Loadstone) (1600)

Celebrated has the fame of the lodestone and of amber ever been in the memoirs of the learned. Lo and also amber do some philosophers invoke when in explaining many secrets their sense become dim and reasoning cannot go further.
But these men (apart from that common error) being ignorant that the causes of magnetical motions are widely different from the forces of amber, easily fall into error, and are themselves the more deceived by their own cogitations.  For in other bodies a conspicuous force of attraction manifests itself otherwise than in loadstone; like as in amber, concerning which some things must first be said, that it may appear what is that attaching of bodies, and how it is different from and foreign to the magnetical actions; those mortals being still ignorant, who think that inclination to be an attraction, and compare it with the magnetick coitions.

Our own age has produced many books about hidden, abstruse, and occult causes and wonder, in all of which amber and jet are set forth as enticing chaff but they treat the subject in words alone, without finding any reasons or proofs from experiments, their very statements obscuring the ting in a greater fog, forsooth in a cryptic, marvellous, abstruse, secret, occult, way.  Wherefore also such philosophy produces no fruit, because very many philosophers making no investigation themselves, unsupported by any practical experience, idle and inert, make no progress by their records, and do not see what light they can bring to their theories; but their philosophy rests simply on the use of certain Greek words, or uncommon ones; after the manner of our Latin gossips and barbers nowadays, who make show of certain Latin words to an ignorant populace as the insignia of their craft, and snatch at the popular favour.

For it is not only amber and jet (as they suppose) which entice small bodies; but Diamond, Sapphire, Carbuncle, Iris gem, Opal, Amethyst, Vincentia, and Bristolla (and English gem or spar), Beryl, and Crystal do the same.
These substance draw everything, not straws and chaff only, but all metals, woods, leaves, stones, earths, even water and oil, and everything which is subject to our sense, or is solid; although some write that amber does not attract anything but chaff and certain twigs; (wherefore Alexander Aphrodiseus falsely declares the question of amber to be inexplicable, because it attracts dry chaff only, and not basil leaves, but these are the utterly false and disgraceful tales of the writers.

But very many electricks (as precious stones and some other substances) do not attract at all unless rubbed.  On the other hand many gems, as well as other bodies, are polished, yet do not allure, and by no amount of friction are the arouse; thus the emerald, agate, carnelian, pearls, jasper, chalcedony, alabaster, porphyry, coral, the marbles, touchstone, flint, bloodstone, emery, do not acquire any power; nor do bones, or ivory, or the hardest woods, as ebony, nor do cedar, juniper, or cyprels; nor do metals, silver, gold, brass, iron, nor any loadstone, though many of them are finely polished substances of which we have spoken before, toward which, when they have been rubbed, bodies incline.(…)For spent air, either blown out of the mouth of given off from moister air, chokes the virtue [of an electrik].  If indeed either a sheet of paper or a piece of linen be interposed, there will be no movement.  But a loadstone, whithout friction or heat, whether dry, or suffused with moisture, as well in air as in water, invites magneticks, even with the most solid bodies interposed, even planks of wood or pretty thick slabs of stone or sheets of metal.

A loadstone appeals to magneticks only; towards electricks all things move.

Extract from Charles Du Fay’s letter to the Royal Society upon carrying out some of Stephen Grey’s experiments.

Du Fay, Charles. (1734) “A letter to the Royal Society Concerning Electricity.”

Phil. Trans. 1733-1734 38, 258-266

Chance has thrown in my way another Principle, more universal and remarkable than the preceding one, and which casts a new Light on the Subject of Electricity.  This Principle is, that there are two distinct Electricities, very different from one another; one of which I call vitreous Electricity, and the otherresinous Electricity.  The first is that of Glass, Rock-Crystal, Precious Stones, Hair of Animals, Wool, and many other Bodies: The second is that of Amber, Copal, Gum-Lack, Silk, Thread, Paper, and a vast Number of other Substances.  The Characteristick of these two Electricities is, that a Body of the vitreous Electricity, for Example, repels all such as are of the same Electricity; and on the contrary, attracts all those of the resinous Electricity; so that the Tube, made electrical, will repel Glass, Crystal, Hair of Animals &c. when render’d electrick and will attract Silk, Thread, Paper, &c. through render’d clectrical likewise.  Amber on the contrary will attract electrick Glass, and other Substances of the same Class, and will repel Gum-Lac, Copal, Silk, Thread, &c. Two Silk Ribbons rendered electrical, will repel each other; two Woollen Threads will do the like; but a Woollen Thread and a Silk Thread will mutually attract one another.  This Principle very naturally explains, why the Ends of Threads, of Silk, or Wool, recede from one another in Form of a Pencil or Broom, when they have acquired an electrick Quality.  From this Principle one may with the same Ease deduce the Explanation of a great Number of other Phenomena.  And ‘tis probable, that this Truth will lead us to the further Discovery of many other things.

In order to know immediately, to which of the two Classes of Electricity belongs any Body whatforever, one need only render Electrical a Silk Thread, which is know to be of the resinous Electricity, and see whether that Body, render’d electrical, attracts or repels it.  If it attracts, ‘tis certainly of that kind of Electricity which I call vitreous; if on the contrary it repels, ‘tis of the same kind of Electricity with the Silk, that is of the resinous.  I have likewise observed that communicated Electricity retains the same Properties: For if a Ball of Ivory, or Wood, be set on a Glass Stand, and this Ball be render’d electrick by the Tube, it will repel all such Substances as the Tube repels; but if it be rendered electrick by applying a Cylinder of Gum-Lac near it, it will produce quite contrary Effects,viz. precisely the same as Gum-Lac would produce.  In order to succeed in these Experiment, ‘tis required that the two Bodies, which are put near one another, to find out the Nature of their Electricity, be rendered as electrical as possible; for if one of them was not at all, or but weakly electrical, it would be attracted by the other, though it be of that Sort, that should naturally be repelled by it.  But the Experiment will always succeed perfectly well, if both the Bodies are sufficiently electrical.

I have several other Methods to discover the Nature of the Electricity any Body is of; but my Letter is already long enough, and my Design was only to give your Grace a very succinct Extract of the Experiment I have hade this last Year.  I beseech your Grace to communicate it to the Royal Society, and in particular to Mr.Grey, who works on this Subject with so much Application and Success, and to whom I acknowledge my self indebted for the Discoveries I have made, as well as for those I may possibly make hereafter; since ‘tis from his Writings that I took the Resolution of applying my self to this kind of Experiments.

Extracts from Benjamin Franklin’s letters to Peter Collinson (1748-1750) Found in Sparks, Jared. (1840) “The works of Benjamin Franklin” Volume V (p. 180-186)

Introductory Letter.
Philadelphia, 28 March, 1747.
Your kind present of an electric tube, with directions for using it, has put several of us on making electrical experiments, in which we have observed some particular phenomena, that we look upon to be new. I shall therefore communicate them to you in my next, though possibly they may not be new to you; as, among the numbers daily employed in those experiments on your side the water, it is probable some one or other has hit on the same observations. For my own part, I never was before engaged in any study that so totally engrossed my attention and my time, as this has lately done; for what with making experiments when I can be alone, and repeating them to my friends and acquaintance, who, from the novelty of the thing, come continually in crowds to see them, I have, during some months past, had little leisure for any thing else.

I am, &.c.

B. Franklin.

Philadelphia, 11 July, 1747.


In my last I informed you that, in pursuing our electrical inquiries, we had observed some particular phenomena, which we looked upon to be new, and of which I promised to give you some account, though I apprehended they might not possibly be new to you, as so many hands are daily employed in electrical experiments on your side the water, some or other of which would probably hit on the same observations.

The first is the wonderful effect of pointed bodies, both in drawing off and throwing off the electrical fire. For example,

Place an iron shot, of three or four inches diameter, on the mouth of a clean, dry glass bottle. By a fine silken thread from the ceiling, right over the mouth of the bottle, suspend a small cork ball, about the bigness of a marble; the thread of such a length, as that the cork ball may rest against the side of the shot . Electrify the shot, and the ball will be repelled to the distance of four or five inches, more or less, according to the quantity of electricity. When in this state, if you present to the shot, the point of a long, slender, sharp bodkin, at six or eight inches distance, the repellency is instantly destroyed, and the cork flies to the shot. A blunt body must be brought within an inch, and draw a spark, to produce the same effect. To prove that the electrical fire is drawn off by the point, if you take the blade of the bodkin out of the wooden handle, and fix it in a stick of sealing-wax, and then present it at the distance aforesaid, or if you bring it very near, no such effect follows; but sliding one finger along the wax till you touch the blade, and the ball flies to the shot immediately. If you present the point in the dark, you will see, sometimes at a foot distance and more, a light gather upon it, like that of a fire-fly, or glowworm; the less sharp the point, the nearer you must bring it to observe the light; and, at whatever distance you see the light, you may draw off the electrical fire, and destroy the repellency. If a cork ball so suspended be repelled by the tube, and a point be presented quick to it, though at a considerable distance, it is surprising to see how suddenly it flies back to the tube. Points of wood will do near as well as those of iron, provided the wood is not dry; for perfectly dry wood will no more conduct electricity than sealing-wax.

We had for some time been of opinion, that the electrical fire was not created by friction, but collected, being really an element diffused among, and attracted by, other matter, particularly by water and metals. We had even discovered and demonstrated its afflux to the electrical sphere, as well as its efflux, by means of little, light windmill-wheels made of stiff paper vanes, fixed obliquely, and turning freely on fine wire axes; also by little wheels, of the same matter, but formed like water-wheels. Of the disposition and application of which wheels, and the various phenomena resulting, I could, if I had time, fill you a sheet, f The impossibility of electrizing one’s self (though standing on wax) by rubbing the tube, and drawing the fire from it; and the manner of doing it, by passing the tube near a person or thing standing on the floor, &c, had also occurred to us some months before Mr. Watson’s ingenious Sequel came to hand; and these were some of the new things I intended to have communicated to you. But now I need only mention some particulars not hinted in that piece, with our reasonings thereupon; though perhaps the latter might well enough be spared.

1. A person standing on wax, and rubbing the 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 electrized, 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 appeared to be electrized.
3. If they touch one another after exciting the tube, and drawing the fire as aforesaid, there will be a stronger spark between them, than was between either of them and the person on the floor.

4. After such 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 the three persons above mentioned has his equal share, before any operation is begun with the tube. A, who stands on 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 on wax likewise) passing his knuckle along near the tube, receives the fire which was collected by the glass from A; and his communication with the common stock being likewise cut off, he retains the additional quantity received. To C, standing on the floor, both appear to be electrized; 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 electrizing, the equality is never destroyed, the fire only circulating. Hence have arisen some new terms among us; we say B (and bodies like circumstanced) is electrized positively; A, negatively. Or rather, B is electrized plus; A, minus. And we daily in our experiments electrize bodies plus or minus, as we think proper. To electrize plus or minus, no more needs to 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. Thus you may circulate it, as Mr. Watson has shown; you may also accumulate or subtract it, upon or from any body, as you connect that body with the rubber, or with the receiver, the communication with the common stock being cut off. We think that ingenious gentleman was deceived, when he imagined (in his Sequel), that the electrical fire came down the wire from the ceiling to the gun-barrel, thence to the sphere, and so electrized the machine and the man turning the wheel &c. We suppose it was driven off, and not brought on through that wire; and that the machine and man, &c, were electrized minus, that is, had less electrical fire in them than things in common.

Extract from: Faraday, Michael.  (1834) “On Electrical Decomposition.” Phil. Trans. 1834 124, 77-122

The theory which I believe to be a true expression of the facts of electrochemical decomposition, and which I have therefore detailed in a former series of these Researches, is so much at variance with those previously advanced that I find the greatest difficulty in stating results, as I think, correctly, whilst limited to the use of terms which are current with a certain accepted meaning.
To avoid, therefore, confusion and circumlocution, and for the sake of greater precision of expression than I can otherwise obtain, I have deliberately considered the subject with two friends, and with their assistance and concurrence in framing them, I purpose henceforward using certain other terms, which I will now define. The poles, as they are usually called, are only the doors or ways by which the electric current passes into and out of the decomposing body; and they of course, when in contact with that body, are the limits of its extent in the direction of the current. The term has been generally applied to the metal surfaces in contact with the decomposing substance; but whether philosophers generally would also apply it to the surfaces of air and water, against which I have effected electrochemical decomposition, is subject to doubt. In place of the term pole, I propose using that of electrode1, and I mean thereby that substance, or rather surface, whether of air, water, metal, or any other body, which bounds the extent of the decomposing matter in the direction of the electric current.

The surfaces at which, according to common phraseology, the electric current enters and leaves a decomposing body are most important places of action, and require to be distinguished apart from the poles, with which they are mostly, and the electrodes, with which they are always, in contact. (…) The anode2 is therefore that surface at which the electric current, according to our present expression, enters: it is the negative extremity of the decomposing body; is where oxygen, chlorine, acids, etc., are evolved; and is against or opposite the positive electrode. The cathode3 is that surface at which the current leaves the decomposing body, and is its positive extremity; the combustible bodies, metals, alkalies, and bases are evolved there, and it is in contact with the negative electrode.

I shall have occasion in these Researches, also, to class bodies together according to certain relations derived from their electrical actions; and wishing to express those relations without at the same time involving the expression of any hypothetical views, I intend using the following names and terms. Many bodies are decomposed directly by the electric current, their elements being set free; these I propose to call electrolytes4.
Finally, I require a term to express those bodies which can pass to the electrodes, or, as they are usually called, the poles. Substances are frequently spoken of as being electro-negative or electro-positive, according as they go under the supposed influence of a direct attraction to the positive or negative pole. But these terms are much too significant for the use to which I should have to put them; for, though the meanings are perhaps right, they are only hypothetical, and may be wrong; and then, through a very imperceptible, but still very dangerous, because continual, influence, they do great injury to science by contracting and limiting the habitual views of those engaged in pursuing it. I propose to distinguish such bodies by calling those anions5 which go to the anode of the decomposing body; and those passing to the cathodecations6; and when I have occasion to speak of these together, I shall call them ions. Thus, the chloride of lead is anelectrolyte, and when electrolyzed evolves the two ions, chlorine and lead, the former being an anion, and the latter a cation.

These terms, being once well defined, will, I hope, in their use enable me to avoid much periphrasis and ambiguity of expression. I do not mean to press them into service more frequently than will be required, for I am fully aware that names are one thing and science another. It will be well understood that I am giving no option respecting the nature of the electric current now, beyond what I have done on former occasions; and that though I speak of the current as proceeding from the parts which are positive to those which are negative, it is merely in accordance with the conventional, though in some degree tacit, agreement entered into by scientific men, that they may have a constant, certain, and definite means of referring to the direction of the forces of that current.