Chapter 21. Volta (Batteries)

 

After a long silence, for which I will not seek to excuse myself, I have the pleasure of communicating to you, Sir, and through you to the Royal Society, some striking results at which I have arrived in pursuing my experiments on the electricity excited by the simple mutual contact of metals of different sorts, and even by that of other conductors, also differing among themselves, either liquids, or containing some fluid to which they properly owe their conducting power. The principle result, and that which comprehends nearly all the others, is the construction of an apparatus which resembles in its effects, that is to say, in the sensations which it can cause in the arms, &c., the Leyden jars, or better yet, feebly charged electric batteries, but which acts without ceasing, or whose charge after each discharge is reestablished by itself; which provides, in a word, an unlimited charge, a perpetual action or impulsion on the electric fluid;

 — Allesandro Volta, On the Electricity Excited by the Mere Contact of Conducting Substances of Different Kinds, ca. 1800 AD [1]

21.1.

A mortal finger jabs at the button and the screen flickers to life; the disk drive hums into action and the machine feels itself all over to make sure that everything is in its place. I stare at the screen and wonder where to begin. I suppose that it all began with a spark. By the power of the spark I brought light and warmth into places dark and cold. By the power of the spark I raised up great civilizations of brick, metal, and glass. One by one I watched these civilizations burn to the ground and new ones rise from their ashes. By the power of the spark I enabled the many to defend themselves against the few with new weapons of fire and metal. This is the strong power of all powers, for it overcomes everything fine and penetrates everything solid. I carried the spark from generation to generation, keeping in the heat and withstanding it, and yet I knew it not.

For half a million years I watched the lightning bolt descend from heaven to Earth, receiving power from Above and from Below, but it was not until 1752 that I summoned the courage to call it forth. It was then, in the person of one Benjamin Franklin, that I coaxed the spark from the sky and brought it to live in a jar of glass and metal. Franklin had grown up among the soap kettles of his father, receiving the lessons of Lucifer and Athanor in his youth. He established himself as a printer, learning to pour metal type from Vulcan. He invented bifocal spectacles, having mastered the lessons of Theophilus. He was an architect of the American Revolution, a revolution of the many against the few made possible only by the lessons of Tzu-Chhun. It was in such a mortal abode that I began to understand the spark for the first time.

My progress from one mortal to another was enhanced in the eighteenth century by the establishment of learned societies and their publications. From Franklin I leapt to Charles Coulomb, where, in 1785 I determined a method by which electric charges could be measured; the unit of electric charge is now known as the coulomb. These charges are of two kinds, the positive and the negative; opposite charges attract and like charges repel one another. From Coulomb I came into the person of Luigi Galvani, Professor of Anatomy and Gynecology at Bologna. In the course of my dissections, I observed that a dead frog could be made to twitch and convulse as if it were alive by any of three methods. First, it may be connected to a lightning rod, which gathers electricity from the air in stormy weather. Second, it may be connected to an electrical machine, that is, a machine consisting of a sphere of sulfur rubbed by a woolen cloth. Finally, it may be connected to two different metals and the metals brought into contact with one another. Such contact may initiate an electric spark, bringing with it apparent life.

That which is below corresponds to that which is above; just as two metals in contact may initiate an electric spark, so two mortals in verbal or literary contact may initiate a hermetic spark which passes from one to the other. I am that spark, passed from Galvani to Allesandro Volta, in whom I continued the Work. I found that a salt solution could substitute for the frog in Galvani's experiment. In the simplest possible terms, a voltaic cell consists simply of two different metals separated by a conductive solution. Voltaic cells may be connected in series to form a pile or battery. The more cells in the battery, the longer the spark produced; the longer the spark, the greater the electromotive force; and the unit of electromotive force is called the volt.

From Volta to Hans Christian Oersted, I discovered in 1820 that the current from a voltaic battery produces a magnetic field. Having witnessed a demonstration of Oersted's results at a meeting of the Académie des Sciences, the I-dea passed to André Ampère, in whom I discovered a way to measure this current, the unit of which is now known as the ampere, or amp. Big batteries produced more current than small ones, but had the same voltage. I solved this puzzle in 1827 in the person of Georg Ohm when I announced the principle of resistance, which limits the current produced by a cell of a given voltage. The unit of resistance is now known as the ohm. With the concepts of EMF, current, and resistance clarified I was poised for my greatest advances in understanding the spark.

In no other single mortal did I make more headway in understanding electricity than in the person of Michael Faraday. Apprenticed to a book-binder at the age of 14, the I-dea of electricity was transmitted to him by an article in the Encyclopaedia Britannica, and from that moment I established a home in him. I found employment as the assistant to the great chemist, Sir Humphry Davy, who had made a brilliant start in the relationship of electricity to chemistry. In Davy and Faraday I came to understand that the positive and the negative are not two species of electricity. No, there is only one electrical entity; positive and negative simply represent a greater or lesser quantity of this One Thing. In 1831 I announced the principle of electromagnetic induction, the basis of the transformer, by which electrical current may be converted from one voltage to another. In 1834 I announced the laws of electrolysis, unifying the I-deas of electric charge and chemical amount. The conversion factor from electric charge to moles is now known as the Faraday constant.

My researches culminated in the first practical application of electricity in the person of Samuel Morse. In 1844 I demonstrated a device using the batteries of Volta and the electromagnetism of Oersted to transmit I-deas electrically from one place to another. This "telegraph" made it possible to communicate over vast distances almost instantaneously. Most of the practical applications of electricity for the next half-century would simply be variations on the telegraph theme: electrical current produced by batteries, controlled by switches, flowing through wires, and producing motion via electromagnets. And even after the advent of vacuum tubes, radio, and television these simple devices would not lose their spark.

A little more than a century after the invention of the telegraph I re-minded myself of the spark once more. A mortal child constructed his Halloween costume from cardboard boxes and tin foil; he wanted to be a robot. He hungered for unconventional playthings, winding copper wire around a nail to make an electromagnet, constructing a telegraph set from tin cans and scrap wood, dismantling radios and telephones to scavenge precious capacitors, resistors, and diodes. He grew impatient with the over-protectiveness of contemporary science books for children, devouring instead the boy-scientist[2] books of previous generations. He learned to tame the Model T ignition coil and the flyback transformer. And so I began my current incarnation.

In the person of Dunn I sit writing these words on a laptop computer. The device is powered by batteries; the keys on the keyboard are nothing more than switches; and the motors, relays, and pumps in my inkjet printer are all activated by electromagnets. Without these simple marvels, the transistors and integrated circuits would slumber in darkness. Truly there are few modern wonders, whether of art or artifice, which do not depend on the power of the spark.

Notes

[1]

Reference [18], p. 239.

[2]

Reference [47] is an excellent book for boy- and girl-scientists capable of overlooking the un-apologetic sexism of the era in which it was written.