Marvels of Modern Electronics
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Marvels of Modern Electronics

A Survey

Barry Lunt

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eBook - ePub

Marvels of Modern Electronics

A Survey

Barry Lunt

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About This Book

This scintillating survey of the major electronic discoveries of the past century — including static electricity, vacuum tubes, transistors, and television — focuses on the past forty years of technological innovation. Learn what's `under the hood` of computers, integrated circuits, the Internet, cell phones, GPS, optical fibers, space probes, and other modern wonders. Engaging and mildly technical, this authoritative treatment can be understood by anyone with a high school education and an interest in technology.
A brief history of electronics is succeeded by explorations of developments in electrical safety, radar, and deep-space probes. Additional topics include the operation of computers, data storage, and optical fiber communications as well as the electronics behind automobiles and consumer devices. The first four chapters provide background, and the following self-contained chapters may be read in any order. Author Barry M. Lunt, a Professor of Information Technology at Brigham Young University, also provides forecasts for upcoming directions in electronics.

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Information

Year
2013
ISBN
9780486320380
CHAPTER 1
ELECTRICITY: A RUDIMENTARY HISTORY
Static Electricity
The earliest record we have of electricity and its properties comes from the classical Greek civilization roughly around 600 B.C.E. They noticed that rubbing fur against a piece of amber (“elektron” in Greek) caused the amber to attract bits of dust, straw, or feathers. They did not come to learn a way to explain this behavior, nor did they create any useful products from the study of this phenomenon.
For approximately 2,000 years, this was about as much as we knew about what came to be called “electricity.” This particular form of electricity was termed static electricity; “static” means not changing or moving. Experimenters were able to build up a substantial charge of static electricity by rubbing various non-conductive materials against each other. They noticed that some materials behaved differently than others. For example, a piece of fur rubbed against amber would attract a piece of silk rubbed against glass, but two pieces of fur, each rubbed against amber, would repel each other.
Experimenters in the early 1600s created experimental devices using balls of sulfur, amber, and other materials. By rotating these materials against silk or fur, they were able to build up substantial charge, which could readily create a spark (or shock the experimenter!)
Having no other mental model readily available to understand this phenomenon, electricity was thought of as a fluid. Accordingly, in order to store this fluid, it was natural to think of storing it in a jar. Glass jars were readily available, but how to get one to hold this fluid? It was known that glass would not conduct this fluid, but that metals would. The answer was to put a lining of metal on the inside of the jar, and to connect this metal to the fluid. The electricity should then flow inside the jar and be retained there. However, when this was attempted, no electricity seemed to be stored in the jar. At the University of Leyden in the Netherlands (about 1746), the jar was also coated with metal on the outside. This device, later known as the Leyden jar, was capable of storing a substantial amount of this electric fluid, as evidenced by the sparks or shocks it could produce. Today we know that a Leyden jar was an early type of capacitor, a device which can hold small amounts of electric charge. A common application for a capacitor today is to hold the charge from a battery so it can be quickly released in a flash for a camera.
It should be appreciated that in these early days of experimentation, no devices were available to allow the experimenters to quantify their results and thereby be able to perform truly scientific experiments. One couldn’t measure the amount of static electricity being generated or stored in a Leyden jar, nor how energetic the spark was when the electricity was discharged. One could only say that a certain discharge was louder, or the spark was longer, or the shock received by the experimenter was greater. But such were the times, and such was the determination of the experimenters that this did not dissuade them from their studies.
A classic example of this is the kite-flying experiment of Benjamin Franklin. The question he sought to answer: Was lightning the same thing as this static electricity which people had been generating, storing, and studying? To answer this question, he equipped himself with the standard tools of the time, which included a Leyden jar, a kite, and a skeleton-type key, which he tied near the bottom end of the string. The thought was that, on a cloudy day when lightning was striking, the kite would pick up some of this “fluid;” it would travel down the string, through the key, and then into the Leyden jar. His kite flew, the key supplied sparks (which he felt by letting them discharge to his wrist), and he was able to store some of this fluid in a Leyden jar. His experiment was a great success, but he could easily have been killed (as a few others were who repeated his experiment)! He later proved that lightning was indeed the same as static electricity, by using the filled Leyden jar to perform experiments already familiar to himself and other electrical experimenters.
Many worked on the idea of producing some kind of useful work with this electricity. The steam engine was already in use in many applications, but it was large, slow, heavy, and potentially very dangerous. If an electric motor could be made, it would be of great use in many applications. Over the years, several types of static electricity motors were made, but they proved far too weak to perform useful work. Static electricity was just too ephemeral, and it was always a challenge to keep it from arcing to places it should not go.
In the end, even today there are relatively few practical products that use static electricity. Great sideshow equipment exists, such as Jacob’s ladders, plasma balls, Tesla coils, and Van de Graaff generators, but only the last has much in the way of practical uses, and then only in very specialized devices, such as particle accelerators. There is one type of home smoke detector that works using static electricity, and electrostatic precipitators have done much to help clean up smokestack emissions. Additionally, static electricity is used in photocopiers and sometimes in painting and coating. There are surely other niche applications of which the author is unaware, but compared to normal (or “dynamic”) electricity, they are much less common.
A New Kind of Electricity
In the early 1770s, Luigi Galvani was experimenting with the muscles of frogs. Using electrostatic generators or Leyden jars to store electricity, he would apply some of this electric fluid to the muscles and they would twitch. He wisely concluded that there were electrical signals at work in a frog’s body, causing the muscles to respond accordingly. Later work on human bodies gave similar results, which gave great insight into how the human body works.
On his workbench, there was a metal covering of brass. The dissecting instruments were made of steel. He noticed that, occasionally, there was a twitch of the muscles when he applied the cutting blade, leading him to conclude that there was an electrical charge on the blade. While many others accepted his theory, Alessandro Volta did not. Indeed, by further experimentation, Volta (about 1800) showed that dissimilar metals in a moist environment actually created electricity. Thus, it was the brass and steel, in the environment of the moist frog, that created the electricity. This was a keen insight, and proved very useful.
Volta went on to create several stacks (or “piles”) of these electrical sources, which we now know as batteries, and did a great deal of experimentation with them. Each of Volta’s cells were made of zinc and copper, separated by a space filled with a brine solution. By stacking them, he found he could create more electricity.
Again, lacking any volt meters (the Volt was later named after Volta) or measuring instruments of any kind, Volta was left to his own devices to determine how to conduct experiments with these batteries. Knowing that his body could sense electricity, it made sense to him to use it. Accordingly, his lab book records that he would touch various parts of his body with electrodes attached to different batteries. If the sensation was stronger with one battery than another, he would correctly conclude that the stronger sensation was due to more electricity. On one occasion, he recorded that when he touched a fresh wound with these electrodes, the sensation was particularly acute. It is amazing that in spite of years of experiments of this type, he did not die of electric shock!
The biggest difference between Volta’s “batteries” (a term coined by Benjamin Franklin; others called them “Voltaic piles”) and the electrostatic generators of the time was that the battery gave a constant current, rather than momentary discharges. It was thus the first practical source of electricity. Although these batteries did eventually discharge and could not be recharged, they were nevertheless much more practical than the electrostatic generators. Finally experimenters had a source of electricity that would remain constant for several hours or days, depending on their application. One of the first practical applications they would see was in the telegraph, starting in about 1850. Each telegraph transmitter/receiver required some source of electricity to operate. The simple opening and closing of an electric switch (the telegraph “key”) generated the dots and dashes of the Morse code; batteries were the only source of electricity which could supply this need.
And Yet Another Kind (of Electricity)!
For centuries, scientists were fascinated by the properties of magnetism. The manifestations of this phenomenon were only available from lodestone, a naturally occurring magnetic material found in many places around the earth. It was common for physics professors to use lodestone magnets and compasses to demonstrate various properties of this force. It was also common for physics professors, after the widespread availability of batteries, to demonstrate various properties of electricity. This often included showing how electricity could be conducted through wire.
During one of these demonstrations, the physicist Hans Christian Oersted was busy demonstrating the heating of iron wire as electricity from a battery passed through it. He noticed that each time he connected the battery to the wire, the nearby magnetic compass moved. He worked for months experimenting with this newly discovered phenomenon, keeping it a secret, but was unable to explain the results. Eventually, he chose to publish his findings without explanation.
Soon after Oersted published his findings, the field began to expand rapidly. Andre-Marie Ampere showed that two wires conducting electricity exerted a magnetic force on each other. The insightful and careful experimentalist Michael Faraday showed that not only did electricity flowing in a wire create magnetism, but the reverse was true: a magnet moving near a wire caused electricity to flow in the wire! Soon after, he produced the first electric motor and the first electric generator. When asked what good they were (the electric motor and generator), he replied, “What good is any newborn baby?” Indeed, his motor and generator were initially of very little interest, since there were no applications! But the eventual impact of these inventions was staggering; today well over 95% of all electricity generated uses the principles he demonstrated with his electric generator, and nearly 100% of all motors use the principles he demonstrated with his first electric motor. Even internal combustion engines, both gasoline and diesel, use electric motors as starter motors and use generators (commonly called alternators) to keep the batteries charged.
Figure 1-1:
A magnet moving near a wire (or any conductor) will produce a flow of electricity.
The invention of the electric generator and motor all occurred by about 1820. It would take several decades before the electrification of the United States was well underway (about 1890), but in localized applications, the electric generator began to supply energy to drive electric motors, which began to replace the steam engines common to the era. Today, in nearly all applications where electricity is available, electric motors provide the driving mechanical force. It is also true that if large quantities of electricity could be stored easily, automobiles would all be powered by electric motors, and the internal combustion engine would become a rarity.
And Yet Another (Type of Electricity)?
The end of the previous section leaves us with three kinds of electricity: static, battery-supplied, and generator-supplied. As has been mentioned, static electricity has historically been much less useful than the other two types, and this is still true today. But there is a fourth kind of electricity, a kind that doesn’t normally seem much like electricity at all to us.
In reality, all four of these kinds of electricity are one and the same, and differ only in how they are created and transmitted. The question of what electricity really is, which earnestly begs an answer, will have to wait until a subsequent section, just as it had to wait in history until after all four kinds of electricity were discovered and began to be exploited.
In 1864 a brilliant mathematician and physicist (ever notice how physicists are nearly always also great mathematicians?) named James Clerk Maxwell was working on this very interesting relationship between electricity and magnetism. Since its discovery over 40 years earlier by Oersted, this phenomenon had basically gone unexplained but had not gone unexploited. Maxwell’s breakthrough was to show mathematically how these two forces were interrelated, and in the process he showed that the speed of light was included in the relationship. This meant that these two forces, electricity and magnetism, were actually different manifestations of the same force, which we now call electromagnetism. It also meant that in a vacuum, these electromagnetic forces would travel at the speed of light. Maxwell also predicted that light itself would be discovered to be simply another manifestation of this same force. Although Maxwell’s predictions seemed incredible at the time, the subsequent years soon showed his conclusions to be correct.
Following on Maxwell’s work, another great experimenter named Heinrich Hertz was able to use a simple spark gap (like the spark plugs in an automobile engine) and some iron filings to show how the electromagnetic waves predicted by Maxwell indeed existed, and how they could be projected across a room and detected on the other side. This work was quickly followed by developments from Guglielmo Marconi, in which he extended the range of his ability to send and detect these very weak waves. Working in his lab, he successfully repeated Hertz’s experiments, then found ways to extend the distance beyond his lab, beyond the estate where he worked, and beyond the confines of what he could easily put together for his experiments. Eventually he found his way up from Italy to France, where he successfully transmitted and received Morse code across the English Channel. In December of 1901, he culminated this work by successfully transmitting and receiving the letter “s” in Morse code across the Atlantic Ocean, from Scotland to Newfoundland.
This transatlantic accomplishment deserves an important side note. Marconi knew very well that these “radio” waves he was working with were electromagnetic waves, and that they traveled only in straight lines. He also knew very well that the Earth was round. It made very little sense to expect that he could send these waves all the way from Scotland to Newfoundland, following the curvature of the Earth! But regardless of the impossibility of this feat, he succeeded! Today, we know he succeeded because of the ionosphere, an electromagnetically charged layer of the atmosphere off which his radio waves bounced back to Earth. But no one knew of such a layer in 1901!
The development of the radio (then called the “wireless”) helped solve the vexing problem of how to communicate with ships. Telegraph required the presence of a wire, over which the telegraphed signals traveled; obviously this would never work for ships. Marconi’s developments made ship-to-ship radios soon available, and it is due to the presence of one on board the Titanic in 1912 that there were any survivors at all of that infamous tragedy.
As with the development of the battery and the electric generator, it is difficult to overstate the importance of the development of radio. Countless are the devices we have available to us today which use this kind of electricity, and many are the applications yet envisioned.
So Just What IS Electricity?
From the earliest days of Greek experimentation with static electricity to the much more recent experiments of Hertz and Marconi, physicists had struggled to understand what electricity was. The idea of a fluid was the only metaphor they had readily available, and although there were many things explained through this metaphor, there were many other things about electricity that were not explained by it. How could it flow in solid wire and in empty space? How could it propagate at the speed of light? Why did some materials conduct electricity well, while others either conducted it very poorly or apparently not at all? How could one tell how much electricity was stored in a Leyden jar? How could one tell how much electricity a battery would deliver? Just what WAS electricity?
The answers to these questions would have to await the discovery of the electron and the atom, which began in the early 1900s. We are again indebted to the Greeks for the idea of the atom. The word “atom” was used by the Greek philosopher Democritus to describe the smallest possible piece of matter that could be created by dividing a lump of matter into successively smaller pieces.
The history of the atom, as fascinating as it is, is not central to this discussion, and so will be gently side-stepped. Suffice it to say that some of the greatest minds of the 20th century worked on this, and their names (such as Einstein, Bohr, Heisenberg, and many, many more) became very familiar. The results of their work are immeasurably valuable to us, as they give us a way to answer the questions posed in the first paragraph of this sec...

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