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Very closely related to the concept of electricity is the concept of magnetism. In this section, you will study how these two phenomena interact.
-What is a magnet?-
Magnetism has been known to humans for well over 2000 years. The ancient Greeks discovered a peculiar lead-colored stone that had the mysterious ability to attract small particles of iron ore. Some time later, the Chinese found a practical use for this seemingly magical stone. They learned that if a piece of this stone is suspended on a string or floated on a liquid it always tries to point in one specific direction (north). Because they used this device to lead them through the desert, the stone came to be called lodestone (that is, the leading stone).
You know now that the lodestone is a natural magnet. Although in some ways, magnetism is still rather mysterious, much is now known about its properties. Magic is not involved. You can make magnets out of certain other materials, even though they aren’t naturally magnetized. Lodestone is a fairly weak magnet, but stronger magnets can be made of iron, nickel, cobalt, or steel.
The two opposite ends of a magnet are called the poles. See Fig. 1. One pole will tend to point towards the earth’s north pole if the magnet is floated or freely suspended. This north-seeking pole is called the north pole of the magnet. The other pole is referred to as the south pole.[S N]
above: Fig. 1 Poles of a magnet.
Remember that in an electrical circuit, like charges repel and opposite charges attract. The same effect occurs with magnetic poles. If two magnets are brought together, north pole to north pole, they will try to repel each other. If, however, one of the magnets is turned around so that the north pole of one magnet is facing the south pole of the other, the magnets will exhibit a strong attraction towards each other.
If you place a bar-shaped magnet under a sheet of paper, sprinkle some iron filings on top of the paper, and shake the paper gently, the filings will tend to arrange themselves into a pattern like the one shown in Fig. 2.
Notice that the iron filings arrange themselves in a set of parallel lines arcing from one pole to the other. These lines never cross or unite. They are an indication of the magnetic lines of force, or flux. The area they cover is the magnetic field.
The flux flows from the north pole to the south pole of the magnet, just as electrical current flows from the negative terminal to the positive terminal of a volt age source. The flux is produced by a force called magnetomotive force. Magnetomotive force is somewhat analogous to electrical voltage (which is also sometimes called electromotive force).
Just as certain substances conduct electrical current better than others, certain substances allow magnetic lines of flux to pass through them more readily than other substances. In other words, some materials present a greater resistance to the flux. The magnetic equivalent of resistance is called reluctance.
The similarities between magnetism and electricity are so strong that Ohm’s law applies to magnets too. In magnetic circuits, flux equals magnetomotive force divided by reluctance. This relationship directly reflects the electrical formula, cur rent equals voltage divided by resistance (I = E/R).
--Producing magnetism with electricity--
When an electric current passes through a conductor, such as a piece of copper wire, a weak magnetic field is produced. The magnetic lines of force encircle the wire at right angles to the current flow, and are evenly spaced along the length of the conductor. See Fig. 3. The strength of the magnetic field decreases at greater distances from the conductor. The size and overall strength of the magnetic field is dependent on the amount of power flowing through the electrical circuit, but it’s always fairly weak. The magnetic force surrounding the conductor can, however, be dramatically increased by winding the wire into a coil, so the lines of force can inter act and reinforce each other.
An even greater magnetomotive force can be generated if the coil is wound around a piece of low reluctance material, such as soft iron. Because the magneto- motive force vanishes as soon as the current stops flowing in the wire, you have a magnet that can be turned on and off. The strength of the magnet is also electrically controllable. Such a device is called an electromagnet.
--Producing electricity with magnetism--
Because you can produce magnetism with an electrical current, it shouldn’t be surprising that you can also produce electricity with a magnet. Look at Fig. 4. It’s basically the same as Fig. 3, but there is no electrical voltage source, and the material in the center of the coil (the core) is a permanent magnet.
If you move the magnet up through the coil of wire, an electric current will start to flow through the wire. The strength of this induced current depends on a number of factors. These include the intensity of the magnetic field, how many lines of force are cut by the conductor, the number of conductors (each turn of the coil acts like a separate conductor in this case) cutting across the lines of force, the angle at which the lines are cut, and the speed of the relative motion between the magnet and the conductor.
This current will continue to flow until either the magnet is too far away for any of its lines of force to cut across the conductor, or the magnet stops moving.
If the magnet and the coil are stationary with respect to each other, no current is induced. Then, if you push the magnet back down through the coil (the direction of the movement is reversed) current will also flow, but it has the opposite polarity That is, it flows in the other direction. The exact same effect can be achieved if the magnet is stationary and the conductor is moved. It’s the relative motion between the components that is important.
All this might not seem terribly useful, because you have to keep moving the magnet or the coil back and forth to produce a continuing current. The current will keep reversing polarity each time the direction of movement is changed, but this method is actually a very efficient way of producing electricity.
This concept is used by power companies to produce their high-wattage ac power. Any of a number of mechanical means can be used to rotate a conductor between a magnetic north pole and south pole (see Fig. 5). It’s usually more practical to rotate the conductor rather than the magnet. Because the conductor is rotating between the magnetic poles, the direction of its relative movement between the poles appears to alternate, so the induced current, as mentioned above, is an alternating current. Very large amounts of electrical power can be produced in this manner.
-Health concerns and electromagnetic fields (EMF)-
We’re surrounded by EMF … if you’re out in the wilderness, you are not isolated from EMF. There is the natural background from planet Earth’s magnetic field (what makes your compass work) … and you may have GPS or iPhone that relies of EMF for its functionality. Is EMF safe for humans and animals? How much is considered okay? And long can a human tolerate higher-than-normal EMF without long-term impact to health and safety?
These are times of health and safety concerns. Almost every week, the news tells you of something new to worry about. Sometimes these reports are based on valid, even serious concerns. Other times they are based almost entirely on mistakes and misinterpretations, or even deliberate hoaxes. In almost all cases, the practical risk in the real world is greatly exaggerated in general news reports. There is a crying need for intelligent perspective in reporting ecology and health issues to the general public.
It’s no longer possible or reasonable to write an article, blog or even a topical book on technological theory without considering such issues. These issues are inescapable in modern society. You can’t afford to ignore them. Unfortunately, but inevitably, the concern forces the book a bit of a detour from the discussion of electronics theory. But the issues at hand are important enough to make such a detour worthwhile.
At the risk of going even further astray from the main subject of this book, it’s probably useful to first offer some general thoughts about such issues and how they are reported to and perceived by the general public. Then you can take a more informed look at the current concerns over the alleged health-related effects of electromagnetic fields, and other specific issues that relate to electronic technology.
--The problem of proof versus disproof--
It’s a sad fact that overall the reporting of scientific issues in the popular press (television, newspapers, general news magazines, etc.) has been deplorable. There are very few news reports on scientific issues that don’t suffer from major errors of fact. This is not to say such misstatements are due to deliberate or conscious bias. They are the results of poor (or non-existent) scientific training on the part of the reporters. Generally, a solid science background is not considered a requirement for science news reporting. More often than not, such assignments are made solely on journalistic qualifications. Often, any related technical experience or schooling (or lack thereof is considered irrelevant. But in today’s culture, scientific and technological issues are vitally important. How can they adequately be reported by someone who doesn’t really understand them? It’s like sending someone who has never heard of football out to cover the Super Bowl. No matter how good a journalist the person is, he or she will turn in a very distorted story, filled with errors and misinterpretations. The reporter won’t know which facts are important and need emphasis and which are more or less irrelevant.
Scientific and technological issues are often complex, and most professionals in this area don’t have very good communications skills. They can write reports that are understandable by their equally trained colleagues, but they all too often don’t really know how to break down the relevant information so it’s understood by the general public. So the scientifically untrained reporter interviews a scientist, and even though he or she doesn’t really understand the underlying theories and principles, the reporter must simplify and condense what the scientist said for the readers. But if the reporter doesn’t fully understand the key principles involved, how can he or she avoid introducing errors and misconceptions when simplifying or even rewording. Even using the scientist’s exact words might lead to misinformation if quotes are taken out of context.
For example, scientific caution often leads to public paranoia over undefined risks. When a scientist says, for instance, that there is no 100% safe level of radioactivity, that is not necessarily grounds for concern. It certainly doesn’t mean that all radioactivity is inherently bad. There is some scientific evidence that indicates that life would not be possible without some minimal amount of radioactivity. Even a level of zero would be unsafe in the sense the scientist means.
Radioactivity occurs when an atom emits subatomic particles and energy. When certain subatomic particles hit a chromosome, they can cause genetic damage. The more subatomic particles there are in a given area (that is, the higher the level of radioactivity), the better the odds that a particle will hit a chromosome and cause damage. As long as there is at least one subatomic particle, there is always some chance that it might make a lucky hit. The odds would be overwhelmingly against a hit under such circumstances but not impossible. A scientist would not say the situation was completely risk free, unless the chances of the negative event occurring are true zero, without rounding off. If there is 1 chance in 1,000,000,000,000, it still counts as a risk to the scientist, even though in practical terms, there is virtually no risk at all. So when the scientist says no level of radioactivity is completely safe, he just means the risk is never true zero, but the lay person interprets the statement as meaning that any radioactivity at all is actively dangerous.
Often the odds of being harmed by a technological risk that many people worry about are considerably poorer than the odds of being killed by a herd of stampeding zebras on Main Street. It could happen, but it’s not at all likely.
Another example is that some reports stated that scientists had not ruled out the possibility of AIDS being contracted by kissing. When scientists were asked if it was possible to catch AIDS by kissing, they replied that such a possibility had not being conclusively disproven, even though there was no scientific evidence to suggest it was possible. The odds were very strongly against such a connection, but the scientists didn’t want to claim to be all knowing. It’s always extremely difficult to conclusively prove that there is a true 0% chance of contracting any disease by any given means. It has not been conclusively proven that making funny faces in a mirror can’t cause AIDS, but there is no realistic reason to worry about making funny faces in the mirror. The specific connection has been neither proven nor disproven, and existing evidence suggests it’s an unlikely connection.
Just because something has not been conclusively disproven does not mean it has been proven. Similarly, just because something has not been conclusively proven does not mean it has been disproven. It seems that many, if not most lay people, and even some scientists and technical professionals with excellent academic credentials, have great difficulty making this critical distinction. It’s vital to understand this to assess any technological risk intelligently.
There is a critical difference between proof and evidence that is often ignored, even by professionals and experts. Inevitably this leads to foolish dogmatism and misinterpretation of facts. Proof is absolute and unquestionable. In the real-world, true scientific proof is very rare and perhaps even nonexistent. There is never any intelligent controversy over proof. Evidence, on the other hand, is subjective by definition. It requires interpretation. Two equally qualified experts might interpret the exact same piece of evidence in two very different, and perhaps even totally opposite, ways. To complicate matters further, they might not agree on just what is or isn’t valid, meaningful evidence for the question at hand. One expert’s “conclusive evidence” might be unconvincing, or even totally irrelevant to another expert with equal credentials.
Just because someone is an expert in a given field, does not mean he or she is automatically always right. An experiment that gives very impressive results, which might look like conclusive proof to the lay person (and some experts) might later be found (probably by other experts) to be seriously flawed in its procedures, per haps in a very subtle and unexpected way, so the results are not truly meaningful at all. There is a tendency to say “such-and-such an experiment (or series of experiments) proves this-and-that conclusion.” In almost all cases it would be more accurate to say that “such-and-such an experiment (or series of experiments) indicates this-and-that conclusion.”
lay people must always bear in mind that all experts in every field are human beings too, with the same sorts of failings, unconscious biases, and blind spots as the rest of humanity. Every expert is wrong in his field of expertise at least some of the time.
Any time there is a controversy on any scientific issue, it means that the experts are in disagreement over the interpretation of the available evidence. For every expert who says yes, there is another expert with equally impressive credentials who says no. If the issue had been proven, there could be no scientific controversy.
Curiously, and perhaps surprisingly, the lay person is more likely to be exposed to the radical, minority viewpoint in scientific controversies. An interested, intelligent lay person might even find it difficult to find nonprofessional materials presented the majority viewpoint. This is because a radical, sensationalist theory will sell a lot more books at the newsstand, and a book covering a conservative, traditional theory will appear dry and dull to the lay person, who will probably leave it on the racks. So the conservative, mainstream scientific viewpoint is not as potentially profitable to publishers, so such general-level books are less frequently written and published. The mainstream scientific viewpoint is usually covered in some detail in the technical and professional journals for the field in question. Such publications might be hard for the general public to get hold of, or to understand them once found. But the wild, minority theories are covered in the news, in general magazines, and in popular books. The wilder and the more sensational the theory, the better it will sell to the general public. A viewpoint with little scientific support might appear to be scientific truth to the general public.
Notice that such theories are not automatically wrong. The mainstream scientific community has been dead wrong many times in the past and will similarly err many times in the future. The point is, such sensationalist theories should not be accepted as gospel. The more media hoopla there is over any scientific idea, the more controversial it must be, and the more strongly it goes against mainstream scientific thinking.
It’s rarely, if ever, valid or reasonable to conclude that the experts who oppose the sensationalist theory have a vested interest, or in the pay of those who do. In fact, such a conclusion is almost always a sure sign of paranoid thinking. If there wasn’t good scientific reason doubt the new theory, there would be no real controversy over it. The theory might ultimately turn out to be completely true, but as long as the controversy exists, there is room for doubt, and it’s unscientific and even foolish to insist “such-and-such is absolutely true” or “such-and-such is absolutely false” while the controversy continues, indicating that not all qualified individuals have drawn the same conclusions from the inevitably subjective and incomplete evidence.
Often the new, controversial theory ultimately turns out to be only partially true. For example there might be some risk involved with “such-and-such,” but not nearly as much as was claimed in the sensationalist literature.
Many authors, even those with strong academic credentials in the field will write a sensationalist book more for monetary than scientific reasons. They might (perhaps not completely consciously) exaggerate the case to sell more books. Read any scientific literature oriented toward the general public cautiously, and never let any one author fully convince you on the issue. (Yes, that includes the author of this article.)
Often the title will give you a clue about the author’s intent in writing the book. For example, one book on the subject of the alleged health risks of electromagnetic fields, which you will read about, has the lurid, sensational and alarmist title Currents Of Death. Such a wild, almost paranoid title should raise some doubt in the intelligent reader. To be fair, sometimes publishers change the author’s title to help the book sell more copies, so check out the text before drawing conclusions. If a book has a wild title but cautious, well-reasoned arguments in the text, the title probably wasn’t the author’s. But often, the text will be just as wild-eyed and paranoid as the title. Take such an author’s arguments with a grain of salt. The author might be sincere, but is lacking in perspective on the issue. Many fully qualified experts have an axe to grind that might get in the way of their scientific judgment.
Just because an author has a string of degrees, it does not mean he or she is automatically correct in his or her conclusions. In the book, the author might slant the evidence to support conclusions and ignore or misrepresent conflicting evidence. This might not be deliberate bias or fraudulent intent. Strong personal beliefs as a human being might be clouding his or her judgment.
--Do electromagnetic fields affect human health?--
The long detour before discussion of the specifics of the current electromagnetic field controversy is for a reason. Virtually all of the published information on this subject has been from the minority viewpoint that there are serious health risks to the general public from artificially generated electromagnetic fields. The main stream scientific viewpoint is that there is little or no real risk to the general public from artificial electromagnetic fields. That does not necessarily mean that the minority viewpoint is wrong. They might be right, or they might be partially right. The problem is that the lay public is being given the false impression that the minority viewpoint is the mainstream, majority conclusion of all “honest” experts. This idea is simply not true.
This issue is discussed as honestly and fairly as the author can in the limited space available. Personal opinions don’t intentionally color the presentation of the evidence. In fairness to you, the author’s opinions will be revealed before you complete the subject. No one is obligated to share the author’s viewpoint. It’s presented only so that you can compensate for any unintended bias in the discussion of the controversy.
--Natural electromagnetic fields--
First, be aware that you are always surrounded by electromagnetic fields. They occur naturally, and there is some fairly strong scientific evidence that if natural electromagnetic fields did not exist, life itself could not be sustained. In many respects, the Earth itself is a giant magnet. An reasonable discussion of the health aspects of electromagnetic fields must begin with an understanding of the natural electromagnetic background you are all continuously exposed to.
Because electromagnetic fields are completely natural phenomena, any risks associated with them must be of quantity, not of kind. Despite some of the more paranoid and sensationalistic of some of the writings on this subject, electromagnetic fields are not inherently harmful or bad.
All electromagnetic fields are, by definition, force fields. That is, they carry energy, and can produce an action at a distance. For example, a permanent magnet can move a small metallic object some distance away. The farther from the source, the weaker the electromagnetic field gets. The field strength drops off rather quickly, following a logarithmic, rather than a linear pattern.
It’s also important to realize that there are two basic types of radiation. Not all radiation is harmful. For example, ordinary light and heat are both types of radiation. Some forms of radiation are ionizing, and others are non-ionizing. Ionizing energy, such as X rays, are known to be biologically harmful and can cause a direct chemical reaction (ionization). Traditionally, non-ionizing radiation was considered to be mostly or entirely harmless. This is the cornerstone over the current controversy over the alleged health effects of electromagnetic fields, which are non- ionizing. If they have any effect, it’s apparently indirect, and it’s certainly less than that of ionizing radiation. If non-ionizing radiation was more potentially harmful than ionizing radiations, its effects would been discovered earlier, or at least at about the same time. The effects of ionizing radiation have been known for some time. The effects of non-ionizing radiation are still unclear and scientifically questionable.
In a sense, the planet Earth is a gigantic bar magnet, as shown in Fig. 6. The north and south poles of magnets are named for their electromagnetic similarity to the Earth’s North Pole and South Pole. The true magnetic poles of the Earth are not entirely stationary. They move around slightly, and are usually not located precisely at the true geographic poles.
Fig. 6 The Earth functions like a giant bar magnet. North pole -- South pole
There is some scientific evidence that from time to time in the past, the electro magnetic field of the Earth has reversed polarity. That is, the North magnetic pole became the South magnetic pole, and vice versa. Some scientists hypothesize that such large-scale magnetic field reversals were responsible for the periodic mass deaths of species that have mysteriously occurred in the Earth’s past. This theory is quite intriguing, but it’s very, controversial, and must not be accepted as proven fact. Many, perhaps most scientists today don’t believe any such magnetic pole reversals have ever occurred, or even that they could occur. The existing evidence, although somewhat impressive, is still highly questionable.
Many (not all) authors who believe in the harmful effects of electromagnetic fields tend to accept such controversial theories as given facts. This acceptance places their hypotheses on shaky ground right from the start.
The core of the Earth is molten rock, very heavy in iron. The spinning core of the Earth creates a dipole magnetic field with a magnetic north pole and south pole. As with any permanent magnet, force lines extend from pole to pole, as shown in Fig. 6. This illustration is not accurate, however. It shows what the magnetic fields of the Earth would look like if it was alone in the universe. But the Earth is far from the only electromagnetic object in the universe. It’s electromagnetic fields are inevitably acted upon by other cosmic objects. The primary influence is the Sun, because it’s so large and relatively close. For your purposes, you can assume that only the electromagnetic interference from the Sun is of significance. The effects from other planets, the moon, and nearby stars are real, but far weaker and more subtle than the effects from the Sun. They don’t change the overall picture significantly.
The Sun constantly emits a force known as the solar wind. Now, this is not a true wind, in the way you normally think of it here on Earth. An ordinary wind is a movement in air, and there is no air in space. The solar wind is a flow of high-energy atomic particles emitted from the surface of the Sun. In many respects, a solar wind acts rather like an ordinary Earth wind, so the name is appropriate, as long as you don’t take it too literally.
The solar wind contains particles with very high energy and moving at high speeds. Some of these high energy particles are of the ionizing type, but others are non-ionizing. There is still plenty of energy left in the solar wind by the time the particles travel the distance from the Sun to the Earth. The solar wind therefore interacts with the Earth’s natural electromagnetic fields. On the side facing the Sun, the solar wind particles push against the Earth’s magnetic fields, compressing them. Meanwhile, the fields on the far side of the planet are “blown” outward by the solar wind to form a long magnetotail. These effects are shown in Fig. 7.
The collision of the solar wind particles with the Earth’s magnetic fields creates a bow shock region in which these forces interact. Two special areas within this bow shock region are known as the Van Allen belts. Some of the solar wind high-energy particles are trapped within these belts, where they constantly spiral between the north and south ends of the ducts, as shown in Fig. 8.
The magnetosphere (the distorted magnetic fields surrounding the Earth) shields the planet from much of the Sun’s radiation, especially the potentially harmful ionizing rays. If the magnetosphere was destroyed or removed, all life on Earth would cease to exist. Spaceflights beyond the Earth’s magnetosphere must be of limited duration to prevent harmful effects to the astronauts exposed to the Sun’s powerful radiation without this natural shield. (Theoretically, an artificial magnetic shield could be designed and incorporated into future spacecraft, but such technology does not yet exist.) Such space flight missions beyond the Earth’s magneto sphere must also be timed carefully so they occur during quiet periods in the Earth’s cycle. During a solar storm, the ionizing radiation emitted from the Sun is much greater.
The Earth rotates within the magnetosphere, which remains stationary. The magnetosphere itself does not rotate. The same side always faces the Sun. As the Earth rotates under the magnetosphere, a given spot on the planet’s surface will experience a daily pattern of up and down fluctuations in the strength of the natural electromagnetic field. At certain times of day, the electromagnetic field is stronger, and at other times it’s weaker. Some scientists believe these electromagnetic level fluctuations might help explain the daily biological rhythms that occur in many species. For example, people who are placed in caves or enclosed buildings for ex tended periods with no way to tell time will still tend to synchronize their sleep- waking patterns with the Earth’s night-day cycle, at least, approximately. Actually, there seems to be a tendency to act as if the day was a little shorter than the Earth’s actual 24 rotation speed.
This theory has a lot to recommend it. However, before ascribing too much importance to this still controversial theory, remind yourself that there are almost certainly other physical phenomena that has a daily fluctuation pattern synchronized to the Earth’s rotation. The fluctuations in the natural electromagnetic field might have nothing at all to do with biological rhythms, despite the suggestive evidence. It seems like that they do have at least some effect, but this is far from proven to date.
-- Magnetic storms --
In the Earth’s upper atmosphere, the interaction between the solar wind particles and the magnetosphere generates very large electrical currents, often with power levels in the billions of watts range. This level is much larger than virtually all electrical sources created by humans. This natural atmospheric electricity creates ionizing radiation and a number of electromagnetic waves in the ELF (extra-low frequency) and the VLF (very-low frequency) range. The VLF range runs from 100 to 1000 Hz, and the ELF range covers everything from 100 Hz on down to 0 Hz (dc). These effects are all normal in a quiet field resulting from a steady flow of solar wind.
Obviously, because all life on Earth is exposed to these effects, they can not be considered inherently harmful, at least, not at their naturally occurring levels. You must keep in mind that the upper atmospheric layers shield much of this energy from reaching the surface of the Earth itself. Much of the shielding is per formed by the natural ozone layer, which is why detected holes in the ozone layer are worrisome.
The picture is complicated by the fact that the Sun is not at all a steady energy source. Solar activity rises and falls over an eleven year sunspot cycle. During periods of high solar activity, solar storms occur with some frequency. These so- called solar storms result from solar flares, or huge energy eruptions on the surface of the Sun. Some solar flares can shoot up hundreds of miles above the surface of the Sun. The high energy of a solar flare increases the number of high-energy particles emit ted from the Sun. In effect, you have a higher gust of solar wind. There are more X rays, proton streams, and electromagnetic waves in the RF (radio-frequency) region hitting the Earth’s magnetosphere. Not surprisingly, these high energy bursts of solar wind can cause significant magnetic field disturbances in the Earth’s vicinity Such disturbances are called magnetic storms. They are not necessarily associated with meteorological storms (rain, thunderstorms, wind storms, etc.). Unlike Earth bound meteorological storms, which are usually geographically localized, magnetic storms often affect much of the Earth’s surface area at the same time.
During a magnetic storm, the strength of the Earth’s electromagnetic field fluctuates wildly, exhibiting great increases in strength. In some magnetic storms, these disturbances can induce very high power currents in electric power transmission lines and telephone lines. This induced power can sometimes cause a break down of the system. At the same time, similar disturbances in the ionosphere can cause significant interference or even complete breakdown in radio and television signals. These effects are relatively uncommon, but they are not rare or unusual in scientific terms. Again, such magnetic storms are a purely natural phenomenon, even though you notice their effects mostly in the disruption of communications and power systems.
There is some (mostly statistical) evidence that animal and possibly even human behavior patterns might be affected during a magnetic storm. Such a connection is highly controversial, however, and far from proven to the satisfaction of most scientists today. Even among those who are convinced of such effects, there seems to be considerable disagreement over just what the effects are—that is, what changes supposedly appear in animal or human behavior. It’s inherently difficult to scientifically study such effects (if any), because magnetic storms are not frequent, and they are usually of rather brief duration. It’s also difficult to predict just when such natural magnetic disturbances will occur.
--Electromagnetic fields created by humans--
In the modern, technological world, there are many artificial sources of electromagnetic fields. Any radio or television transmitter is, by definition, a high-frequency electromagnetic field generator. The broadcast signal being transmitted is nothing but a modulated electromagnetic wave. Few scientists today believe that these signals are potentially harmful, unless, perhaps, you are very close to a very powerful transmitter. Even then, inherent risks seem rather doubtful. The largest risk close to a radio or television transmitter antenna is the large ac power levels themselves. If you accidentally complete a circuit to ground, you could suffer a serious electrical shock or perhaps even electrocution. There isn’t much controversy there.
The present controversy over the alleged health effects of electromagnetic fields concerns primarily low-frequency fields, generally in the ELF (0 Hz to 100 Hz) range. Through most of the world, ac power plants generate ELF signals with a frequency of either 50 Hz or 60 Hz. As it happens, these particular frequencies don’t naturally occur to any appreciable degree in the normal electromagnetic spec- u-urn of the Earth, although they might briefly show up during a magnetic storm.
There are a lot of ac power plants operating in the world today to meet society’s increasing energy demands. In the course of the last half century or so, the electro magnetic fields created by humans have more than duplicated the hypothetical changes in strength and frequency that are assumed to have been responsible to past species die outs. Although this fact has been used to fuel paranoia and sensationalism on the electromagnetic field issue, it actually does not indicate a cause for major concern at all. Instead, it seems to call the worrisome theories into serious question. If you have already artificially exceeded the electromagnetic levels that supposedly caused mass species die outs, why haven’t there been widespread bio logical disasters? There have been a lot of species extinctions in recent times. Some have been entirely natural (species became extinct long before mankind and its technology came along), but most can be directly explained by other human causes— mainly pollution, hunting, and destruction of natural habitats. There haven’t been any mysterious extinctions that can be reasonably attributed to electromagnetic field disruptions caused by modern technology
These man-made electromagnetic fields have been around for decades and have covered most of the globe. Any health effects therefore must be very subtle in nature, otherwise there would be no room for controversy. This supposition does not mean that all concern over health effects of electromagnetic fields is trivial and inappropriate, but it does indicate a need to keep perspective. Subtle health effects can be cumulatively important, and could conceivably lead to disastrous effects in the future. But lurid sensationalism such as Currents of Death is unquestionably un scientific and irresponsible. The more extreme claims being made in this controversy have more to do with superstitious paranoia and technophobia than science. The ridiculous claims made by some paranoids could ultimately worsen the problem if it exists. If there is a subtle health risk from man-made electromagnetic fields, the extreme claims are so ridiculous that the mainstream of science is likely to dismiss the entire question altogether as unworthy of investigation. The legitimate grounds for concern gets covered up and masked by the nonsense, so the necessary re search is delayed, if not put off altogether.
Those with serious, scientifically valid concerns about the potential health effects of electromagnetic fields should speak out the loudest against the sensationalist nonsense spewed out by the paranoid extremists, which can only hurt the overall cause in the long run. The extremists discredit the entire question, which is generally the case in almost all such controversies.
--Electromagnetism and biology--
Electromagnetic phenomena have been known since ancient times. The mysterious and amazing ability of a magnet to act upon other objects with no direct physical connection between them has stimulated the human imagination. Until relatively recently, only natural magnetism and static electricity were familiar. But in the last couple of centuries, electricity has gone from a curiosity to an all-persuasive fact of life.
The link between electricity and magnetism was discovered early. Another early discovery was the presence of electrical currents within living things. For example, nerve impulses are both chemical and electrical in nature. Because electricity and magnetism seemed so magical to begin with, and there was definitely some biological connection, many fanciful theories and devices were created in massive quantities, especially in the 19th century. Hundreds of electrical or magnetic cures were touted for almost every imaginable ailment from broken bones to arthritis to general fatigue and listlessness. Some of these electromagnetic cures were concocted by sincere scientists with an incomplete understanding of the phenomena involved, but many were the work of out and out quacks and con artists. None of them were accepted by mainstream medicine because none of them worked. In fact, many of the so-called electrical cures were actually quite dangerous, subjecting the patient to potentially severe shock risks.
Perhaps the most “successful” electrical cure was shock therapy used for mental patients. A controlled electrical shock could calm down a violent or seriously disturbed patient. It also rattled their brains, damaged memories, and often affected normal nerve functioning. This rather barbaric treatment enjoyed quite a startling popularity in mainstream medicine for a while, but is now almost universally rejected as far more harmful than helpful. In fact, it’s doubtful that it ever did much more good than simply hitting the troublesome patient in the head.
When hypnotism was first discovered, it was often called animal magnetism. It was imagined that some sort of mysterious electromagnetic rays were transmitted from the hypnotist to the subject. Of course, there were never any such rays. Neither electricity nor magnetism have anything at all to do with the altered state of consciousness known as hypnotism. In fact, self-hypnosis demonstrates that a separate hypnotist is not required at all (although a hypnotist can be helpful in guiding the session). There is good reason to suspect that all hypnosis is actually self-hypnosis, even when there is a separate hypnotist offering suggestions to the hypnotized subject. The subject is never really under the hypnotist’s control. Hypnotized subjects can and do reject hypnotic suggestions that go against their moral code and values.
The ultimate electromagnetic “cure” was suggested in Mary Shelley’s famous novel, Frankenstein. In this novel, Dr. Frankenstein revived a reassembled corpse by applying electricity from captured lightening. Shelley probably got the idea from experiments that showed dismembered frog legs would jerk if an electrical voltage was applied to them. Of course, the voltage was simply stimulating the electrochemical nerve endings in the frog legs. They were completely dead, and the applied electricity made no difference in that fact, despite the resulting lifelike movement. Such experiments have no more to do with regenerating life by electrical means than using electricity to cause a motor to move. It’s just a natural electromechanical phenomena.
Electromagnetic cures are still advertised from time to time, but to date there is no solid evidence at all that any such gadgetry works, or is even based on scientific principles.
Of course, electricity can have definite harmful biological effects. The effects are especially present in high power (large current capacity) ac voltages. Low-power electrical shocks can cause some of the body’s nerve synapses to fire or to lock up, more or less randomly. The shock can cause bodily jerks, and temporary paralysis. A shock victim might be unable to control muscles sufficiently to let go of the hot wire giving the shock.
The uncontrollable physical jerks can lead to falling or hitting things, or other potentially dangerous accidents. If the applied current is increased, seizures, heart failure or other serious medical conditions could be caused. An electrical shock of enough force can be fatal.
Of course, electricity and magnetism are not the same thing, although they are closely related. Biological processes do utilize tiny electrical currents, though there doesn’t appear to be any way to positively stimulate biological processes by applying external electrical currents. But what of magnetism?
Here the biological connection is even more tentative and vague. It’s true that all living things are surrounded by a magnetic field extending out into space. Theoretically it would seem that living organisms possibly could be influenced by external electromagnetic fields. After all, there would have to be a physical interaction of the external electromagnetic fields and the dc electrical currents flowing through the organisms. But in practical terms, the magnetic field strength would almost certainly have to be extremely large to make much difference. Any external electro magnetic field would have to be stronger than the Earth’s natural electromagnetic field to counteract its natural effects (if any). If a compass works well in the vicinity, the primary magnetic field in the area must be the Earth’s natural magnetic field, so it’s doubtful that any other localized electromagnetic field is having a very significant influence. The natural force field is stronger, so it must be the primary controlling force.
Of course, some artificial electromagnetic field sources are strong enough to cause a compass to malfunction and give an incorrect reading. If there are any bio logical effects from external electromagnetic fields, they would occur almost exclusively under such conditions. A compass is surely more sensitive to magnetic fields than any biological organism.
There is some controversial evidence that some biological organisms might sense and respond to relatively minor fluctuations in the electromagnetic field of the Earth. But all of the existing evidence indicates that such effects are very minor and secondary. No known living thing responds to magnetism as a primary sense.
Biological rhythms or cycles have been well established since the 1960s. Many living things follow daily and annual patterns in certain ways. The sleep-waking cycle is an obvious example. Some creatures are diurnal—that is, they sleep at night and are active during the day. Other creatures are nocturnal, sleeping during the day, and becoming active at night. They will more or less maintain these daily patterns, even if ordinary sense clues are made unavailable. For example, in a cave or an enclosed room, the creature can not see if the Sun is up or not. So how do they know when it’s night and when it’s day?
These biological cycles are still largely a mystery. Anyone who claims to definitely know exactly how they work is a fool or a charlatan. A number of hypotheses have been suggested. One popular hypothetical explanation is that the creatures in some way sense the fluctuations in the Earth’s magnetic field and adjust the timing of their biological cycles accordingly.
Notice that even if this hypothesis is correct, the magnetic influence still must be a subtle one. If a dozen subjects are studied under the same conditions (including the same exposure to the same magnetic fields), their biological cycles won’t be perfectly synchronized. In some cases they might be significantly out of phase with one another. This means something else must be playing a part in the equation.
Some experiments have indicated more or less consistent response to con trolled magnetic field changes in some biological organisms. The most successful of these experiments have been with very, simple organisms, such as bacteria. It’s much, more difficult to establish a definite magnetic response in more complex biological organisms.
The most intriguing experiments along these lines with developed creatures have been some studies of homing pigeons that suggest the birds might use magnetic cues as a secondary, back-up method of finding their way home. Of course, the more obvious senses are far more important. There is no question that homing pigeons use visual cues whenever they can. But when the pigeons are fitted with special contact lenses that make it impossible to navigate visually, they can still find their way home, If a pigeon is fitted with the contact lenses and a small permanent magnet, they often seem to get confused or even lost. This result suggests they are somehow using magnetic cues which are blocked by the magnet they are carrying. On the other hand, if a pigeon is not visually impaired, attaching a permanent mag net to it doesn’t seem to make much difference in its ability to find its way home. The magnetic cues are obviously secondary in the pigeons’ navigation processes.
Dr. Robin Baker of the University of Manchester in England has conducted some controversial experiments suggesting that even humans have an innate ability to sense the direction of magnetic north. Placing a bar magnet against a subject’s forehead for about 15 minutes can disrupt this magnetic sense for as long as two hours after the magnet is removed. These results are far from universally accepted in the scientific community. Most scientists doubt that any such magnetic sense exists in humans. After all, if such a sense existed to any particular degree, why were such direction finding devices as the compass and the sextant ever invented? Human beings can get lost too easily to make an ability to sense magnetic north a very likely suggestion. It’s not just a matter of modern artificial electromagnetic fields confusing a natural magnetic sense. People were getting lost long before they started using electricity.
Once again, there might be something to Baker’s proposed magnetic sense, but it’s obviously a very weak, secondary sense that is normally almost completely unused by humans. (It would probably be reasonable to delete the word almost from that last sentence, but there is always some room for doubt.)
Until fairly recently, it was assumed that any biological effects from artificial electromagnetic fields were theoretically impossible. Modern science has indicated there is a real possibility of some subtle effects. Notice that these effects are not proven, they are just theoretically possible. This implies a need for further research, not for fear or paranoid concern. Any such effects must logically be quite subtle and secondary.
Most of the current links between health problems and artificial electromagnetic fields have been statistical. This means there is considerable room for error.
There might be some unaccounted for factors. The apparent statistical link might be coincidental, or the result of a common cause. For example, assume say condition A appears to be statistically linked with condition B. Does this mean condition B causes condition A? Possibly, but not necessarily. There might be an unaccounted condition C that causes both condition A and condition B. Or condition C might simply cause condition A, and condition B is simply an unrelated red herring. Statistical links can be useful scientific tools, but they never make up adequate scientific proof by themselves. There is always some built-in margin of error in any set of statistics. Real life always has too many variables to permit simple, unambiguous statistical links.
There have been a number of cases of workers employed around strong electro magnetic field sources having problems—usually just a vague feeling of being slightly ill, or abnormally tired. A few statistical studies of populations living near power plants or other large artificial ELF sources have greater incidence of certain psychological or medical effects. However, these studies have been far from conclusive. Different studies as often as not indicate entirely different effects under apparently similar conditions. You must also remember that any power plant or other large-scale ELF source will almost certainly be putting out larger than normal pollution and heating levels, adding more variables to the cause-and-effect question. Such statistical studies are suggestive, but they are not valid scientific proof themselves.
High frequency electromagnetic signals, especially microwaves, have been demonstrated to cause unnatural heating or feverlike effects under some conditions. Such high-frequency signals can also cause chromosomal damage under some conditions, especially in ionizing radiation is involved. This happens because the chromosomes or other cellular level components can physically resonate with the wavelength of the high frequency signal. Such resonance effects could not occur with ELF (extra- low frequency) fields, of course. The wavelengths are far, too long. This fact does not automatically rule out any biological effect from ELF fields—only direct resonance effects.
It’s true that ELF fields are effectively stronger than comparable high frequency fields. That is, a ELF wave of a given wattage will tend to travel further than a high frequency signal of the same wattage.
ELF fields are more penetrating than higher frequency fields. An ordinary RF signal can be blocked by the ground or the ocean, so regular radio won’t work in a submarine. But signals can be transmitted too and from a submerged submarine if an ELF carrier frequency is used. Because the higher the frequency of an electro magnetic field the more easily it’s blocked, it’s logical to assume that ELF signals can get places that higher-frequency signals will never reach. Does this make a difference biologically? Possibly, but it has not been scientifically proven as yet.
Some experiments have indicated that prolonged exposure to strong ELF fields might (but not always) lead to an increase in certain bio-chemicals in the body. These biochemicals are normally associated with stress. If this connection is true, it implies that strong ELF fields could, under some conditions, cause stress responses. Of course, a great many different things can cause stress in humans. There is no reason to assume that ELF fields would be inherently any worse than other stress stimulator.
ELF fields have been experimentally linked to cancer, but then, what hasn’t been? If everything that supposedly causes cancer really did, it’s truly remarkable that the entire human race didn’t die out years ago.
There have been other experiments with rats that indicated prolonged expo sure to strong ELF fields might be related to increased learning difficulties, and genetic damage. There might also be some effect on fetal development. These experimental results are all still controversial. It’s also worthwhile to remember that virtu ally all such experiments involve subjecting the subject rats to much stronger ELF fields than the average human being is likely to encounter. Once again, you have some cause for concern and further research, but there are hardly any reasonable grounds for paranoia or fear of a massive epidemic.
--ELF fields in the average home--
The strength of the Earth’s natural magnetic field at any given location typically has an average value of about 0.5 gauss. (Gauss is measure of magnetic flux density.) The daily fluctuation is only about 0.1 gauss. This is a seemingly small level. A small permanent magnet like the one that holds your refrigerator door closed is typically about 200 gauss. Such facts are used by sensationalist authors to stir up inappropriate fear. It sounds like an impressive difference between the Earth’s natural magnetic field and the refrigerator door magnet. But the magnetic field surrounding the permanent magnet drops off very rapidly with distance. The 0.5 gauss aver age value for the Earth’s magnetic field already takes these drop off factors into ac count. The actual magnetic field emitted by the Earth is much larger than this. A few inches away from the refrigerator door magnet, its magnetic field will be negligible in comparison with the Earth’s natural magnetic field. You can easily prove this yourself. Get a small compass. If you place it right next to the magnet, it will give an incorrect reading for north. Move a few inches away, and the compass will start working normally.
This apparently dramatic comparison—0.5 gauss to 200 gauss is misleading and even a little dishonest, because the 0.5 gauss value for the Earth’s magnetic field is distance compensated, and the 200 gauss rating for the magnet is not. Such logical errors apply to many, if not most, of the claims for electromagnetic health risks from household appliances.
At least one author claims that some devices, such as electrical blankets exhibit significant electromagnetic fields, even when the switch is off. This is not only incorrect, it’s absolutely ridiculous. When the switch is off, there is no current flow, which means there is nothing to generate any electromagnetic field at all. If the author in question measured such fields, as claimed in the book, they obviously came from some other source. Such silly arguments should be ignored.
Some electromagnetic alarmists express concern over the electromagnetic fields surrounding such lower power devices as electric clocks. Again, this concern doesn’t hold up to common sense. The electric clock on my desk is rated for 2.5 W. About half of this input power is used by a small lamp to illuminate the clock face. The remaining power must overcome the physical inertia and friction of the motor. In any electrical circuit most of the unused power is wasted as heat dissipation. Sure, the coils in the motor are surrounding by electromagnetic fields, as explained elsewhere in this guide. But these fields are quite weak unless very close. The self- induction effects of a coil (see section 8) normally occur over distances of just a tiny fraction of an inch. If there is too much spacing between the coil loops, it won’t work. In conducting some informal experiments, it appears that at a distance of about two feet, the gauss meter couldn’t detect the presence of an electric clock at all. To be worried about the electromagnetic fields surrounding an electric clock is pure superstitious paranoia.
The most serious concern of electromagnetic radiation in the average home would be in a television set. Virtually all the energy radiated from any television set is in the form of simple light (from the picture tube) and heat. Old tube television receivers sometimes generated fairly large amounts of X rays, which could possibly be harmful. Extensive shielding was legally required. These legal requirements for X-ray shielding have recently been relaxed considerably. This is not something for anyone to worry about. It’s not a matter of trusting the manufacturers to keep the X-ray emissions down. The old problem was from high voltage tube circuits which are now totally obsolete. The modern solid-state circuitry used in all of today’s television sets don’t act as X-ray sources to any meaningful extent. (Remember, your own body emits some X rays.) The old required shielding serves no particular purpose, because what it shielded against is no longer being generated in the first place.
A television set does emit some RF electromagnetic fields. These drop off quite quickly with distance. It probably wouldn’t hurt to avoid sitting too close to the television set, though it’s questionable as to just how harmful such energy is. It’s essentially the same as the broadcast signals that are always all around you whether you even own a television set or not. Proof that such emissions from the television receiver drop off quickly with distance are easy to come by. Place two television sets near each other, and tune them to different channels. They don’t interfere with each other, do they?
A lot has been written about computer monitors and radiation. Much of what has been said on this’ is pure nonsense. A computer monitor certainly is no more harmful than an ordinary television set, because electronically, they are virtually the same thing. The biggest difference is that a dedicated computer monitor doesn’t have any television tuner circuitry. Computer monitors are usually designed with a somewhat wider frequency response than ordinary television receivers, but this isn’t of any particular significance for the issue at hand.
The legitimate concern over computer monitors is that the user normally sits so much closer to the screen than someone watching television. Documented risks mostly concern eyestrain, back pains, and neck pains from holding an unnatural posture for extended times.
There might be some conceivable risk from the computer itself, as opposed to the monitor. The circuitry in a computer uses very high frequencies, and some high frequency electromagnetic fields are emitted. The power levels are usually quite low, however. There might be some risk, but it’s probably not severe.
To be on the safe side, it might be a good idea to alternate computer work with some other tasks away from its electromagnetic fields. The risk, if any, seems to be the result of prolonged rather than momentary exposure. Even the most rabid sensationalists seem to agree that exposure over time is the critical factor. Brief exposure to most electromagnetic fields is almost certainly of negligible importance.
-- Some tentative conclusions --
The author’s opinions on the subject follow so that you can compensate for any inadvertent bias in the discussion. There is little or no realistic risk from electromagnetic fields to the average citizen. There might be some subtle effects, but there are many far greater risks that you are constantly exposed to that this one seems rather negligible. Common household appliances are almost certainly not a significant threat. If you have any concern, the most reasonable response is to minimize usage and to keep a few feet away during normal use, if possible. Coming close to operate controls would not substantially increase any risk—it is prolonged exposure that counts, if anything.
The more or less constant electromagnetic fields from your ac electrical wiring in the walls will almost certainly swamp out the electromagnetic fields emitted by almost any home-size appliance unless you remain in abnormally close contact with it for extended periods. The electromagnetic fields generated by the house wiring are always there, whether you are using any appliances or not.
However, if you live directly under a power-line transfer point or work in a power plant or some other installation with a lot of heavy-duty electrical equipment, the electromagnetic field levels you are exposed to might be abnormally high. Greater research is needed to determine exactly what the true effects are, if any, and what can be down about the problem. What type of shielding would be effective? How much is too much?
If you are concerned about nearby power lines, most electrical companies will do a electromagnetic field reading for you at no cost, or for only a small fee. This could help set your mind at ease.
The most likely effects, if any, from prolonged exposure to electromagnetic fields seem to be in the form of increased stress stimulation. A great many factors can contribute to stress. Stress can cause many health problems, some even fatal, and its effects are often cumulative, so this is not an entirely trivial concern.
There have been experiments showing that sounds just outside the audible spectrum (either very low or very high) can cause stress effects. Perhaps the risk element is not really ELF fields at all, but an irritating sub-audible tone. This is just a casual top-of-the-head suggestion. It’s not intended as a serious scientific hypothesis, just a vague possibility. Perhaps you might want to try to devise some small experiments to test this idea.
At the very worst, the health risks from electromagnetic fields (if they exist at all) are subtle and indirect. The issue calls for greater examination and research, but it’s hardly grounds for panic, or even widespread concern among the general population. There are many far worse problems and risks facing us. The potential health risks of electromagnetic fields should not be ignored, but they shouldn’t be blown out of all realistic proportion either.
It’s not a major threat or critical health crisis. It’s been the author’s experience that the people who make the most noise about the alleged health risks of electro magnetic fields tend toward being a bit technophobic overall, mistrusting all technology in general. This does not prove that there is no risk at all, of course. But it does suggest that the potential risks are probably being exaggerated.
1. Which of the following cannot be used to make a magnet?
2. What are the ends of a magnet called?
E None of the above
3. What is another name for magnetic lines of force?
C Magnetic pole
E None of the above
4. If like poles of two magnets are brought near each other, what will happen?
A They will attract each other
B They will be damaged
C They will repel each other
D An electrical current will be generated
E None of the above
5. What is the magnetic equivalent to electrical voltage?
B Magnetomotive force
D Magnetic field
E None of the above
6. What is the magnetic equivalent of electrical current?
B Magnetomotive force
D Magnetic field
E None of the above
7. What is the magnetic equivalent to electrical resistance?
B Magnetomotive force
D Magnetic field
E None of the above
8. How can an electrical current be induced with a coil and a magnet?
A Placing the coil at right angles to the magnetic field
B Placing the coil parallel to the magnetic field
C Holding both the magnet and the coil perfectly stationary
D Moving either the magnet or the coil
E None of the above; it can’t be done
9. Rotating an armature in a magnetic field produces what type of electricity?
D Pulsating dc
E None of the above
10. What is the frequency range for an ELF field?
A 0-100 Hz
B 100-1000 Hz
C 500-1000 Hz
D 100-5000 Hz
E None of the above
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Updated: Thursday, 2016-12-22 9:57 PST