Reviewing a middle-school book in the Prentice Hall Science Series

This Book Is an Insult

Lawrence S. Lerner

The writers step off with a display of bad pedagogy that is antiscientific to boot. The spread that opens chapter 1 is evidently intended to reinforce the phony, scary impressions of "science" (including the fearsome image of the mad scientist) that young people acquire from movies and from television programs.

The left-hand page of the spread depicts Frankenstein's castle, and we see the obsessed doctor himself -- the Hollywood version, not the Mary Shelley version -- as he uses huge electrical sparks to further his nefarious schemes. The caption says, "Dr. Frankenstein at work in his laboratory."

The right-hand page has text that says:

Creepy characters . . . dark nights . . . thunder and lightning crashing in the background . . . castles with trap doors and secret laboratories. Do these descriptions sound familiar to you? Perhaps you have seen them in monster movies such as Frankenstein and The Bride of Frankenstein. These exciting movies often express people's hidden hopes and fears about a world in which scientific knowledge can be used for either good or evil. Usually, electricity is used at some point in the movie to mysteriously [sic] create life or destroy it.

Why would anyone, if he really were interested in inviting young people to learn science, begin by confusing and misleading them with recollections of horror movies? Prentice Hall's writers could have opened with a vignette about Benjamin Franklin, the versatile genius whose electrical experiments made him one of the most respected scientists of his day. Or they could have told of Michael Faraday, who not only conducted illustrious studies of electromagnetism but also gained fame as a masterful teacher, intent on bringing science to the public. Instead, the writers babble about Frankenstein! I infer that they know so little of science and history that they can't understand or admire the real people who have carried science forward. For these writers, science is an image of an evil monster.

Maybe you are hoping that they have introduced Hollywood-style "science" as a straw man, and that they soon will demolish it. Not so. Look at what they say next: "For hundreds of years, many people were frightened by electricity and believed it to have mysterious powers. Today a great deal is known about electricity. And although it is not mysterious, electricity plays a powerful role in your world." The writers thus imply that most things which play powerful roles in our world are mysterious, that electricity is an exception, and that we should find it remarkable that something can have great practical importance without being inscrutable. Eventually, though, the writers let us know that electricity is just as mysterious as anything else, and that the best we can do is to "believe" things about it. Hence they employ trite phrases (such as "Many scientists believe . . .") that demonstrate gross ignorance of the ways in which scientists reach conclusions and consensus. On page 50, to cite one example: "Scientists believe that the atom itself has magnetic properties." Wrong. This is not a matter of idle belief. Atoms have magnetic moments. The direct measurement of such moments is routine work in physics and chemistry, and it has life-saving applications in medicine.

The most egregious errors in this book are those that deal with fundamental concepts. Such errors bar students from learning subsidiary ideas or applications, and they testify to the Prentice Hall writers' profound ignorance of the subject matter.

On page 14 we read, "An electric field is an area over which an electric charge exerts a force." No. A cornfield may be an area, but an electric field is not. In fact, the concept of a field is rather subtle, and it needn't have been introduced so early in the book.

Page 24 introduces some protracted confusion concerning basic terms: potential, potential difference and the loosely synonymous voltage. After an incomprehensible "explanation" of an electrochemical cell, the writers say: "The difference in charge [between the terminals of an electrochemical cell] is called a potential difference." If you don't like that misdefinition, there is a different one on page 27, where a potential difference is equated with an electric current. There is still another on page 30 of the teacher's edition, where a note tells the teacher that "Voltage is the energy available to move electrons." (Now I'll tell the right answer: Potential difference is a measure of potential energy per unit charge.)

The writers' confusion about potential and voltage yields more nonsense. On page 27, "an electric ray . . . can discharge about 200 volts of electricity." (What is a volt of electricity? And how does a ray, or a scientist, "discharge" one?) On page 38, the student reads a warning: "Never come close to wires on power poles or to wires that have fallen from power poles or buildings. Such wires often carry very high currents." But it's the voltage, not the current, that makes wires dangerous, and we now are aware of a key point: The writers don't grasp the difference between voltage and current.

The writers' attempt to describe the unit of current is on page 25: "The ampere, or amp for short, is the amount of current that flows past a point per second." If that were true, then every current would be a current of 1 ampere, and the term ampere would have no quantitative meaning! Here is the correct definition: One ampere is the amount of current that flows when one coulomb of charge passes a given point every second. Prentice Hall's ignoramuses have missed the target by a country mile. (The coulomb doesn't appear in the student's text, but the teacher finds it in a "Background Information" note on page 24. The writers try to quantify it, but they are wrong by a factor of 10 billion!)

Now, on to Ohm's law! On page 28 a note tells the teacher that Ohm "was the first to define the relationships among voltage, current, resistance, and power." (No, that was done by Kirchhoff and by Joule.) Then the note says, "Many people believe that Ohm's law is the most important single electric formula a student will ever learn." Why? And who are those "people"? My guess is that Prentice Hall's writers want to endow Ohm's law with monumental significance because it is one of the few electrical relationships that they know how to write.

The fact that these writers can recite Ohm's law doesn't mean they understand it, and they soon show that they don't understand it. They have heard that resistance is measured in ohms, but their definition of the ohm (involving a column of mercury of known mass and length) is obsolete and wrong. Today, the ohm is defined as one volt per ampere. In other words, the ohm is no longer a base unit. It is a derived unit.

The mistakes pile up, showing that the writers are just guessing their way through material that is far beyond their comprehension. On page 28, a caption says that a light-bulb filament "offers enough resistance to the electric current flowing through it so that heat and light are given off." On the same page, a note tells the teacher to afflict students with this question and answer: "If a different filament with more resistance is used, what should happen to the light bulb? (It should be brighter.)" No -- given the same source of power, the bulb will be dimmer.

Now the writers maul Joule's law. In the text on page 36, the law is stated correctly: Power = Voltage x Current. But in a teacher's note, "Voltage" is replaced by "Force." This is not an isolated mistake, for the writers soon show that they don't really know what power is. A table gives power ratings for various electrical appliances, and the caption asks, "Which appliance would use the greatest number of watts if operated for one hour?" The correct answer is: Time has nothing to do with this, and the writers are confusing power with energy. (The writers' "answer" is that the greatest number of watts would be consumed by a 2,600-watt "range/oven," even though the appliances also include a 4,000-watt clothes-dryer!)

Next, magnetism. Throughout the section about magnetism, the writers evidently cannot decide whether magnets attract all metals or only ferromagnetic metals. The properties of superconductors are stated incorrectly, and the writers imagine that all superconductors are metals. Wrong.

When they get to electromagnetism, the writers don't even try to state Ampère's law or Faraday's law. (A note to the teacher, on page 80, wrongly gives the name "Faraday's law" to a rather unimportant equation that relates a transformer's voltage ratio to its turns ratio.) When they try to tell what Faraday did, they cook up the notion that "the one common element" in all his experiments was a changing magnetic field. That's exactly what Faraday's experiments showed was not the case.

The subject matter of chapter 4, "Electronics and Computers," is more concrete than that of the first three chapters, but the writers' work does not improve.

The chapter starts out with a totally botched discussion of vacuum tubes. The cathode and the plate of a vacuum diode are called the "emitter" and the "collector" -- names that apply to parts of a transistor but are never used in describing vacuum tubes. On page 89, a tube's filament heats both electrodes. (If this were true, the tube would conduct current in both directions and would not function as a rectifier, much less as an amplifier. On page 90, the description of a triode is nonsensical.

Next, semiconductor physics. On page 92 the student reads this:

If a semiconductor is doped with a material whose atoms have three outermost electrons . . . there will be empty holes in the semiconductor's crystal structure. These holes can also be used to form a current.

The writers do not know what hole means, and their guess is wrong. What they call a "hole" -- an empty site in a crystal -- is what scientists call a vacancy. Vacancies don't have anything to do with electron deficiencies, don't "form a current," and don't explain the behavior of semiconductors. The rest of the discussion of semiconductors is useless, and a pedagogic note invites the teacher to play the fool: "Emphasize how the transistor is a miniature triode vacuum tube." A transistor is no such thing, though transistors and triodes sometimes carry out analogous functions.

The description of integrated circuits is pure moonshine. Integrated circuits do not consist solely of diodes and transistors, and their internal connections are not made by "painting" or "scratching."

That jockey comes to mind as I survey the pedagogic notes in which Prentice Hall's writers evidently try to impress the teacher with gee-whiz stuff. They succeed only in betraying their ignorance and confusion, as in these examples:

• On page 18, in an "Integration: Mathematics" note: "The magnitude of the force in an electric field is proportional to the product of the charges of the two objects, divided by the square of the distance between them." But the book has not given and never will give a method of quantifying electric charge.

• Page 30: The student reads questions that he cannot answer correctly, given the misinformation in the text. The answers furnished to the teacher are wrong, incomprehensible or unresponsive.

• Page 57: "Suggest that students research to find out what light pollution is and how it might be controlled so that people can enjoy such phenomena as the aurora." Now, just how would students "research" such things? In any case, most of the United States lies at such low magnetic latitudes that the aurora is rarely, if ever, visible -- light pollution or no.

• Page 59: The student's text tells about sea-floor spreading, mentions magnetic stripes, and says that "the pattern of magnetic stripes on one side of [a mid-ocean] ridge matches the pattern on the other side." A pedagogic note says that the teacher can model this by "drawing horizontal lines on a sheet of paper and then tearing the paper vertically." But magnetic stripes lie parallel to a mid-ocean ridge, not perpendicular to it, so the model is nonsense.

• Page 70 has another "Integration: Mathematics" note. After giving a formula for finding an electromagnet's "magnetomotive force," the writers say: "The strength of any electromagnet depends on the amount of current and the number of amperes. . . . Have interested students use the formula to determine the strength of the electromagnets used in this chapter." First, "the amount of current" is "the number of amperes" -- the writers are wrong in guessing that these are different things. Second, the term magnetomotive force is not defined. And third, the students can't do the suggested task because they don't have data for the magnets "used in this chapter."

• On page 85 an "Issues in Science" note tells the teacher about nuclear power plants: "After the steam is used [to drive a turbine] it is released into the atmosphere, and the warm water is piped to cooling ponds for reuse after it is cooled." Doubly wrong. First, in any thermal generating plant (nuclear or otherwise) the spent steam is condensed, and the condensate is returned to the boiler. Venting the steam to the atmosphere would waste water and energy, and the plant's thermodynamic efficiency would be unacceptably low. Second, if the steam were vented to the atmosphere, no "warm water" would be recovered, and none could be "piped to cooling ponds."

Read page 63 of the teacher's edition, where a note offers two "issues" for use in discussions or in written work. The first involves a notion that "harmful charged particles" and "harmful rays" pose a serious danger to astronauts. The writers evidently don't know that scientists and engineers have given thought to this matter, and that satisfactory solutions are in hand. It would make sense to ask students to learn about the R&D work that led to these solutions, but it makes no sense to ask the students to take positions based on ignorance.

Now, here is the second "issue":

Research in nuclear fusion is costly and time consuming. Should the research continue because alternative fuel sources are needed, or should the research be discontinued and the money and time allocated to address other needs, such as cures for fatal diseases?

That is utterly irresponsible! Competent teachers never mislead students and promote sloppy thinking by setting up false dichotomies! One might as well force a choice between bread and oranges: Should we abolish wheat-farming and turn all the wheat farms into orange groves? -- or should we destroy all our orange groves and convert the land to wheatfields? That "problem" makes just as much sense as Prentice Hall's false choice between fusion research and medical research.

• On page 41 an "Enrichment" note for the teacher says that a little electric cell, built by students, "should produce a current of about 0.5 volts." The writers are still confusing current with voltage.

• Page 70: "Sewing machines, refrigerators, vacuum cleaners, power saws . . . are a few of the many devices that would be practically impossible without electric motors." More wrong guesses. Treadle-driven sewing machines were common, both in homes and in factories, for the better part of a century. Refrigerators powered by gas or by kerosene were common in the United States until 1940 or so, and they're still used in some other parts of the world. Gasoline-powered chain-saws are so common, here and now, that I have to wonder how the Prentice Hall writers have remained unaware of them.

• Page 71: After giving a wrong explanation of the moving-core solenoid, the writers say that this device is used in automobile starters. They then confuse a starter relay with a Bendix gear -- a linkage between the starter-motor shaft and the engine.

• Pages 70 and 71: The three illustrations on these pages include six errors. For example, the electric motor in figure 3-6 will not turn, and (for three different reasons) the "doorbell" shown in figure 3-8 won't function.

Electricity and Magnetism fits right in with the other Prentice Hall Science books that I have reviewed. It is a travesty -- an insult to teacher and student alike.

Lawrence S. Lerner is a professor in the Department of Physics and Astronomy at California State University, Long Beach. His specialties are condensed-matter physics, the history of science, and science education.

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