Bibliography

E. Grimsehl. A Course of Physics for Students, Teachers, and Self-Study, vol. II, issue 1, Electromagnetic Field, translated under the editorship of Prof. A. I. Bachinsky, 644 pp., ONTI, Main Editorial Office of Technical-Theoretical Literature, Moscow–Leningrad, 1938, price bound 17 rubles 15 kopecks.

E. Grimsehl’s course of physics is well known to the Soviet reader and needs no recommendation. The volume under review, covering the foundations of the theory of electromagnetic phenomena, contains material set forth in the fourth volume of the Russian edition of 1930, as well as several additional chapters (electromagnetic oscillations and waves). The new edition, however, has been so thoroughly revised that in essence it represents a new book.

Whereas in the old edition the main attention was devoted to the experimental side of the subject, and theoretical questions were to some extent relegated to the background, in the present edition an attempt has been made at a systematic exposition of electromagnetic phenomena from the standpoint of Faraday–Maxwell field theory, with each theoretical proposition illustrated by a whole series of well-chosen experimental facts. This gives the exposition considerable coherence and is a positive feature.

It is also highly valuable that the author has succeeded in presenting the theory of magnetic phenomena without resorting to the idea of magnetic mass, but operating only with the concepts of field strength and magnetic moment, introduced by analogy with the corresponding concepts from electrostatics.

Further, throughout the book only one system of units is used systematically—the practical one. It is, of course, possible to argue about which system of units should be used in physics (see, for example, the considerations expressed on this subject by Becker in the book Abraham Becker: Theory of Electricity, pp. 5–6, Moscow–Leningrad, 1936); but one can hardly doubt that encumbering a course with various systems of units is unnecessary. True, for the majority of physicists brought up on older textbooks, the practical system of units is not very customary; when using it some familiar formulas take on an unusual appearance. Yet it seems to us that the reader beginning the study of physics should first of all become acquainted with the units most suitable for practical needs. As for theoretical physics, where the Gaussian system is more “justified” on fundamental grounds, it should be borne in mind that hardly the majority of readers of E. Grimsehl’s course will work in the field of theoretical physics. Therefore, from the standpoint of the interests of the majority, the choice of the practical system of units should be welcomed.

The least successful chapter is “Oscillations and Waves.” Thus, on pp. 562–563 the description of the oscillatory discharge is made in the following manner, which requires no comment: “The electrical energy of the capacitor thus flows through the spark into the coil of the oscillatory circuit and is accumulated there in the form of magnetic energy. The current disappears and the spark goes out; the magnetic field disappearing as a result of this induces a voltage which again charges the capacitor,” etc. “In this way the energy of the magnetic field disappears after the current has ceased.”

On p. 589 it is stated that moving the slider in Lecher’s system changes the inductance of the latter, but not a word is said about the simultaneous change in capacitance, i.e. the principal point is overlooked—the distributed constants of the system.

On pp. 591 and 592 it is reported that, in a system with distributed constants, the current in some of its sections is “delayed” (!).

In comparing mechanical and electrical oscillations and mentioning the analogy between kinetic energy and the energy of the magnetic field (p. 551 ff.), the author does not deem it necessary to compare potential energy with the energy of the electric field of the capacitor, as a result of which his analogy loses clarity. A formal comparison of capacitance and elastic constant does, to be sure, exist, but it is set in small type and may go unnoticed.

On p. 572 it is reported that a magnetic blowout contributes to cooling the arc, although its role is primarily reduced to deionization. Ion and electron lamps are interpreted rather vaguely. On p. 574 we learn that with an increase in anode voltage the density of the space charge increases. On p. 580 it is said that the magnitude of the resistance of the anode circuit (in an amplifier) is chosen equal to the internal resistance of the tube. This is true only for power amplifiers, whereas the text is speaking of voltage amplifiers.

On Fig. 752 a capacitor is connected in the anode circuit of a tube (in series with the anode battery and the tube), the role of which remains mysterious.

On p. 596, where the mechanism of propagation of an electromagnetic wave in a Lecher system is explained, it is said that the electric and magnetic fields push each other with the speed of light (?!). On p. 602 the energy in a closed oscillatory circuit is called stored (!), while in a standing wave there occurs “reversible transfer of oscillations.”

On p. 607 we learn that the energy radiated by a vibrator is proportional to the frequency of oscillations.

In Fig. 792 a circuit of a radio station powered by a six-phase rectifier is shown. However, the feeding of the rectifier itself is depicted in such a way that even a qualified reader will not at once understand what the matter is, since the book says not a word about six-phase currents; the figure needs explanation.

It is to be regretted that, in translating the last chapter, use was not made of the brilliant exposition of electromagnetic oscillations available in the well-known book by Tamm.

The remaining chapters are set forth incomparably better. Among the individual shortcomings, the following deserve mention:

1) the absence of a description of thermoelectric devices,
2) the absence of any mention of the possibility of obtaining an emf of induction by means of a permanent magnet, which from the pedagogical standpoint is far from superfluous,
3) the absence of a description of high-voltage installations, in particular the Van de Graaff generator,
4) in the discussion of electrical resonance (p. 479) no sufficiently clear formulation is given of the distinction between resonance of currents and resonance of voltages,
5) the treatment of the star and delta circuits (p. 497) ends with absolutely unintelligible phrases such as: “Therefore in one case for the voltage, and in the other for the current, smaller dimensions of the individual wires may be taken,”
6) the distinction between magnetic-field strength and induction is not always drawn clearly enough, as a result of which on p. 402 we learn that a current flowing through a toroid creates in it a field of different strength (depending on the substance filling the toroid). This may create irremediable confusion for a poorly prepared reader,
7) on p. 430 the process of establishing a steady current in a circuit with inductance proves to be a function of voltage, for which even a special explanation is given (of course, incorrect).

“Unconditional,” as the editor writes, “following of the views”

Faraday–Maxwell sometimes leads to rather unfortunate formulations; thus, on p. 116 we read: “The obtaining of electricity by friction is nothing other than the stretching of molecular force lines” (italics in the book), and on p. 66 “force lines flow down from the conductor,” for which, however, it is not so much Grimsehl as the translator who is to blame.

As for the translation, in some places it has been done rather unsatisfactorily. Thus, on p. 76 Gauss’s theorem is formulated “for the surface enclosing all the charges,” which gives the impression that it is a question of the possibility of constructing a Gaussian surface lying inside the charges, and introduces an element of ambiguity.

On p. 144 it is stated that, in the process of charging a capacitor, the charges rapidly move toward one another.

The translator attributes the photographs of electron tracks in Wilson’s chamber (Figs. 414 and 415) to Meitner, evidently unaware that the well-known investigator of the atom, L. Meitner, is a woman.

On p. 414, during the remagnetization of a ferromagnetic material, “the energy disappears, i.e. is transformed into heat.”

On p. 392 the general formulation of the law of induction begins with the following words, printed in bold type: “An alternating magnetic current ...,” although in the original, of course, it is a magnetic flux.

In Fig. 119 the translator did not understand the inscription; the word “Piezorichtung,” i.e. the direction in which the crystal is piezoelectric, he translated as “direction of pressure”; since, moreover, in reproducing the drawing an arrow indicating this direction was lost, the figure has become completely unintelligible.

The most serious error made in the translation is the distortion of the entire doctrine of alternating currents.

Three times (pp. 459, 463, 466) the translator says that in a circuit “there arises a current ..., an electromotive force which is opposed to the action of the external electromotive force has a retardation (or advance) in phase,” after which follows the usual equation for the angle of phase shift between the current and the external electromotive force.

In the original this important proposition is formulated correctly: it speaks of a phase shift between the current and the acting (external) electromotive force.

The formulation given in the translation, being repeated three times and emphasized in italics, introduces irreparable confusion that completely distorts the whole chapter on alternating currents and will probably cause no little trouble for readers of the book—students and their teachers.

In a number of cases the translator permits very careless formulations. Among these are “an obicirny field” (p. 551), “wattless current” (p. 576), although on p. 473 it was indicated that the term “wattless” is replaced by the term “reactive.” On p. 200 mention is made of the “laws of electromagnetics.” On p. 623 we read: “a light ray ... is an electric vector.”

On p. 138 the characteristics of the earth’s magnetic field are given for Germany, and on p. 296 the output of American industry is valued in marks (!). These passages should have been altered for the Russian translation.

On p. 413 the initial magnetization curve is called “virginal”—a literal translation of the German “jungfräuliche Kurve,” not accepted in Russian literature.

Finally, on p. 291 the word “we use” (!) occurs. The exposition of the theory of ferromagnetism should have been supplemented with information on the work of Prof. Akulov.

The book contains a number of unnoticed but substantial misprints. On p. 48 the word “often” has lost its “part,” thereby completely distorting the meaning; in the table on p. 92 the dielectric constant of acetone is \(\varepsilon = 1.85\), instead of the correct \(\varepsilon = 21.5\); Fig. 547 duplicates Fig. 553, although this should not be so; in the formula on p. 479 there is an error in the sign; on p. 573

100 volts (anode voltage) have turned into 10 V; on p. 625 “macroscopic” have turned into “microscopic.” Fig. 806 is rotated by 90° in comparison with the illustration described in the text, so that the reader has to guess that “left” means “below,” and so on.

Finally, the repeated references to the third issue of this volume are perplexing, whereas the editors, judging by their statement (p. 3), do not intend to publish it.

The book is printed, on the whole, satisfactorily, but some figures have come out indistinct (Figs. 224, 251, 286, 697), and the scale of the figures is generally somewhat too small.

The price of the book—17 rubles 15 kopecks—is disproportionately high, especially if one considers that the book will probably go through more than one edition and that the main body of purchasers is students. It is time, at last, to put before publishing houses the question of the need to make mass textbooks cheaper.

Despite the shortcomings indicated, which can easily be corrected in subsequent editions, one must warmly welcome the appearance of this book and wish for the speedy publication of the remaining volumes of Grimsehl’s course.

N. Malov, Moscow