Eichenwald, Aleksandr Aleksandrovich

(b. St. Petersburg, Russia, 4 January 1864; d. Milan[?], Italy, 1944)

physics, engineering.

Eichenwald’s father was a photographer and artis; his mother, a professor of harp at the St. Petersburg Conservatory and, later, a soloist of the Bolshoi Theater orchestra in Moscow. His sisters and brother were also professional musicians, and he himself was a pianist and a connoisseur of music, which stimulated his interest in acoustics.

While in high school, from which he graduated in 1883, he formed his friendship with the future physicist P. N. Lebedev. After completing two years of study at the Faculty of Physics and Mathematics of Moscow University, Eichenwald entered the St. Petersburg Railway Institute, from which he graduated in 1888. After working for seven years as an engineer, he went to Strasbourg to continue his education and devoted himself to physics. K. F. Braun was his instructor in experimental physics, and Emil Cohn in theoretical physics. His Ph.D. dissertation was entitled “Absorption elektrischer Welled bei Elektrolyten” (1897).

From 1897 to 1921 Eichenwald worked at the Moscow Engineering College (now the Moscow Institute of Railway Engineers). In the excellent scientific laboratory that he organized there, he carried out the fundamental experiments described in his dissertation for a Russian doctorate, O magnitnom deystvii tel, dvizhushchikhsya v elektrostaticheskom pole (“On the Magnetic Action of Bodies Moving in an Electrostatic Field”, 1904), and undertook investigations of the propagation of electromagnetic and sound waves. In 1905–1908 Eichenwald was director of the Institute of Railway Engineers and from 1901 was also an instructor at the Higher Women’s Courses and, in 1906–1911, at Moscow University. After Lebedev’s death he headed the Moscow Physics Society, which Lebedev had founded. In 1917–1920 he participated in the reorganization of higher education. After two operations in Moscow and Berlin for cancer, Eichenwald moved to Milan, where he wrote textbooks that were published in the Soviet Union. His textbook on electricity saw eight editions from 1911 to 1933. In 1926–1932 the first three and the sixth volumes of Theoretical Physics were published.

Eichenwald was simultaneously a keen experimenter, a serious theoretician, a brilliant lecturer and methodologist, and an inventor of demonstration apparatus. He won world fame by his unquestionable proof that the motion of an electrically charged body produces an electric field, by his exact proof of the equivalence of convection and conduction currents, and by the first proof, based on direct measurements, of the existence of a magnetic field when the polarization of a dielectric changes, i.e., a magnetic field of a displacement current (1901–1904).

By his direct and accurate experiments on the detection and measurement of the magnetic field of convection currents, Eichenwald completed the final step in a series of experiments with contradictory results that had been started by H. A. Rowland (1876) and continued by V. Grémieu, Ernst Lecher, and Harold Pender (1902).

Besides the magnetic field created by the motion of charged conductors, Eichenwald measured the currents produced by the motion of a dielectric in a nonuniform electric field (they had been discovered by Roentgen in 1888) and organized a new type of experiment (the Eichenwald experiment), by means of which the existence of the magnetic field of the displacement current in dielectrics was established and its magnitude was measured for the first time.

Half of a disk made from a dielectric and rotating about its axis passed constantly between the plates of one capacitor, and the other half between those of another capacitor. The electric fields in the capacitors were oppositely directed. When each element of the dielectric passed from the zone of one capacitor to that of the other, the polarization of this element became the opposite of what it had been. Eichenwald discovered the magnetic field of the displacement current appearing in the dielectric by observing the change in the oscillations of a small magnetic needle when the disk was stationary and in motion. The needle was arranged so as not to react to convection currents. The experiment was organized in connection with the question of the conduction of ether by moving bodies. The result conformed with the theories of H. A. Lorentz and E. Cohn, in which motionless ether was assumed, but after the appearance of the theory of relativity Eichenwald proved that his experiment could be interpreted in accordance with the new concept.

In “O dvizhenii energii pri polnom vnutrennem otrazhenii sveta” (“On the Motion of Energy With Complete Internal Reflection of Light,” 1908), Eichenwald completely explained this phenomenon from the standpoint of J. C. Maxwell’s electromagnetic theory of light, indicating the reason for Drude’s error. (According to Drude’s theory of the motion of light energy along a reflecting surface, the direction of the vector of the electric field coincides with the direction of this motion, instead of being perpendicular to it.)

The equations deduced in this work, reflecting the curvilinear nature of the propagation of light in a reflecting medium, were also applicable in other cases and were published in a generalized form in “Das Feld der Lichtwellen bei Reflexion und Brechung” (1912).

In the investigation “Akusticheskie volny bolshoy amplitudy” (“Sound Waves of Large Amplitude”), a different, simpler, and physically more illustrative method of calculation than that of Riemann was proposed for strong sounds, when the approximate equations of wave propagation cannot be used.

BIBLIOGRAPHY

I. Original Works. Some of Eichenwald’s works ware collected as Izbrannye trudi (“Selected Works”), A. B. Mlodzeevsky, ed. (Moscow, 1956), with remarks and a biographical essay. Among his writings are “Absorption elektrischer Wellen bei Elektrolyten,” in Annalen der Physik und Chemie, 62 (1897), 571–587; “Über die magnetischen Wirkungen elektrischer Konvektion,” in Jahrbuch der Radioaktivität und Elektronik, 5 , no. l (1908), 82–98—see also L. Graetz, Handbuch der Elektrizität und des Magnetismus, II (Leipzig, 1914), 337–365; “O dvizhenii energii pri polnom vnutrennem otrazhenii sveta” (“On the Motion of Energy With Complete Internal Reflection of Light”), in Izvestiya Moskovskago inzhenernogo uchilishcha (Apr. 1908), 15–14—see also Annalen der Phsik, 35 (1911), 1037–1040; “Das Feld der Lichtwellen bei Reflexion und Brechung,” in Festschrift Heinrich Weber (Leipzig, 1912), 37–56; and “Akusticheskie volny bolshoy amplitudy” (“Sound Waves of Large Amplitude”), in Uspekhi fizicheskikh nauk, 14 , no. 5 (1934), 552–585—see also Rendiconti del Seminario matematico e fisico di Milano, 6 , no. 10 (1932), 1–28.

II. Secondary Literature. On Eichenwald and his work, see N. A. Kaptsov, “Aleksandr Aleksandrovich Eichenwald,” in Uchenye zapiski Moskouskogo gosudarstvennogo universiteta, Jubilee ser., no. 52 (1940), 166–171; G. Mie, Elektrodynamik (Leipzig, 1952), pp. 51–54, 60–62; and A. B. Mlodzeevsky, “A. A. Eichenwald,” in Ocherki poistorii fiziki v Rossii (“Essays on the History of Physics in Russia,” Moscow, 1949).

O. Lezhneva