German physicist; son of Heinrich Graetz; born at Breslau Sept. 26, 1856. Graduating from the Elizabeth gymnasium at Breslau in 1875, he studied physics and mathematics at Breslau, Berlin, and Strasburg, taking his degree (Ph. D.) at the first-named university in 1879. In 1882 he became privat-docent in physics at the University of Munich; in 1893 he was appointed professor. His scientific papers, published chiefly in the "Annalen der Physik und Chemie," include treatises on the conduction and radiation of heat, on mechanics and hydrodynamics, but principally on electricity. He originated a method, now much used, for converting alternate into continuous currents, and was the first to experiment on the dispersion of electric waves. He contributed a number of articles to A. Winkelmann's "Handbuch der Physik," especially to the part dealing with heat and electricity.
Among his larger works are: "Die Elektricität und Ihre Anwendung" (Stuttgart, 1st ed. 1883, 10th ed. 1903), the most popular work on electricity in Germany; "Kurzer Abriss der Elektricität" (ib. 3d ed. 1903); "Compendium der Physik" (Leipsic and Vienna, 3d ed. 1902); "Das Licht und die Farben" (Leipsic, 1900).
- J. C. Poggendorff, Biographisch-Literarisches Handwörterbuch, iii. (to 1884), iv. (1884-1902);
- Eckstein, Das Geistige Deutschland, Berlin.