This apparatus demonstrates how an iron core with two poles wrapped in wire becomes a magnet when connected to electricity, and how it can cause another wire-wrapped iron core (i.e. another electromagnet) to rotate as a simple motor. In this device, the revolving electromagnet spins between the poles of the fixed electromagnet as the current is fed to the latter by a “pole changer,” or commutator.
Max Kohl Aktiengesellschaft (A.G.) was a German manufacturer of apparatus and equipment for science, technology and industry, based in Chemnitz. The founder, Max Kohl (1853-1908), was a major entrepreneur in the field of electrical engineering, optics and precession mechanics. He studied at Royal Höhere Gewerbeschule in Chemnitz, but left without a degree. After an apprenticeship with a mechanic, in 1876 he founded his own precession mechanics workshop. He soon expanded into electrical engineering. Eventually Max Kohl A.G. supplied measuring instruments to the textile industry; laboratory furniture; and electrical equipment for lighting, electrical, telephone, signal and clock systems. In all, the product range encompassed around 4,000 devices. The firm sold to laboratories and educational institutions all over the world and published catalogs in English as well as German. Over time chemical apparatus and X-ray equipment were added to the product line. After Kohl died in 1908, the firm became a public limited company.
Max Kohl A.G. Physical Apparatus in Stock. Chemnitz, Germany. pp. 61-62. http://www.sil.si.edu/DigitalCollections/trade-literature/scientific-instruments/CF/SIsingle-record.cfm (14 September 2018).
Mohammad, Jasmin. “Kohl, Max Hans Robert” in
Saxon Biography, ed. from the Institute for Saxon History and Folklore, Martina Schattkowsky, ed. 3 December 2012. Online at: http://saebi.isgv.de/biografie/Max_Kohl_(1853-1908) (14 September 2018).