Leo Graetz (26 September 1856 – 12 November 1941) was a German

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

. He was born in Breslau, Germany, and was the son of historian

Heinrich Graetz Heinrich Graetz (; 31 October 1817 – 7 September 1891) was amongst the first historians to write a comprehensive history of the Jewish people from a Jewish perspective. Born Tzvi Hirsch Graetz to a butcher family in Xions (now Książ Wielko ...

. Graetz was one of the first to investigate the propagation of

electromagnetic energy In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions o ...

. The

Graetz number In fluid dynamics, the Graetz number (Gz) is a dimensionless number that characterizes laminar flow in a conduit. The number is defined as: :\mathrm = \mathrm\, \mathrm where : ''DH'' is the diameter in round tubes or hydraulic diameter in a ...

(''Gz''), a

dimensionless number A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1) ...

describing

heat flow Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

, is named after him. Also sometimes known by his name is the

diode bridge A diode bridge is a bridge rectifier circuit of four diodes that is used in the process of converting alternating current (AC) from the input terminals to direct current (DC, i.e. fixed polarity) on the output terminals. Its function is to con ...

rectifier circuit that was invented by Polish electrotechnician Karol Pollak in 1896 and that was independently invented and published by Leo Graetz in 1897. In 1880 he confirmed the

Stefan–Boltzmann law The Stefan–Boltzmann law describes the power radiated from a black body in terms of its temperature. Specifically, the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths ...

. Graetz died in

Munich Munich ( ; german: München ; bar, Minga ) is the capital and most populous city of the German state of Bavaria. With a population of 1,558,395 inhabitants as of 31 July 2020, it is the third-largest city in Germany, after Berlin and Ha ...

at age 85.

Publications

* ''Die Elektrizität und ihre Anwendungen'' (''Electricity and Its Applications''), Stuttgart 190
Digital 17th edition from 1914
by the University and State Library Düsseldorf * ''Handbuch der Elektrizität und des Magnetismus'' (''Handbook of Electricity and Magnetism'') - 5 volumes, 1918, 1921, 1923, 1920, 1928 * ''Recent developments in atomic theory'', 1922

References

1856 births 1941 deaths 19th-century German physicists People from the Province of Silesia Scientists from Wrocław Fluid dynamicists 20th-century German physicists {{Germany-physicist-stub