= Wander Johannes de Haas
{c}
{tag=Physicist}
{title2=1878–1960}
{wiki}
= Wander de Haas
{c}
{synonym}
= W. J. de Haas
{c}
{synonym}
<Wander Johannes de Haas> and <Albert Einstein> investigated mechanical motion produced by changing the <magnetization> of a suspended body. Magnetic reversal changes microscopic <angular momentum>; a compensating rotation of the body tests angular-momentum conservation. Their experiment connected an apparently internal magnetic property with a visible mechanical response. Interpreting a gyromagnetic measurement requires the relation between <magnetic moment> and <angular momentum>, rather than treating <magnetization> as a force acting independently of its microscopic carriers.<Experimental proof of the existence of Ampère's molecular currents by Albert Einstein and Wander Johannes de Haas>[1915 report, magnetic reversal and mechanical rotation experiment]{ref}
A <physicist> who researched <magnetism> and became a professor at Leiden in 1924.<Wander Johannes de Haas, 1878–1960 by H. B. G. Casimir>[Career paragraphs: PTR research staff 1913–1915; Delft, Groningen and Leiden professorships]{ref}
\Image[https://commons.wikimedia.org/wiki/Special:Redirect/file/Heike_Kamerlingh_Onnes_-_53_-_Wander_Johannes_de_Haas_(1878_-_1960),_in_1924_together_with_Willem_Keesom_(1876_-_1956).png?width=260]
{title=Portrait of <Wander Johannes de Haas>}
{description=Unknown photographer; Huygens Laboratorium, Universiteit Leiden; reproduced in Dirk van Delft, Heike Kamerlingh Onnes: Een biografie (2005), p. 529. Public domain (author life plus 70 years; published before 1931). https://creativecommons.org/publicdomain/mark/1.0/[Source usage terms], via Wikimedia Commons.}
{source=https://commons.wikimedia.org/wiki/File:Heike_Kamerlingh_Onnes_-_53_-_Wander_Johannes_de_Haas_(1878_-_1960),_in_1924_together_with_Willem_Keesom_(1876_-_1956).png}
{width=260}
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