{"product_id":"dehaasa-einstein-de-haas","title":"Dehaasa – The Einstein–de Haas Effect \/ L = 2mμ\/(ge) Physics Sticker","description":"\u003cp\u003eDehaasa, a stern bald magister, holds a glowing golden coil wrapped round a hanging iron rod.\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eMagnetise an iron rod and it starts to turn. In 1915 Albert Einstein and Wander de Haas hung an iron cylinder on a fine fibre inside a coil (Verh. Dtsch. Phys. Ges. 17, 152). Reversing the magnetisation flips the tiny magnets inside the iron, and their angular momentum flips with them. Angular momentum is conserved, so the whole rod twists the other way. The ratio of magnetic moment to angular momentum sets the g-factor.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eL = 2mμ\/(ge)\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eL: angular momentum of the carriers (J·s)\u003c\/li\u003e\n\u003cli\u003eμ: magnetic moment (A·m²)\u003c\/li\u003e\n\u003cli\u003em: electron mass (kg)\u003c\/li\u003e\n\u003cli\u003ee: elementary charge (C)\u003c\/li\u003e\n\u003cli\u003eg: gyromagnetic g-factor\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eEinstein and de Haas reported g ≈ 1, as expected for orbiting electrons. That was wrong: careful later measurements gave g′ ≈ 2, the mark of electron spin, which was not yet known.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e In iron the measured g′ is about 1.9 because a little orbital moment remains; the effect is tiny and easily swamped by stray fields, which is how the 1915 result went astray.\u003c\/p\u003e\u003ch3\u003eOn the sticker\u003c\/h3\u003e\u003cp\u003eDehaasa holds a glowing golden coil with a thin rod running through it. Printed text: \u003cstrong\u003eDEHAASA\u003c\/strong\u003e with the line \u003cstrong\u003eL = 2mμ\/(ge)\u003c\/strong\u003e. Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.\u003c\/p\u003e","brand":"Printify","offers":[{"title":"2\" × 2\" \/ White","offer_id":50964112539751,"sku":"41635314557405560410","price":4.99,"currency_code":"USD","in_stock":true},{"title":"3\" × 3\" \/ White","offer_id":50964112572519,"sku":"74754989620692022769","price":6.99,"currency_code":"USD","in_stock":true},{"title":"4\" × 4\" \/ White","offer_id":50964112605287,"sku":"26263681671784982417","price":8.99,"currency_code":"USD","in_stock":true},{"title":"6\" × 6\" \/ White","offer_id":50964112638055,"sku":"21557631913348440895","price":11.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/4457171932301302905_1200.jpg?v=1793659919","url":"https:\/\/pixelatedphysics.com\/products\/dehaasa-einstein-de-haas","provider":"Pixelated Physics","version":"1.0","type":"link"}