{"product_id":"barnetta-barnett-effect","title":"Barnetta – The Barnett Effect \/ M ∝ Ω Physics Sticker","description":"\u003cp\u003eBarnetta, a hooded spinner, whirls a glowing iron rod upright in his hands.\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eSpin an unmagnetised iron rod and it becomes magnetised. Samuel Barnett showed this in 1915 (Phys. Rev. 6, 239): rotation acts on the electrons' angular momentum like a magnetic field, so their spins tend to line up. It is the reverse of the Einstein–de Haas effect, and gave g ≈ 2 for iron.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eM ∝ Ω\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eM: magnetisation (A\/m)\u003c\/li\u003e\n\u003cli\u003eΩ: angular speed of rotation (rad\/s)\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eThe equivalent field is B = Ω\/γ, with γ the gyromagnetic ratio; it is tiny at practical speeds.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e The proportionality holds for small Ω, and the effect is easily masked by Earth's field.\u003c\/p\u003e\u003ch3\u003eOn the sticker\u003c\/h3\u003e\u003cp\u003eBarnetta grips a spinning rod wrapped in glowing cyan rings. Printed text: \u003cstrong\u003eBARNETTA\u003c\/strong\u003e with the line \u003cstrong\u003eM ∝ Ω\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":50964288766055,"sku":"54749446973818032514","price":4.99,"currency_code":"USD","in_stock":true},{"title":"3\" × 3\" \/ White","offer_id":50964288798823,"sku":"45960400768556555679","price":6.99,"currency_code":"USD","in_stock":true},{"title":"4\" × 4\" \/ White","offer_id":50964288831591,"sku":"10423444667295915568","price":8.99,"currency_code":"USD","in_stock":true},{"title":"6\" × 6\" \/ White","offer_id":50964288864359,"sku":"87014530981402957140","price":11.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/12240979351210106718_1200.jpg?v=1793664618","url":"https:\/\/pixelatedphysics.com\/ko\/products\/barnetta-barnett-effect","provider":"Pixelated Physics","version":"1.0","type":"link"}