{"product_id":"kibbla-kibble-balance","title":"Kibbla – Kibble Balance \/ The Kilogram from Planck's Constant Physics Sticker","description":"\u003cp\u003eKibbla, a gold balance-paladin of The SI Guard, holds the beam of a Kibble balance level and weighs the kilogram with electricity.\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eA Kibble balance runs in two modes. In weighing mode, a current I in a coil sitting in a radial magnetic field pushes up with force BLI, balancing the weight mg. In moving mode, the same coil is moved at speed v and a voltage U = BLv is induced. The hard-to-measure product BL cancels between the two, leaving a match between mechanical and electrical power.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003emgv = UI\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003em: test mass (kg)\u003c\/li\u003e\n\u003cli\u003eg: local gravitational acceleration (m\/s²)\u003c\/li\u003e\n\u003cli\u003ev: coil velocity (m\/s)\u003c\/li\u003e\n\u003cli\u003eU: induced voltage (V)\u003c\/li\u003e\n\u003cli\u003eI: coil current (A)\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eU and I are measured with the Josephson and quantum Hall effects, whose constants are K\u003csub\u003eJ\u003c\/sub\u003e = 2e\/h and R\u003csub\u003eK\u003c\/sub\u003e = h\/e². Since 20 May 2019 the SI fixes h = 6.626 070 15 × 10⁻³⁴ J s exactly (with e also exact), so the balance turns the fixed value of h into a mass. The platinum-iridium prototype Le Grand K is no longer the definition.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e The equation is “virtual power”. The two modes run at different times, so no power actually flows; mgv = UI is a comparison, not an energy transfer. g and v must also be measured, with an absolute gravimeter and laser interferometry.\u003c\/p\u003e\u003ch3\u003eOn the sticker\u003c\/h3\u003e\u003cp\u003eKibbla holds the polished 1 kg mass in one hand and the glowing coil in the other. Printed text: \u003cstrong\u003eKIBBLA\u003c\/strong\u003e with the line \u003cstrong\u003emgv = UI\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":50962767478887,"sku":"10607539501928831366","price":4.99,"currency_code":"USD","in_stock":true},{"title":"3\" × 3\" \/ White","offer_id":50962767511655,"sku":"97466531543652282426","price":6.99,"currency_code":"USD","in_stock":true},{"title":"4\" × 4\" \/ White","offer_id":50962767544423,"sku":"22075112716549840863","price":8.99,"currency_code":"USD","in_stock":true},{"title":"6\" × 6\" \/ White","offer_id":50962767577191,"sku":"73687459534708115617","price":11.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/8427099523694371239_1200.jpg?v=1793664639","url":"https:\/\/pixelatedphysics.com\/ja\/products\/kibbla-kibble-balance","provider":"Pixelated Physics","version":"1.0","type":"link"}