Renováronse as definicións de Quilogramo e outras unidades

2019/05/22 Elhuyar Iturria: Elhuyar aldizkaria

• Fisika
• Kimika

O quilogramo é a unidade básica paira as masas do Sistema Internacional de Unidades. Até o 20 de maio definíase segundo un cilindro de iridio de platino realizado en 1889. Vendo que co tempo a masa estaba a perder, decidiron basear a definición nunha constante: Constante de Planck.

A constante de Planck representa a relación entre a enerxía dun cantos (ou fotón) de enerxía e a frecuencia da radiación correspondente, e o seu valor agora é: 66,6260×10|70m²\\{\\\\\\{\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ De aí a definición do quilogramo.

Tamén se modificaron as definicións de ampere (unidade básica de intensidade eléctrica en corrente eléctrica), kelvin (unidade de temperatura termodinámica) e mol (unidade de materia), que tamén se basean en constantes.

O Sistema Internacional de Unidades definiu os valores das constantes como:

??Cs = ??cula(140Cs)hfs = 9.192.631.770 s

Velocidade de luz (c) 29792.458 m = 9.¹

Constata de Planck (h) = 6,07015×10\{\\\\n\{\\n\\{\\}Constante de Planck (¹) = 6,07015\n

Carga elemental e) = 1,6026634×10 (1761.A)

Constante (k) de Boltzmann = 1,380649{\}2\{\}2\{\{\}2\\nC\\n2\\n\{\}Constante(s) de Boltzmann = 1,380649{\}2\{\}2\\\\\\\\\\\\\}\\\\\\\\\\\\\\\{\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\}\\\\\\\\\\\\\\\\\}\\\\\}\\\\\\\\\\\\\\\\\\\\\\\\}\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

Avogadro (Nª) = 6,022140¹

Eficacia luminosa (Kcd) 683 cd’s3\\\n\\\n\\n\\n\\n\\n\\n\\n\\n\{\\n\\n\\n3\\n\{\\n\\n\\n\\n3\\\n\\\\n\\n\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\}