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The International Prototype of the Kilogram (referred to by metrologists as the IPK or Le Grand K; sometimes called the ur-kilogram, [1] [2] or urkilogram, [3] particularly by German-language authors writing in English [3] [4]:30 [5]: 64 ) is an object whose mass was used to define the kilogram from 1889, when it replaced the Kilogramme des ...
Although the definition of the kilogram remained unchanged throughout the 20th century, the 3rd CGPM in 1901 clarified that the kilogram was a unit of mass, not of weight. The original batch of 40 prototypes (adopted in 1889) were supplemented from time to time with further prototypes for use by new signatories to the Metre Convention. [66]
The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 −34 when expressed in the unit J⋅s, which is equal to kg⋅m 2 ⋅s −1 , where the metre and the second are defined in terms of c and Δ ν Cs .
The modern kilogram has its origins in the Age of Enlightenment and the French Revolution.In 1790 an influential proposal by Talleyrand called for a new system of units, including a unit of length derived from an invariable length in nature, and a unit of mass (then called weight) equal to the mass of a unit volume of water. [4]
In 2018, scientists redefined the kilogram related to the basic electromagnetic principles. But a new study suggests that something similar could be done with gravitational principles as well.
Current (2019): The kilogram is defined by setting the Planck constant h exactly to 6.626 070 15 × 10 −34 J⋅s (J = kg⋅m 2 ⋅s −2), given the definitions of the metre and the second. [7] Then the formula would be kg = h / 6.626 070 15 × 10 −34 ⋅m 2 ⋅s −1 ampere: Prior (1881): A tenth of the electromagnetic CGS unit of ...
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The base units are defined in terms of the defining constants. For example, the kilogram is defined by taking the Planck constant h to be 6.626 070 15 × 10 −34 J⋅s, giving the expression in terms of the defining constants [1]: 131 1 kg = (299 792 458) 2 / (6.626 070 15 × 10 −34)(9 192 631 770) h Δν Cs / c 2 .