主题：【原创】基本单位之间的关系 -- 橡树村

后来发现这个基准并不准确地等于1立方分米最大密度纯水的质量，而是等于1.000028立方分米的水的质量。于是在1875年米制公约会议之后，也用含铂90%、铱10%的合金制成千克原器，一共做了三个，经与巴黎档案局保存的铂质千克原器比对，选定其中之一作为国际千克原器。这个国际千克原器被国际计量局的专家们非常仔细地保存在特殊的地点，用三层玻璃罩好，最外一层玻璃罩里抽成半真空，以防空气和杂质进入。随后又复制了四十个铂铱合金圆柱体，经过与国际千克原器比对后，分发给各会员国作为国家基准。跟米原器一样，千克原器也要进行周期性的检定，以确保质量基准的稳定可靠

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鲜花已经成功送出。

此次送花为【有效送花赞扬，涨乐善、声望】

Since a coulomb is approximately equal to 6.24150948×10^18 elementary charges, one ampere is approximately equivalent to 6.24150948×10^18 elementary charges, such as electrons, moving past a boundary in one second.

As with other SI base units, there have been proposals to redefine the kilogram in such a way as to define some presently measured physical constants to fixed values. One proposed definition of the kilogram is:

“ The kilogram is the mass which would be accelerated at precisely 2×10^-7 m/s^2 if subjected to the per metre force between two straight parallel conductors of infinite length, of negligible circular cross section, placed 1 metre apart in vacuum, through which flow a constant current of exactly 6 241 509 479 607 717 888 elementary charges per second. ”

This redefinition of the kilogram has the effect of fixing the elementary charge to be e = 1.60217653×10^-19 C and would result in a functionally equivalent definition for the coulomb as being the sum of exactly 6 241 509 479 607 717 888 elementary charges and the ampere as being the electrical current of exactly 6 241 509 479 607 717 888 elementary charges per second. This is consistent with the current 2002 CODATA value for the elementary charge which is 1.60217653×10^-19 ± 0.00000014×10^-19 C.