[time-nuts] Primary Standards...

[Don Latham]

Gosh. I remember the ampere as the current that would deposit a given
weight of silver in a fixed time...

Also saw a note about one part in e-20. As the universe is apparently
about 5e17 sec old, can we make a standard that is good to 1 sec in 1e20
sec???
Don


Dr. David Kirkby
> David C. Partridge wrote:
>
>> No they cannot be - yet.  At the point where (e.g.) the second is
>> re-defined
>> in terms of the aluminium quantum clock, then the aluminium quantum
>> clocks
>> are then by definition the primary standards of time, and all the Cs
>> clocks
>> are now secondary standards as the second is no longer defined in terms
>> of
>> the Cs beam clock.
>>
>> Dave
>
> Does that mean that there is no primary standard for the Ampere?
>
> An Ampere is defined as the current which will produce an attractive force
> of 2
> × 10–7 newtons per metre of length between two straight, parallel
> conductors of
> infinite length and negligible circular cross section placed one metre
> apart in
> a vacuum.
>
> Since its impossible to build such a system, does that mean there is no
> primary
> standard for an amp?
>
>
>
> Dave
>
>
>
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-- 
Dr. Don Latham AJ7LL
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