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Unit of permeability #3295
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Yes, if tools are able to do any reasonable unit-checking (which I believe most are) that is trivial. https://en.wikipedia.org/wiki/Vacuum_permeability uses both H/m and N/A2, and give reasonable explanations for both, and also indicates a larger issue - the constant no longer has a fixed simple value, but now seems to be 4π × 1.000 000 000 82 (20) 1e-7. I can make a PR. (Just changing the value, not adding the indirect definition, since that definition requires yet another measured constant that I don't see any libraries using.)
That would work as well, but it depends on how dependent we want to make the libraries. |
Have made PR with the correct value, now it is just a matter of fixing the bad value on Wikipedia! |
I meant changing it from 4π × 1.000 000 000 82 (20) 1e-7 to 4π × 1.000 000 000 55 (15) 1e-7; as given in https://physics.nist.gov/cuu/pdf/all.pdf |
Reading more I'm not sure if we should change the type of the constant, as there are some indications that mu_0 isn't seen as "permeability of vacuum" anymore, but as a "magnetic constant". https://en.wikipedia.org/wiki/Vacuum_permeability I don't know if there is a deep reason for that (and if so what it is), but assuming there is it seems odd to use the type "Permeability". On the other hand https://physics.nist.gov/cuu/Constants/codata.pdf uses "magnetic constant" and mu/mu_0 as a relative permeability - indicating that mu_0 is also a permeability. |
In fact mu_0 is a permeability ... and I prefer unit = V.s/(A.m) |
Two questions:
SIunits.Permeability mu_0
instead ofReal mu_0(unit="N/A2")
?The text was updated successfully, but these errors were encountered: