ARRELL: E&M are not new. Agreed! But my statement was true, I assume?
ARRELL wrote:
Michael Gmirkin wrote:Are Wikipedia, the Hyperphysics site, the World Health Organization site and the NASA educational site I quoted in the original message, which all appear to agree with each other, correct in assessing that magnetic fields arise from electric currents?
You act as if you are stating something new here. You are not.
That didn't exactly answer the question. But I'll take the implication to be that you agree magnetic fields track back to electric currents. A simple yes or no will suffice.
Likewise, I assume that you would agree that magnetic field strength is proportional to current strength and "field line" topology (a visualization tool, not a reified entity) is dependent on electric current geometry? Again, a yes or no will suffice.
If yes on the above points, can magnetic fields be used to "diagnose" electric currents, as implied in the Wikipedia article?
Electric current can be directly measured with a galvanometer, but this method involves breaking the circuit, which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field associated with the current.
Again, a simple yes or no answer will suffice.
Further, if yes, is it permissible to conclude deductively that where magnetic fields are observed, an electrical current must exist somewhere to generate them?
With regards to "newness," I don't think I've ever claimed that the relationship between E&M fields or between magnetic fields and electric currents were new concepts (I've pointed out the primacy of Maxwellian thought, Ampèrian though and the thoughts of Faraday and Gauss, and that they've been well-known for some time!).
My point is and more-or-less has been that the relationship is often not tacitly acknowledged (of late) and in some cases may be improperly applied or "over-simplified," to the detriment of theoretical understanding. Moreover it appears to be verboten to even mention electric forces in the discussion of astronomy without some kind of a hand-waving, reactionary, knee-jerk reaction ensuing.
Regards,
~Michael Gmirkin