Re: Oersted to Gauss; Conversion Factors

["H.B. Knowles" <hbknowles@hbknowles.com>]

At 15:32 05/11/2000 -0500, you wrote:
> Folks,
>
> I have a dilemma with the documentation for a tape 
> demagnitizer.
>
> The unit's magnetic output is rated in "oersteds."  I
> thought these would be easily converted to "gauss," but 
> it seems that the units do not measure the same 
> quantities, and they do not appear to be easily converted 
> one to the other.
>
> Is there a conversion formula for the two units?  Barring 
> that, is there a thumb rule that relates the two 
> quantities?
>
> Thanks,
>
> Jim Barnes, CHP
> Radiation Safety Officer
> Rocketdyne/Boeing
> james.g.barnes@att.net
Mr. Barnes:
There is in fact NO difference,  in terms of  physical
dimensionality, between the Gauss and the Oersted (capitalized: they are
peoples' names). They are from the electromagnetic  system of
units, in which- as always - B (bold, vector) is the magnetic
induction -also the magnetic flux per unit area, as stated elsewhere-
and H  is the magnetic field. (Often, B
is incorrectly called the "field)". In linear
materials  B =  (mu) x H, ( mu = permeability) . Mu is
dimensionless  in the electromagnetic system and  equal to
1.0000 in vacuum, and almost the same in air. These elecromagnetic units
are the same as in the Gaissian system of units, which unifies the
electromagnetic system with the electrostatic system.

The Oersted was really introduced because  people wanted to
differentiate between the induction and the field (in metals) and they
were using the Gauss as the same unit of both. This happened only about
1940.

Both differ from the more familiar MKSA system whic his based in the
meter-kilogram- second (SI) system, and in  which the B  is
measured in Tesla and the H in Ampere-turns per meter.

Give my not-very fond regards to Santa Sue.

Sincerely,

"Brook" Knowles

H.B. Knowles, PhD, Physics Consulting

4030 Hillcrest Rd, El Sobrante, CA 94803

Phone (510)758-5449

Fax (510) 758-5508

hbknowls@ix.netcom.com (until 1/31/00)

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