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Re: Oersted to Gauss; Conversion Factors



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 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)
hbknowles@hbknowles.com (new)
<www.hbknowles.com>