Re: [Phys-l] para/dia-magnetism

[brian whatcott <betwys1@sbcglobal.net>]

On 4/19/2011 11:59 AM, Carl Mungan wrote:
> /snip/
> My question is why the prefixes "para" and "dia" for magnetism?
>
> I'm okay with the idea of a paramagnet as one in which the induced
> magnetic dipole moment u is PARAllel to the external magnetic field B.
>
> Great, but why the term diamagnet for the case in which u is opposite to B?
>
> In particular, what connection (if any) is there to the terms
> "dielectric" (for which the induced electric dipole moment p is
> parallel to the external electric field E) and "diathermal" (which is
> a material which allows the flow of heat readily, as opposed to
> "adiathermal").
/snip/

I notice that Faraday put some effort into classifying magnetic materials.
He was uncomfortable with Becquerel's position that materials could be
 place on a list of increasing magnetic orientation in the axial direction
between magnetic poles.
Faraday showed that with a strong magnetic force (a horseshoe electromagnet
capable of lifting 50 pounds weight of magnetic material on either pole.)
he could show a transverse (what he called equatorial) orientation of 
materials.
He decided that these materials would be called diamagnetic, as opposed to
the usual label "magnetic" for those showing attraction or normal 
orientation.

He distinguished effects caused by inhomogeneity of the field from those
 present in uniform fields.
It has stayed with me that he checked the action of beef - which he 
expected,
 from the presence of iron compounds which are usually magnetic in any
chemical condition and which reversed his supposition.

Brian W