Re: [Phys-L] Names

[John Denker <jsd@av8n.com>]

On 06/19/2012 12:49 PM, Aburr@aol.com wrote:
> In the subject of elementary electrostatics, what names do you give to  E 
> and D

E is the electric field ... also known as the E-field.
Similarly, B is the magnetic field ... aka the B-field.

In the /elementary/ course, I don't go anywhere near D or H.
That's because E and B are fundamental physical concepts (in
the static limit) ... whereas D and H depend on approximations 
and assumptions about "continuous media", and don't even exist 
in the general case.

In some non-elementary situations it is convenient to talk about 
the H-field.  For example, it is common to talk about magnetic 
hysteresis in terms of the "B versus H" curve.

I suppose there must be analogous practical applications for the
D-field, although I can't think of any.

At the moment I know what to call D and H _because I just looked it up_
but I will have forgotten by tomorrow.  Mostly I just call them the 
D-field and the H-field ... although I usually don't talk about D 
at all.  I can't remember any situations where writing D was more 
convenient than writing εE ... although I suppose such situations 
must exist somewhere.

To save you the trouble of looking it up:
  D is the "electric displacement"
  H is the "magnetizing field"
although you can have a long and happy life (and a career in physics)
without needing to know either of those names.  Don't ask me to explain 
where either of those names came from;  AFAICT they're not particularly 
descriptive.