Re: e-field software?

[gastineau@badgerden.com (John E. Gastineau)]

On 31 Jan 97 at 22:50, Leigh Palmer wrote:

> > Does anybody know of a piece of shareware or freeware software for
> > the Macintosh that will graphically show e-field lines for various
> > setups? I've tried the usual sources like AOL and
> > www.shareware.com with no luck.
>  
> Today in lecture someone asked me to draw a few more magnetic field
> lines on the diagram I was making (two wires carrying parallel
> currents coming straight out at you). I was sufficiently unconfident
> of my ability to produce such a drawing without seriously misleading
> them that I declined to do so, stating that reason. What is needed,
> of course, is a program which will allow one to draw many more field
> lines than are usually drawn in the figures that appear in
> textbooks.

There are several Mac (and PC) programs which will do just what you 
want, but they're not free. 

First and most important (based on my teaching) is EM Field by Bruce 
Sherwood and David Trowbridge. (DT wrote Graphs and Tracks, another 
important program, and BS is the author of cT.) EMField will let you 
drop point charges of various signs and magnitudes anywhere on the 
screen. Then you can request field lines, equipotential lines, field 
directional vectors, field intensity vectors, and potentials at 
points. You can also drag the charges around, and see all your 
"measurements" respond. You can then move to end-on views of infinite 
charged rods, and do their field lines, as well as flux and Gauss's 
Law. The presentation of Gauss's Law is great, and I can't imagine 
teaching e&m without it. Again, everything is live; you can drag 
things around and see it all change. You can also use 
current-carrying rods and do magnetic fields. 

I wrote a review of EMField for the Physics Courseware Communicator 
(wow--I just looked for the date--Autumn '93, eons ago) but it was 
pretty short. I suggest getting a copy to play with. Anyway, I've 
been teaching with this for some time. Great package. 

Another good package, though a little more specialized, is Electric 
Field Hockey. It's a game, yes, but you can link up dynamics with 
electric fields and the concept of superposition. Student enjoy it, 
but there's enough good physics there that you can even frame very 
nice homework and exam questions based on it. EFH was written by 
Ruth Chabay. There are some HW problems using EFH in the 
Chabay/Sherwood E&M text, which long-time phys-l readers will have 
seen me rave about. 

A final program is Electric Field Plotter by Bob Nelson. I'm not as 
fond of this one, and have not taught with it. However, it will do 
more automated plots of fields than EM Field.  

All of these work well both in a lecture-demo mode as well as for 
individual student work.

All three of these packages are Physics Academic Software titles
(pas@aip.org). 

Usual disclaimers--I don't (and never have) worked for PAS, despite 
what some think!

Leigh mentioned Blas Cabrerra's electric field program. I  remember 
that one, and used to use it way back when. Kinko's doesn't 
distribute those any more; Intellimation does. The Cabrerra program 
is incredibly slow and not at all interactive, so while it was 
excellent in its day, I can't recommend it. 

JEG

--
John E. Gastineau                (304) 296-1966
900 B Ridgeway Ave.              gastineau@badgerden.com
Morgantown, WV 26505
http://www.badgerden.com/~gastineau