Re: On 1/4*Pi in Coulomb's law

[Doug Craigen <dcc@ESCAPE.CA>]

Ludwik Kowalski wrote:
> Let me say that these good observations would not be
> meaningful to students in the first physics course who
> do not know what the laplacian or the delta function is.

Yes, John Denker was addressing something much different than you, or
than what I was addressing.  However, his point is an elaboration on
part of what I said, the 4pi is due to the math - it will arise in some
of your EM equations no matter what you do with the units.  I say,
rather than try to avoid it, give the students a sense of why it is
there in whatever equation it arises in the unit system you are using.
I don't see it being an issue that it arises in Coulomb's Law as opposed
to some other equation.

In the SI system Coulomb's law does not seem to me the natural starting
point, Gauss' Law is.  There we have a simple proportionality between
sources (charge) and the resulting field.
Coulombs law as F=qE = q1*(1/e_o)*(q2/area) where the area is 4pi*r^2 is
a perfectly natural consequence of this approach and from the point of
view of teaching basic physics I like the fact that it leads naturally
to some unifying concepts that most people seem to miss in introductory
physics.

\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\

Doug Craigen
          http://www.dctech.com/physics/about_dc.html