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

[Doug Craigen <dcc@ESCAPE.CA>]

Ludwik Kowalski wrote:
> But we do not teach physics this way in elementary courses.
> For us Coulomb's law is the starting point. Students know
> nothing about Gauss law at this time. Heaviside introduced
> 4*Pi into the Coulomb's law to make it disappear in the Gauss
> law. That was his main motivation; right? But how can one
> use this reasoning with somebody who does not know Gauss
> law? We do not. We say "accept the 4*Pi factor because it
> will benefit us in the future." That is how an element of
> apparent dogmatism is introduced. It is not a scientific
> topic, it is a pedagogical topic.

Admittedly I've only taught first year physics 4 times, but the text
begins with a recap of stuff they should be familiar - charging by
rubbing, opposites attract etc - and then begins the numerical part by
dropping Coulombs law in out of the blue.  Naturally the more
complicated it looks the harder it will be to memorize and the more
buttons they will have to push on their calculator, but my biggest
objection is that it is out of the blue after a series of observations
that establish the existence of "fields" which appear to have properties
such as:
- force is proportional to amount of charge times the field in which it
sits
- fields are generated proportional to the amount of charge in near
vicinity

I believe the flow to be strong enough to disregard the order in the
text, to introduce fields as something which they have already
experienced, and to lead into Coulomb's Law from there.


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

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