Re: [Phys-l] teaching energy

[John Denker <jsd@av8n.com>]

On 10/03/2006 02:04 PM, Rauber, Joel wrote:

> Consider three point charges at the corners of a triangle, do you think
> a student (or even a professor) will have an easier time calculating the
> PE using a field concept or an interaction concept?

That's an instructive example ... but not the whole story.

Suppose I have three charges at the corners of a triangle, *plus*
a piece of dielectric a little ways away.  I would calculate the
field due to the charges in the elementary way, *not* calculating
the PE of the charges themselves.  I would then square the field
and use field-energy arguments to estimate the force on the
dielectric.

The point is that I have used two methods in the same problem:
The first step did not use field energy, while the second step
did.

"Let many flowers bloom."