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Re: GAUSS LAW



PHYS-L@lists.nau.edu writes:
The terms "lines flowing into the box" and "lines flowing
out of the box" were invented to promote discussion, and
to emphasize that nothing is really flowing unless sources
or sinks of E become sources or sinks of v fields.
Ludwik Kowalski

Yes, this emphasis is very important -- together with the teaching that a
"field" is a mathematical invention and really doesn't exist -- and that
lines are an even more remote invention and do not exist.

I am plannign on a flux ontro tomorrow. It is such an abstract idea! I try
this analogy and seek your wisdom.

I use a small bulb halogen flashlight and a beaker. I ask for acceptance
of the idea of light rays passing through the glass for cases of bulb
outside the glass, inside the beaker and then the black end in the beaker.
I would argue that light rays are only a little more real than field lines
and a whole lot more "visible"

I also use the overhead rays and a loop to tlak about flux and angle
between surface and lines.

I believe the transition to field lines is easy and when I have used this
in the past, my students act like they understand.

Is this a bad analogy? I try to avound the flow word and have rays
penetrate.....

Ken Fox
AP/IB Physics Teacher
Smoky Hill High School
Aurora, CO