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Re: [Phys-L] wikipedia (also electrophorus)



A neon bulb, patience and a good eye lets students see that the 'current' flows in opposite directions as the movable pie pan is charged and discharged with the styrofoam plate electrophorous.

The student holds one wire in their fingers and touches the other wire to the rim of the pie pan.

The pie pan first rests on the foam plate.
Touch the rim - see the flash.

Lift the pan - touch the rim - see the flash.

Then have them watch closely to see that it is the OPPOSITE electrode that flashes when the pan is up vs when the pan is down.

A bit of 'chemistry' convinces them that the flash is actually photons emitted when an electron 'falls' into the outer shell of the neon atom.
So we work out the sign charge that is on the surface of the foam electrophorus.


On Feb 25, 2013, at 12:44 AM, John Denker <jsd@av8n.com> wrote:

On 02/24/2013 10:37 PM, Chuck Britton wrote:
Can the WikiPedia article be improved?
Or is it more valuables as an object of derision?

The problem is that wikipedia is a moving target. This is a
lose/lose situation:
-- If you fix it, it might not stay fixed.
-- If you try to use it as an object of derision, it might
not stay broken.
<snip>
=================

As for the electrophorus topic: The following is a work in
progress. Right now it is about half finished:
http://www.av8n.com/physics/electrophorus.htm

IMHO it provides a good example of a real-world open-ended
question. Suppose somebody asks you what is an electrophorus,
and how does it work? By googling you can get a rough description
of its structure and general method of operation, but the explanation
of how it works is obviously bogus. So you start to wonder, how
does the thing actually work? Are there perhaps some important
components and/or procedures that have not been mentioned? Is
there perhaps a modified version that works better and/or is
easier to explain? Etc. etc. etc.

My explanation is not finished, but you can see where it is
going. It is markedly different than most of the other alleged
explanations out there.

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