Date: Mon Apr 2 15:08:38 2007

Author: Erich Burton

Subject: Re: Visual Electricity Demonstrator

Post:

We have one of the Visual Electricity Demonstrators -- it is at least
seven years old. Ours shows current flow (as opposed to electron flow).
Unfortunately I do not seem to be able to locate the datasheet.

It seems to work as I would expect.

The write-up linked to your web site (P2-2600_DS.pdf) is confusing,
as you use "conventional current" and "electron flow" interchangeably,
and refer to the LEDs as representing "electrons", which is incorrect.

The device is quite useful, particularly for showing the magnitude and
direction of current in a circuit as a large capacitor is charged from a
battery and then, at the throw of a switch, discharged through a lamp
bulb.

If a professor asked to demonstrate electron flow, I would simply
flip over the device (leaving the external wiring intact).

-Erich


Cary Busby writes:
:I am requesting help from those of you who have Arbor Scientific's Visual
:Electricity Demonstrator (http://www.arborsci.com/detail.aspx?ID=532). I
:am on the staff at Arbor. I write and revise the product datasheets. A
:customer recently received the VED and connected it in a battery-powered
:circuit. He noticed that the lights appeared to flow from the positive
:battery terminal to the negative, and called us because he thought the
:lights were supposed to represent electron flow. He expected them to flow
:out of the negative terminal.
:
:We have tested the VED's in the warehouse, and they too flow from the
:positive. Since we rarely use this demo with batteries (we normally use it
:with Genecons), some of us are convinced that the VED's are working properly
:and the datasheet needs to be re-written. Others of us are convinced that
:the VED's are not being built properly, and are working backwards.
:
:If you have a VED, and have a few mintues, could you do me a favor and test
:it with a battery? Let me know, please, which direction the lights flow,
:and the approximate age of the VED. (If you have the instruction sheet, you
:can look at the copyright. It was last revised in 2001, and the product has
:been around for at least ten years.) Also, if we say that this demo models
:the flow of electrons in a wire, which direction would you EXPECT the lights
:to flow? (I know what I think, but it appears that I need backup to make my
:case.)

____________________________________
Erich Burton 3-2602 eburton@bu.edu
Boston University Physics Department

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