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Re: [Phys-l] Which one is positive?



Other methods are to use thermionic emission and the photo-electric effect. These will serve as a polarization detectors. However, I suspect the original method to define was the triboelectric effect, which was used to label the anode and K in early primary electro-chemical cells.

bc thinks no c. britton problem w/ primary cells.


On 2010, Jun 17, , at 06:37, chuck britton wrote:

Your question was - which terminal is POSITIVE.
The chemist is confusing you by using the words anode & cathode.
These words are NOT synonymous with Pos & Neg.

Shun the words anode & cathode like the plague.
They apply to oxidation and reduction reactions NOT to positive and
negative electrodes.

As you drive your car, the battery anode and cathode swap back and forth.
The positive terminal stays fixed.

(and personally, I have much more access to meters, LED's and
other such indicators than I do platinum and silver electrodes.)

At 9:22 AM -0400 6/17/10, ludwik kowalski wrote:
Suppose you have a low voltage dc power supply whose terminals look
alike. How to find out which one is positive? Here is one
suggestion, made by chemist.

"A good test for the proper connection is to use a silver wire anode
and a platinum wire cathode in a sodium chloride solution. When
current is passed, you should see an insoluble white precipitate of
AgCl forming at the silver anode. If you don't see this, then your
cell is connected backwards."

I did not know this.


Ludwik

http://csam.montclair.edu/~kowalski/life/intro.html



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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l