Re: [Phys-l] battery redux and again (part deux)

[fizix29@aol.com]

Thanks!  I had already read your documents on av8n.com and will look at the updated versions, as well as the Feynman lectures. 
Justin Parke
Oakland Mills High School
Columbia, MD
 
 
-----Original Message-----
From: jsd@av8n.com
To: phys-l@carnot.physics.buffalo.edu
Sent: Wed, 28 Feb 2007 10:16 PM
Subject: Re: [Phys-l] battery redux and again (part deux)


On 02/28/2007 02:05 PM, fizix29@aol.com wrote:

> My question is simply what is the mechanism in a real chemical battery which 
transports the
> charge against the electric field?

1) The microscopic mechanisms inside batteries are insanely complicated
  and tricky.  Really understanding it would probably be a tour-de-force
  of chemistry and condensed-matter physics.

  I say "probably" because I've never seen it done.

  Here are some modest efforts of mine, which say a few things about
  the structure and strategy of batteries ... but which may leave you
  with as many questions as answers:
    http://www.av8n.com/physics/battery.htm
    http://www.av8n.com/physics/lead-acid.htm

  This afternoon I revised the "battery" document and greatly upgraded
  the figures.

  All the gen-ed textbook discussions I've seen are provably nowhere
  close to being correct.  For starters, most of them show the electric
  field in the middle of the electrolyte compartment going the wrong way.

  I've read some of the engineering literature, and it has remarkably
  little to say about the microscopics.

2) It is amusing in a macabre way to read the textbook "mechanical"
  analogies of how a battery works, based on VdG generators and such.

  One big problem is that most students have no clue about the microscopic
  phenomena involved in static electricity.  Therefore the any such
  mechanical model of a battery contravenes the rule that "learning
  proceeds from the known to the unknown".

  As a pedagogical suggestion, I would suggest figuring out how
  electrostatic generators work ... not because they directly
  provide a good model for batteries -- which they don't -- but they
  are interesting unto themselves, and they lay some useful general
  groundwork concerning work functions, dipole layers, and suchlike.

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