[Phys-l] A scaling quiz. Was: Re: thoughts for future physics regents.

[Bernard Cleyet <bernardcleyet@redshift.com>]

On 2011, Jun 22, , at 10:57, John Denker wrote:

> As I have mentioned before, units and dimensions are part of a
> larger topic, namely scaling.  (Every dimensional argument is
> also a scaling argument, but not vice versa: there is such a
> thing as non-dimensional scaling, but we don't need to get into
> that just now.)
>
> Scaling laws have been part of physics since Day One of modern
> science (1638) ... and are still important:
>    http://www.google.com/search?q=scaling+site%3Anobelprize.org
>
> Scaling is not mentioned on the typical syllabus, but IMHO it
> should be taught anyway.  It is *easier* than most of the stuff
> that is on the syllabus, and more age-appropriate ... and it is
> treeemendously powerful.


Three wires of vastly differing diameters, but the same resistivity, and length are connected in parallel and powered by a suitable P/S (e.g. high cap. lead-acid batt.)

Which will burn out first?

Hint:  re-read the subject line.

bc thanks Bill Layton for demonstrating this at the recent SoCAlPhys.Tech.Assoc. mtng. (SCPTA)

http://parallax.sci.csupomona.edu/scpta_blog/


p.s. he used nichrome wires, so one just glowed instead of fusing.

p.p.s. I think Bill said this was a Sutton demo.


http://physicslearning.colorado.edu/PiraHome/Sutton/Sutton.htm

And finally:  an advanced prob. is to determine the equilibrium temp. of each.  (involves; still air, orientation, emissivity, resistance, power consumed, radiant flux, etc.  most as a function of temperature)