Re: [Phys-l] Wire through ice experiment

[Ludwik Kowalski <kowalskil@mail.montclair.edu>]

On Aug 10, 2007, at 3:57 PM, Richard Hake wrote:

> Antti Savinainen (2007) in his Phys-L post of 9 Aug 2007 titled "Wire
> through ice experiment," wrote [my insert at ". . .  .[insert]. . .
> .":
>
> "The work . . . . .[Valjus (2006]. . . . contains an interesting
> result regarding wire through  ice experiment: it seems that thermal
> conductivity plays a significant role in it instead of depressing of
> freezing point  due to pressure. Take a look if you are interested:
> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
>   It would be interesting to hear your comments."
>
> There's an analysis of rate at which a weighted steel bar moves
> downward through a block of ice in my ancient thermo text [Zemansky
> (1951)], indicating that the rate is directly proportional to the
> "over-all heat transfer coefficient of the composite heat conducting
> path consisting of the metal and the water layer."
>
> I used to do a demo in which two apparently identical copper wires
> (about 0.010 inches in diameter) were loaded at the ends with
> identical weights and placed over identical ice cubes ran a
> regelation race through the ice cubes. The two set ups were viewed at
> close range by several students who verified that they appeared
> identical.
>
> As I recall one of the wires took about 10 times longer to pass
> through the ice than the other,  to the surprise of the few students
> who were still awake.
>
> No one ever guessed the reason - before the demo one of the wires had
> been soaked in hydrofluoric acid to remove its very thin insulation
> layer and thereby drastically increase its over-all heat transfer
> coefficient.

Another way to demonstrate this is to compare a copper wire and a 
fishing-road "wire" (nylon) of the same diameter. If Zemansky's 
explanation is correct then times to go through the ice block should be 
about the same for both wires.

1) It is a great opportunity to show students how a reasonable 
explanation can be debunked by a clever experiment.

2) Did Zemansky believe the explanation or did he use it because it was 
reasonable?

3) Did physicist of Fayman generation believe in this explanation?
_______________________________________________________
Ludwik Kowalski, a retired physicist
5 Horizon Road, apt. 2702, Fort Lee, NJ, 07024, USA
Also an amateur journalist at http://csam.montclair.edu/~kowalski/cf/