Date: Fri Feb 29 15:57:55 2008 Back to Contents

Author: Gerald Zani

Subject: Re: Tydall's Apparatus

Post:
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Cliff,

In truth and fairness it is not the true Tyndal apparatus. It is a simplification of the Tyndal device and it works better for a demo. The principle is the same and my faculty like it a lot.

The balls do not melt entirely through the wax. The balls are not hollowed correctly and do not have the same masses. The balls have the same volume. They melt into wax, not through it.

It is more reliable and easily repeatable.

http://www.physics.brown.edu/physics/demopages/Demo/thermo/demo/4b1030.htm

-- JZ

At 02:49 PM 2/29/2008, you wrote:
>Jerry,
>
>Do you have a picture for me of it? I am having trouble figuring out
>how the histoical apparatus I have could ever have worked as claimed
>unless you get the wax just right and are very careful about getting
>the temperatures the same. I still haven't figured out the discrepancy
>in the specific heats given in the original instructions (the only
>alloy is the brass sample, Dale). The first time I tried it, the
>copper sample won then came iron the second time iron won then copper
>then zinc. I used 1/4 inch thick wax sheets. Dale's version is a bit
>different in that he uses equal mass samples (BTW Dale, nice looking
>set up! I may steal it)
>
>Cliff
>
>Quoting "Zani, Gerald" :
>
>>Cliff,
>>
>>My faculty are absolutey thrilled with the Tyndall demo and would
>>never even consider to teach the intro stat mech thermo class
>>without it!
>>
>>No, no... not the archive, please.
>>
>>not banishment to the island of misfit demos! -- JZ
>>
>>________________________________
>>
>>From: tap-l-owner@lists.ncsu.edu on behalf of cbettis@unlserve.unl.edu
>>Sent: Fri 2/29/2008 12:32 PM
>>To: tap-l@lists.ncsu.edu
>>Subject: Re: [tap-l] Tydall's Apparatus
>>
>>
>>
>>I tried it a couple of times and decided it was not repeatable enough.
>>Besides, it isn't completely obvious that the balls should melt
>>through in the order of their specific heats as conductivity should
>>also play a role. So I'm putting it in the museum.
>>
>>Cliff
>>
>>Quoting cbettis@unlserve.unl.edu:
>>
>>>I am organizing my shelves in anticipation of a move to a new building
>>>(requests for bids were just released), so I've been evaluating the
>>>stuff I have as I go along. One of the things I found that hadn't been
>>>used in a while (perhaps with good reason?) was Tyndall's Apparatus for
>>>demonstrating specific heat. You take balls of iron, zinc, copper brass
>>>and lead, heat them in boiling water and then drop them on a paraffin
>>>sheet, the idea being that they should melt through in the order of
>>>their specific heats. My question is this: in checking up on the
>>>documentation I find a puzzle: the original instructions give the
>>>specific heats as: 0.119, 0.095, 0.094, 0.092, 0.031 kcal/kg ?C. When I
>>>look in current references I find: 0.11, 0.0925, 0.0923, 0.092, 0.031
>>>kcal/kg ?C (Tipler 4th edition). Does anyone know what's going on? I
>>>find it hard to believe that they didn't do accurate calorimetry in the
>>>old days. Obviously the differen values would have an impact on the
>>>demonstration which I am going to try later today. Maybe I should just
>>>restrict it to iron copper and lead.
>>>
>>>Cliff
>>
>>
>>
>>
>>
>>
>
>
>
>

Gerald Zani e-mail: Gerald_Zani@brown.edu
Manager of Demonstrations phone: (401) 863-3964
Department of Physics FAX: (401) 863-2024
Brown University Providence, RI 02912-1843 USA

URL http://www.physics.brown.edu/physics/userpages/staff/Gerald_Zani/index.html
URL http://www.physics.brown.edu/physics/demopages/demo/


"Eurika!"

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Cliff,
In truth and fairness it is not the true Tyndal apparatus. It is a
simplification of the Tyndal device and it works better for a demo.
The principle is the same and my faculty like it a lot.
The balls do not melt entirely through the wax. The balls are not
hollowed correctly and do not have the same masses. The balls have
the same volume. They melt into wax, not through it.
It is more reliable and easily repeatable.
http://www.physics.brown.edu/physics/demopages/Demo/thermo/demo/4b1030.htm

-- JZ
At 02:49 PM 2/29/2008, you wrote:
Jerry,
Do you have a picture for me of it? I am having trouble figuring out
how the histoical apparatus I have could ever have worked as claimed
unless you get the wax just right and are very careful about getting
the temperatures the same. I still haven't figured out the discrepancy
in the specific heats given in the original instructions (the only
alloy is the brass sample, Dale). The first time I tried it, the
copper sample won then came iron the second time iron won then copper
then zinc. I used 1/4 inch thick wax sheets. Dale's version is a bit
different in that he uses equal mass samples (BTW Dale, nice looking
set up! I may steal it)
Cliff
Quoting "Zani, Gerald" :
Cliff,
My faculty are absolutey thrilled with the Tyndall demo and would
never even consider to teach the intro stat mech thermo class
without it!
No, no... not the archive, please.
not banishment to the island of misfit demos! -- JZ
________________________________
From: tap-l-owner@lists.ncsu.edu on behalf of cbettis@unlserve.unl.edu
Sent: Fri 2/29/2008 12:32 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] Tydall's Apparatus

I tried it a couple of times and decided it was not repeatable enough.
Besides, it isn't completely obvious that the balls should melt
through in the order of their specific heats as conductivity should
also play a role. So I'm putting it in the museum.
Cliff
Quoting cbettis@unlserve.unl.edu:
I am organizing my shelves in anticipation of a move to a new building
(requests for bids were just released), so I've been evaluating the
stuff I have as I go along. One of the things I found that hadn't been
used in a while (perhaps with good reason?) was Tyndall's Apparatus for
demonstrating specific heat. You take balls of iron, zinc, copper brass
and lead, heat them in boiling water and then drop them on a paraffin
sheet, the idea being that they should melt through in the order of
their specific heats. My question is this: in checking up on the
documentation I find a puzzle: the original instructions give the
specific heats as: 0.119, 0.095, 0.094, 0.092, 0.031 kcal/kg ?C. When I
look in current references I find: 0.11, 0.0925, 0.0923, 0.092, 0.031
kcal/kg ?C (Tipler 4th edition). Does anyone know what's going on? I
find it hard to believe that they didn't do accurate calorimetry in the
old days. Obviously the differen values would have an impact on the
demonstration which I am going to try later today. Maybe I should just
restrict it to iron copper and lead.
Cliff








Gerald Zani e-mail: Gerald_Zani@brown.edu
Manager of Demonstrations phone: (401) 863-3964
Department of Physics FAX: (401) 863-2024
Brown University Providence, RI 02912-1843 USA

URL http://www.physics.brown.edu/physics/userpages/staff/Gerald_Zani/index.html
URL http://www.physics.brown.edu/physics/demopages/demo/

"Eurika!"



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From tap-l-owner@lists.ncsu.edu Fri Feb 29 15:57:55 2008

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