Re: [Phys-L] Temperature for the calorie?

[Richard Tarara <rtarara@saintmarys.edu>]

There is also the BTU--which is very prevalent in the heating and 
air-conditioning industry and which is still used in global energy 
estimates (quads).  With the textbook definition as the amount of energy 
to raise one pound of water by one degree Fahrenheit is surely is 
closely related to the calorie.

Having taught introductory physics (and only introductory physics) for 
35+ years, I can offer that at very least at the non-scientist course 
level, having a unit that is simple to remember ( one!) that is related 
to something that is physical and easily understood (heating water) 
offers some advantages.  Then one can add in the more universal 
conversion factor.  These students do worry about Calories (even before 
they have the tools to understand) and being a kcal is easier for them 
to handle than 4184 Joules.  While clear enough to us, the Joule is not 
a very intuitive unit of measure for most.  In the same vein, then 
simple calorimetry (like the latent heats for water) have more easily 
remembered (approximately) values (~80 cal/g or ~540 cal/g) for 
discussions in these lower level classes.  As always, one needs to take 
the audience into consideration.

rwt

On 1/28/2016 7:36 AM, John Denker wrote:
> On 01/27/2016 09:13 PM, I wrote:
>
> > Nobody in their right mind uses calories
> By that I meant small calories.  Obviously big Calories are still in
> use for food labels at present ... but even so, the FAO recommends
> gradually transitioning to joules.
>    http://www.fao.org/docrep/meeting/009/ae906e/ae906e17.htm
>
> That report makes sense to me.  It also says:

--
Richard Tarara
Professor Emeritus
Saint Mary's College

free Physics educational software
http://sites.saintmarys.edu/~rtarara/software.html