Re: [Phys-l] heat labs?

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

On Aug 25, 2007, at 10:38 AM, John Denker wrote:

> On 08/25/2007 10:09 AM, Kilmer, Skip wrote:
> > I do a similar lab, but run it twice: once in clear water and once in
> > water with black India ink powder. The first time most of the light
> > gets out, while most of the IR is absorbed. The second time both
> > light and IR are absorbed. It makes a good case against using
> > incandescent lamps for lighting. (although they are good heat
> > sources)
>
> Yes, the ink is a nice refinement.
>
> Beware that spilled or spattered India ink is exceedingly hard to
> get out of clothes, carpets, or any other porous items.  Many other
> dyes are less troublesome.  I like Easter-egg dyes, in part because
> they are considered safe for kids to handle.  Hint: stock up each
> year at the half-price after-Easter sale.
>
> I remark that you can do similar spectral calorimetry with sunlight,
> using various dyes, pigments, and colored objects in the water, and
> various colored filters in series with the light. However, I don't 
> really
> recommend this, because there are a gazillion things that can go wrong
> with it, and it's hard to do in a classroom setting.  (It might be
> workable on a take-home basis with relatively seasoned students, or
> as an unoriginal "science fair" project.)

A car light bulb, powered from a battery (or a power supply), would 
probably be more acceptable, from the legal point of view. Use the 
epoxy glue to make sure nothing electrical is in contact with water, or 
with students. This setup can be used to measure, not very accurately, 
latent heat of fusion.

_______________________________________________________
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/