[FRIAM] Naïve physics question

[Robert J. Cordingley]

Seems like from a thermodynamics question you can first think of having 
two identical systems with identical energy inputs. Unless one of the 
systems is capable of storing energy in some form differently from the 
other the equilibrium temperatures should be the same.

Now CFBs emit more of the their input energy as light which since the 
containers are transparent (presumably to the same light that's emitted, 
visible, UV, infrared) it will escape more easily. Incandescents 
generate a lot of heat for the same energy input which may not escape as 
easily as the light energy. It will depend on the thermal conductivity 
of the container's materials etc. If the CFB were 100% efficient all 
it's energy will leave immediately in a container that is 100 % 
transparent to its 'light' and show no temperature increase. If the 
incandescent's heat is transmitted as infrared energy at 100% efficiency 
along with any light then its temperature will show no increase either.  
So the answer may have more to do with the properties of the containers 
than the properties of the lights. Practically, I'd expect A to warm up 
more than B because B's light energy will escape more easily with 
materials we are familiar with.

If both containers are opaque to all light (UV, visible and IR) and have 
the same thermal conductivity properties we are back to the first paragraph.

2c

Robert C


On 2/14/17 8:01 AM, Gary Schiltz wrote:
> Since there are some non-naïve, i.e. professional physicists, as well 
> as just gererally smart people in FRIAM, I pose the following fun 
> question. Given: two transparent, sealed containers filled with air - 
> one contains an incandescent light bulb A that consumes 100 watts of 
> energy; the other container contains a fluorescent light bulb B that 
> also *consumes* 100 watts of energy. Since B is of a more efficient 
> design, it will produce more light than A. Assuming the same color 
> temperature light is produced by A and B, and ignoring any feedback 
> effects of rising temperatures inside the respective containers, will 
> the temperatures inside the containers reach the same 
> temperature? Naïve physicist G (me) thinks that since more light is 
> escaping from the container containing B, that its temperature will 
> rise less. G also thinks that if the containers are opaque, that the 
> temperatures will rise by the same amount. But G is besieged with 
> doubts. Please help G.
>
>
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