I agree with the others that you are trying to complicate that which is simple.
Naty1 said:
How do we KNOW a plain old electric heater is "100% efficient"?
According to the superficial logic of "energy conservation" posted above seems like one would also answer the same for incandescent and fluorescent bulbs as for resistors: all use electricity, all produce electromagnetic waves, all produce some visible light along with heat.
If the room is sealed and has no windows, all
are 100% efficient at producing heat.
Yet I believe fluorescent bulbs produce significantly more light than heat...so I think something is going regarding the conversion efficiency of electricity to electromagnetic radiation at different frequencies...seems maybe its more efficient at lower (infrared) frequencies? This is perhaps more a question of thermodynamics than EE...
All of the light emitted by a light bulb is absorbed by the walls and objects in the room and converted to plain, ordinary heat.
But perhaps you are looking for a different type of efficiency. You could divide light output in watts by energy input in watts and get "
light generating efficiency" (and you can, in fact, find light bulbs described this way), but that's not what you asked in the OP and not mutually exclusive with the fact that the
heat generating efficiency is 100%.
Why should tungston and nichrome, for example, be equally efficient?? I don't know because I don't know the exact process for converting electron flow into radiant energy.
Energy has to
go somewhere. If you take a box and keep putting energy into it, it will just get hotter and hotter and hotter without end. In order to avoid the paradox of a continuously increasing temeprature, the box must come to an equilibirum point where it releases - in whatever form - as much energy as is put into it.
But the "standard answer" "clearly doesn't distinguish between fluorescent and incandescent bulbs...so as of this moment I don't accept it as a valid response...if different processes yield different heat outputs (fluorescent vs incandescent, for example) how was it decided resistance is 100%?...
Again, this is just you overthinking it. Visible light, infrared, UV - these are all just different flavors of ice cream. They are all the same thing: radiant heat. As I said above, you can create another forumlua that describes the difference between visible light and ir light output and call it a different kind of efficiency, but that doesn't mean the
heat generation efficiency of any of these devices is anything other than 100%.
what I was starting with was the idea that perhaps, for example, resistance heating materials are chosen for partly their longevity rather than only heat producing efficiency...tungesten filaments in a vacuum were chosen after other materials and fabrications burned up...hence I'm asking if there is an opportunity...and nichrome may be the toaster material because while more expnsive, it doesn't burn up in air.
Correct: materials are chosen mostly for their durability (and that includes the operating temperature, since the operating temperature determines the light color and light producing efficiency).
As another example, microwave ovens also provide heating: more or less efficient than resistance?
Less. You may notice that many (all?) microwaves have fans to cool the electronics. That's heat energy that doesn't go into the food. Of course, if you want to use your microwave to heat your room, then it
is 100% efficient...
And smooth top stoves...are they halogen?? How efficient and why??
Resistance heating elements and 100% efficient at producing heat, but not necessarily 100% efficient at transferring it to your food.
