# I have purchased four 100W (120V rated) incandescent light bulbs..?

The resistance of these incandescent light bulbs was 8.90 ohms on the average (+/- 0.251 ohms if you want to split some hair): a) How much current will the bulb consume on the average if I plug it in a 120 V circuit? b) How much current will the bulb consume in a 12.0V circuit? (Values are in RMS) How do I do... show more The resistance of these incandescent light bulbs was 8.90 ohms on the average (+/- 0.251 ohms if you want to split some hair):
a) How much current will the bulb consume on the average if I plug it in a 120 V circuit?
b) How much current will the bulb consume in a 12.0V circuit?
(Values are in RMS)
How do I do this problem?
Update: Wiki eloquently states “Incandescence is the release of electromagnetic radiation, usually visible radiation, from a body due to its temperature.” This is the key to the question asked. It is not evident right the way however some of you were quick to point out that 8.90 ohms does not work well in P=V^2/R. R... show more Wiki eloquently states “Incandescence is the release of electromagnetic radiation, usually visible radiation, from a body due to its temperature.” This is the key to the question asked. It is not evident right the way however some of you were quick to point out that 8.90 ohms does not work well in P=V^2/R. R (@120V, 100W)=144 ohms, a 1:16 ratio between cold and hot filament . The question is what makes the resistance rise and remain at that fixed level in our case that being 144 ohms. We have to consider black body (BB) radiation P=ebA(T^4 – Tc^4)
P - Power radiated
e- BB emissivity( 0<e<1)
b- Boltzmann’s constant = 5.670 400(40)×10−8 W/(m^2•K^4).
A – area trough which BB radiates
T- temperature of BB
Tc – temperature of the environment BB radiates
Update 2: References 1. About incandescent light bulb http://physicsed.buffalostate.edu/pubs/TPT/TPTDec99Filament.pdf 2. The physics of an incandescent bulb http://www.sci-ed-ga.org/modules/materialscience/light/ 3. Linear relationship between temperature and resistance... show more References
1. About incandescent light bulb http://physicsed.buffalostate.edu/pubs/T...
2. The physics of an incandescent bulb http://www.sci-ed-ga.org/modules/materia...
3. Linear relationship between temperature and resistance http://www.sci-ed-ga.org/modules/materia...
4. Key black body radiation and ... http://www.millersville.edu/~physics/exp.of.the.month/51/
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