Preferences help
enabled [disable] Abstract
Number of results
2017 | 13 | 52-62
Article title

Cooling-times of tungsten filament lamps

Title variants
Languages of publication
During steady-state operation the hot coiled filaments in incandescent lamps provide luminous flux for illumination, but when it is switched off the temperature as well as the light output drops quite fast. The cooling-time of a lamp is the time required for the hot filament to cool down to ten per cent light output after the circuit is opened. The exercise of estimating luminous flux and cooling-times for typical 10, 100, 500 and 1000 W lamps have been undertaken for the first time for the benefit of students. This problem involves three disciplines electricity, optics and heat. The electricity provides power to heat the filament quickly, followed by optics which helps us in determining the light output and lastly the discipline heat is responsible for cooling the hot filament largely through Stefan-Boltzmann law. It is shown that the supposition of linear configurations for the filaments neither matches luminous flux nor the cooling-times and both fall short. HS Leff suggestion of introducing a shadow factor which reduces the exposed surface area, as it so happens in the coiled filaments, successfully explained the measured observations.
Physical description
  • [1] Incandescent Lamps, Pamphlet TP-110R2 (Nela Park, OH: General Electric Company, 1984) pp. 35, 24
  • [2] The incandescent lamps discussed in the above “bulletin are those that are commonly referred to as “large” lamps. This designation does not necessarily imply large physical size, but refers, usually, to lamps that are operated on standard-voltage circuits, universally found in residential, commercial, and industrial use.” p. 2 in the ref. 1
  • [3] Harvey S. Leff., Illuminating physics with light bulbs, Phys. Teach 28, 30-35 (1990).
  • [4] H. A. Jones and Irving Langmuir, The characteristics of tungsten filaments as functions of temperature: Part II, Gen. Electr. Rev. 30,354-361 (July 1937)
  • [5] M. R. Vukcevich, The Science of Incandescence, (Advanced Technology Department, GE Lighting, Nela Park, Cleveland, 1992), Chapter 9.
  • [6] D. C. Agrawal, H. S. Leff, and V. J. Menon, Efficiency and efficacy of incandescent lamps, Am. J. Phys. 64, 649- 654 (1996)
  • [7] D. C. Agrawal, Moon, Super-Moon, Planets of the Solar System and Star Vega: Brightness and Size. J Phys Astron. 5, 1-20 (2017).
  • [8] R. D. Larrabee, The spectral emissivity and optical properties of tungsten. Technical Report 328, (Research Laboratory of Electronics, MIT, Cambridge, Mass, May 21, 1957)
  • [9] W. H. Stephen and Chun T. Wang Tungsten Sources, Metallurgy, Properties and Applications ( Plenum, New York, 1979) chapter 6
  • [10] W. S. Wagner, Temperature and color of incandescent lamps, Phys. Teach 29, 176-177 (1991).
  • [11] V. J. Menon, and D. C. Agrawal, Lifetimes of incandescent bulbs, Phys. Teach 41, 100-101 (2003).
  • [12] V. J. Menon, and D. C. Agrawal, A theory for the mortality curve of filament lamps, Jour. Mater. Engg. Perf. 16, 1-6 (2007).
  • [13] D. C. Agrawal,and V. J. Menon, Light bulb exponent-rules for the classroom, IEEE Trans. Educ. 43, 262-265 (2000).
Document Type
Publication order reference
YADDA identifier
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.