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Homework Help: Why is a Tungsten filament used in incandescent bulbs? (Factual Question)

  1. Jan 14, 2010 #1
    1. The problem statement, all variables and given/known data
    Why is a tungsten filament used in incandescent bulbs?

    I earlier thought that it was due to the high resistivity of tungsten , but i was wrong , the resistivity of tungsten is low at 5.2 * 10^-8 Is it due to its high melting point?? I cant figure out as high melting point doesnt seem to be the only reason for selection of Tungsten.
    Please Help.
    Thank You
     
  2. jcsd
  3. Jan 14, 2010 #2

    mgb_phys

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    What physical properties do you want from a lamp filament ?
    hint - What does Tungsten have the highest of ?
     
  4. Jan 14, 2010 #3
    i think it should be high melting point ( Tungsten has a MP of 3380 C) but again , it has a very low resistivity which means it has a low resistance. So according to Joule's law of heating , a very less amount of heat would be produced . What are your views on this?
     
  5. Jan 14, 2010 #4

    mgb_phys

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    You want less heat - it's wasted energy but that's a secondary point.

    The important point is that to get visible light you need the filament to be as hot as possible, an the lamp will fail when the filament melts - so you need the highest melting point material possible (that is also a conductor of course)
     
  6. Jan 14, 2010 #5
    I get it , so the main reason is melting point! Thanks a ton , i have an exam tommorow , this will surely help!
     
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