Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Incandescent Shape Efficiency

  1. Jan 1, 2010 #1
    Does a 60W Type A (general service) incandescent light bulb put out more light than a 60W Type B (candelabra torpedo) incandescent light bulb?
  2. jcsd
  3. Jan 1, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper

    Not noticably
    There might be slight geometric effects from the distance the filament is from the base an the solid angle that is blocked but compared to the variation in output from tiny changes in the filament resistance these are negligible.
    Remember light output is proportional to the current^4 so variations in this dominate
  4. Jan 1, 2010 #3
    I agree that there shouldn't be any noticeable difference given similar filament shape and temperature between the bulbs, but shouldn't that be current2? The power (light) output would scale with T4, but that power should be coming from joule heating of the filament (I2R).
    Last edited: Jan 1, 2010
  5. Jan 1, 2010 #4
    Ok, thanks.

    These answers seem reasonable. While I'm not sure I would know a correct answer if I saw one, shouldn't this forum have a mechanism by which I can rate the answers? Many forums these days allow the author of a thread to specify one of the replies as a "best answer" to reward the person that provided the most precise/through reply.

    With Respect,

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook