Light AC versus DC

Discussion in 'General Electronics Chat' started by electronewb, Oct 22, 2012.

  1. electronewb

    Thread Starter Member

    Apr 24, 2012
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    Another strange question. Someone at work mentioned that a 35W DC lamp is more powerful than a 35W AC lamp!!!! I thought that power is power!!! One lamp is fed by 120VAC and the other is fed by a 14VDC battery!!
     
  2. wmodavis

    Well-Known Member

    Oct 23, 2010
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    Should be pretty easy to test. The two of you should work together and perform an experiment to determine which is the case. That is how science works. Theory, test.
     
  3. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    But in theory 35W=35W no matter if it AC or DC maybe what he was trying to say is the 14VDC needs less voltage than the 120VAC lamp to get the same wattage. Watt is a unit of measure just like a centimeter 1CM=1CM
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    A low voltage incandescent lamp (doesn't matter if it's AC or DC) can have a higher lumen output than a higher voltage lamp of the same power rating since a lower voltage lamp can have a thicker (lower resistance) filament for a given wattage and thus can be operated at a higher temperature without being too fragile. This gives more light output in the visible and less in the infrared. That's why many of the small halogen lamp fixtures are operated from 12VAC using a line operated transformer instead of directly from the line voltage.
     
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  5. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I have a 35W power resistor and it doesn't give out any light at all.
     
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  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    power is power BUT
    light output versus power is what all the led companies are fighting for now.
    Its the great "Lumens per Watt" competition...
     
  7. wmodavis

    Well-Known Member

    Oct 23, 2010
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    "But in theory 35W=35W no matter if it AC or DC"

    If you are comparing DC power to RMS AC power, you are correct.
     
    PackratKing likes this.
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