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Doesn't Alternating current cause fatigue?

  1. Feb 21, 2008 #1
    Take the case of a lamp bulb. When applied an Alternating current across it.. it basically goes on and off 50 times in a second [in india atleast.. we get 50Hz]. Now, it means that the filament gets hold and cold continuously. From wikipedia:

    so.. is alternating current more damaging for appliances as compared to DC? Almost all electronic devices convert AC to DC.. so they are out of the question... i'm thinking about the rest of the simple devices.. like light bulbs and stuff.
     
  2. jcsd
  3. Feb 21, 2008 #2

    Doc Al

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    Do think that the temperature of the filament has time to change much during each current cycle?
     
  4. Feb 21, 2008 #3
    so.. you basically mean to say that the temperature of the filament remains more or less constant?
     
  5. Feb 21, 2008 #4

    Doc Al

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    I haven't studied the matter, but that's what I would expect. (Where are all the light bulb engineers when you need them?) I would expect most thermal fatigue to occur when you first turn on the bulb.
     
  6. Feb 21, 2008 #5

    Danger

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    That's what I was taught, and empirical evidence seems to support it. I have absolutely never in my life seen a light bulb blow out except when first turned on. That's the same reason that I never shut my computer off; supposedly the thermal expansion/contraction is the main failure point for the internal circuitry. (The HD and screen go to sleep on their own, so I'm not sure that there's any benefit from their perspective.)
     
    Last edited: Feb 21, 2008
  7. Feb 21, 2008 #6
    Well, think about common flicker. We all see it in flourescent bulbs, yet we don't see it in incandescent bulbs.
     
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